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Construction of nanofibers from supramolecular self-assembly of Schiff-base macrocycles and metal salphen… Hui, Joseph 2010

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CONSTRUCTION OF NANOFIBERS FROM SUPRAMOLECULAR SELFASSEMBLY OF SCHIFF-BASE MACROCYCLES AND METAL SALPHEN COMPLEXES by JOSEPH KA HO HUI B. Sc. (Hon.), The University of British Columbia, 2001 M. Sc., The University of British Columbia, 2004  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY  in  THE FACULTY OF GRADUATE STUDIES  (Chemistry)  THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) October 2010  © Joseph Ka Ho Hui, 2010  Abstract  The work described in this thesis mainly covers the investigations of a series of conjugated Schiff-base macrocycles and metal salphen complexes. These compounds self-assemble into supramolecular structures through electrostatic or metal-ligand interactions, and their morphologies were studied by electron microscopy and atomic force microscopy. The Schiff-base macrocycles can bind alkali metal and ammonium cations into their crown-ether interior, leading to the formation of one-dimensional columns that can further organize into nanofibers with hierarchical organization. However, when macrocycles appended with long alkoxy chains were treated with the same conditions, lyotropic liquid crystallinity in organic solvents was observed under a polarized optical microscope. Among the metallosalphen complexes prepared, zinc(II)containing salphen complexes were found to assemble into helical fibrous structures and exhibit gelation behavior in various solvents. Furthermore, modification of the peripheral substituents of the zinc(II) salphen complexes with carbohydrates further enhanced the helicity in the nanofibers. In addition, the surface texture and diameter of the nanofibers can be altered by the presence of ditopic 4,4′-bipyridine and the increase in hydrophobic effects during sample preparation.  ii  Table of Contents Abstract ...............................................................................................................................ii Table of Contents...............................................................................................................iii List of Tables .....................................................................................................................vi List of Figures ...................................................................................................................vii List of Schemes..............................................................................................................xviii List of Symbols and Abbreviations..................................................................................xix Acknowledgements........................................................................................................xxiv Co-Authorship Statement...............................................................................................xxvi CHAPTER 1 1.1 1.2  1.3  1.4 1.5  Introduction to Nanofibers........................................................................................1 Nanofibers Constructed from Macorcyclic Units .....................................................5 1.2.1 Metalloporphyrins and Metallophthalocyanines .........................................5 1.2.2 Ion-induced Self-assembly ........................................................................15 Nanofibers Obtained from Coordination Polymers ................................................19 1.3.1 Metal-ligand Coordination.........................................................................20 1.3.2 Static Coordination Polymer Gels .............................................................24 1.3.3 Dynamic Coordination Polymer Gels........................................................32 Goals and Scope of This Thesis..............................................................................52 References...............................................................................................................56  CHAPTER 2 2.1  Introduction...............................................................................................1  [6+6] Schiff-base Macrocycles ...............................................................65  Introduction.............................................................................................................65 iii  2.2 2.3 2.4 2.5  Results and Discussion ...........................................................................................66 Conclusions.............................................................................................................75 Experimental ...........................................................................................................76 References...............................................................................................................82  CHAPTER 3  3.1 3.2  Introduction.............................................................................................................86 Results and Discussion ...........................................................................................89 3.2.1 Synthesis and Characterization of Nanofibers from Macrocycle 3.2.2  3.3 3.4 3.5  Ion-induced Self-assembly of [3+3] Schiff-base Macrocycles into Lyotropic Liquid Crystals..............................................................118  Introduction...........................................................................................................118 Results and Discussion .........................................................................................120 Conclusions...........................................................................................................127 Experimental .........................................................................................................128 References.............................................................................................................130  CHAPTER 5 5.1 5.2 5.3 5.4 5.5  42 with Sodium Salts .................................................................................89 Synthesis and Characterization of Nanofibers from Macrocycle  42 with Ammonium Salts ........................................................................102 Conclusions...........................................................................................................105 Experimental .........................................................................................................106 References.............................................................................................................113  CHAPTER 4  4.1 4.2 4.3 4.4 4.5  Ion-induced Self-assembly of [3+3] Schiff-base Macrocycles into Nanofibers with Hierarchical Organization.....................................86  Self-assembly of Zinc(II) Salphen Complexes into Nanofibers ...........132  Introduction...........................................................................................................132 Results and Discussion .........................................................................................133 Conclusions...........................................................................................................144 Experimental .........................................................................................................145 References.............................................................................................................159  iv  CHAPTER 6  6.1 6.2  6.3 6.4 6.5  Introduction...........................................................................................................162 Results and Discussion .........................................................................................165 6.2.1 Synthesis and Characterization of Metallosalphen Complexes 43f,g, 54c,d, and 58a–f............................................................................165 6.2.2 Morphological study of the Supramolecular Self-assemblies of the Metal Salphen Complexes .................................................................171 Conclusions...........................................................................................................178 Experimental .........................................................................................................178 References.............................................................................................................202  CHAPTER 7  7.1 7.2  Complexes 44a–d ....................................................................................210 Morphological study of the Supramolecular Structures of the  Dinuclear Zinc(II) Salphen Complexes 44a–d........................................218 7.2.3 Change in the Surface Morphology with the Addition of 4,4′Bipyridine ................................................................................................224 Conclusions...........................................................................................................228 Experimental .........................................................................................................229 References.............................................................................................................244  CHAPTER 8 8.1 8.2 8.3  Self-assembly of Dinuclear Zinc(II) Salphen Complexes into Helical Nanofibers ................................................................................207  Introduction...........................................................................................................207 Results and Discussion .........................................................................................210 7.2.1 Synthesis and Characterization of Dinuclear Zinc(II) Salphen 7.2.2  7.3 7.4 7.5  Self-assembly of Carbohydrate-functionalized Zinc(II) Salphen Complexes into Helical Nanofibers ......................................................162  Conclusions and Future Directions.......................................................249  Overview...............................................................................................................249 Future Directions ..................................................................................................252 References.............................................................................................................259  v  List of Tables  Table  5.1 Gel forming abilities of complexes 43a–e in various solvents. ................135  vi  List of Figures Figure 1.1. Chemical structures of porphyrins 1 and 2. ..................................................7 Figure 1.2. (a) TEM and (b) SEM images of the bundles of porphyrin nanofibers. Copyright Wiley-VCH Verlag GmbH and Co. KGaA. Reproduced with permission from reference 36. ..........................................7 Figure 1.3. TEM image of the porphyrin nanofibers. Reproduced with permission from reference 37. Copyright 2001 The Chemical Society of Japan. .........................................................................................10 Figure 1.4. Chemical structure of phthalocyanines 5a and 5b. .....................................11 Figure 1.5. TEM images of samples of 5a prepared from chloroform at concentrations of (a) 1 x 10-5 M and (b) 1 x 10-6 M. Reproduced with permission from reference 39. Copyright 2007 American Chemical Society...............................................................12 Figure 1.6. Chemical structures of MgPc(SEtPh)8 complexes 6a–6c. ..........................14 Figure 1.7. (a) Schematic representation of the helical arrangement of the interfacial J-aggregate of MgPc(SEtPh)8-Pd(II) polymeric structure (MgPc(SEtPh)8 = squares, PdCl2 = spheres). FE-SEM images of the interfacial aggregate of (b) (R)-MgPc(SEtPh)8-Pd(II) and (c) (S)-MgPc(SEtPh)8-Pd(II) complexes. Twisted fibers can be clearly seen in (c). Reproduced with permission from reference 41. Copyright 2006 American Chemical Society. ......................................14 Figure 1.8. Chemical structure of macrocycle 7............................................................16 Figure 1.9. (a) Schematic representation of the presumed aggregation process of macrocycle 7 with K+ ions. (b) TEM image of macrocycle 7b with K+ prepared in chloroform/nitromethane. Reproduced with vii  permission from reference 43. Copyright 2008 American Chemical Society. .......................................................................................16 Figure 1.10. Chemical structures of guanosines 8 and 9, and a G-quartet. ....................18 Figure 1.11. Visual appearance of the hydrogels obtained from guanosine 8 and guanosine 9 in aqueous potassium chloride solution (a) 15 min and (b) 36 h after sample preparations. The ratios are listed as guanosine 8/guanosine 9. (c,d) AFM images of the 60/40 and 40/60 gels, respectively. Reproduced with permission from reference 47. Copyright 2009 American Chemical Society........................19 Figure 1.12. Chemical structures of π-conjugated donor 10 and acceptor 11. ................21 Figure 1.13. (a) TEM and (b) SEM images of the nanofibers. (c) Schematic representation of the coordination-assisted self-assembly mechanism. Reproduced with permission from reference 51. Copyright 2009 American Chemical Society. ......................................21 Figure 1.14. (a–h) SEM images monitoring the transformation of nanowires into nanocubes. Copyright Wiley-VCH Verlag GmbH and Co. KGaA. Reproduced with permission from reference 52.............................23 Figure 1.15. Chemical structure of compound 13. ..........................................................25 Figure 1.16. (a) Photograph of metallogels with metal/13 of 1:4 (left), 1:2 (middle) and 1:1 (right). SEM images of xerogels with (b) fibrous, (c) spherical, and (d) porous structures. Reproduced with permission from reference 54. Copyright 2009 American Chemical Society. .......................................................................................25 Figure 1.17. Chemical structures of bisimidazole 14 and bisbenzimidazole 15. ............27 Figure 1.18. (a) Schematic representation of the formation of the helical coordination polymer gelators formed from 14 and 15. (b) TEM image of the dried gel (the sample was negatively stained with viii  uranyl acetate solution). The inset is a magnified image of the marked area. (c) AFM (height trace, tapping mode) image of the dried gel on a mica surface. (d) A magnified AFM image of the marked area. (e) SEM image of the xerogel stained with gold. Reproduced with permission from reference 55. Copyright 2008 The Royal Society of Chemistry. ................................................................27 Figure 1.19. Chemical structure of 4,4′-bis(1-imidazolyl)biphenyl (bibp, 16). .............29 Figure 1.20. (a) SEM image of the sheet-like microparticles formed from 16 before sonication. (b) Crystal structure of tetrahedral zinc(II) center with four bibp (16) units. (c) Two-dimensional coordination network. (d) A suspension before sonication (left) and an opaque white gel after sonication (right). (e) TEM image of the gel (negatively stained with uranyl acetate). (f) SEM image of the xerogel. (g) Metal coordination geometry is tetrahedral in the sheet-like microparticles and see-saw in the nanofibers. Reproduced with permission from reference 56. Copyright 2009 American Chemical Society........................................................................30 Figure 1.21. Chemical structure of the free ligand 17 and schematic representation of the proposed coordination polymer 18............................32 Figure 1.22. (a) Photograph of ligand 17 in water (left) and hydrogel (right). (b) SEM and (c) TEM images of the xerogel of coordination polymer 18. Copyright Wiley-VCH Verlag GmbH and Co. KGaA. Reproduced with permission from reference 57. ........................................32 Figure 1.23. Chemical stoichiometries of lipophilic cobalt(II) complexes 19 and 20, and ligands 21 and 22. ..........................................................................34 Figure 1.24. Photographs of complex 20 in chloroform at (a) 25 ºC (blue gel) and (b) 0 ºC (pale pink solution). (c) AFM and (d) TEM images of complex 20. (e) TEM image of complex 19. (f) SEM image of the xerogel of complex 20. Schematic representations of (g) polymeric Td complex and (h) polymeric Oh complex. Reproduced with ix  permission from reference 61. Copyright 2004 American Chemical Society. TEM images of complex 20 with (i) 1-dodecanol and (j) 1,12-dodecanediol. Reproduced with permission from reference 62. Copyright 2008 The Chemical Society of Japan...................................35 Figure 1.25. Chemical stoichiometry of lipophilic iron(II) complex 23. ........................37 Figure 1.26. Schematic representations of (a,b) the lipophilic polymeric iron(II) complex 23. (c) The yellow gel (20 ºC in chloroform) and TEM image of complex 23. Photographs of cast films at (d) 20 and (e) 80 ºC. (f) Schematic representation of the long-chained alcohols hydrogen-bonded to the chloride counteranions. Copyright 2006; Reproduced with permission of John Wiley & Sons, Inc from reference 63. ...............................................................................................37 Figure 1.27. Chemical stoichiometries of lipophilic iron(II) complexes 24 and 25. ...............................................................................................................38 Figure 1.28. AFM images of complex 24 in the (a) LS and (b) HS states, and complex 25 in the (c) LS and (d) HS states. Reproduced with permission from reference 64. Copyright 2008 The Chemical Society of Japan. ........................................................................................39 Figure 1.29. Chemical structures of ligand 26 and stoichiometry lipophilic iron(II) complex 27. ....................................................................................41 Figure 1.30. (a) Schematic representation of lipophilic polymeric iron(II) complex 27. (b) AFM of the sample prepared in chloroform. (c–f) Photographs of complex 27 in chlorocyclohexane at room temperature: (c) before irradiation, (d) after irradiation with UV light (365 nm), (e) after irradiation with visible light (546 nm), and (f) after storage in the dark for 25 min. (g) SEM of the xerogel. (h) AFM of the sample prepared in chlorocyclohexane (h) before and (i) 2 min after irradiation with UV light (365 nm). Reproduced with permission from reference 65. Copyright 2006 The Royal Society of Chemistry. .................................................................................41 x  Figure 1.31. Chemical stoichiometries of lipophilic iron(II) complexes 28 and 29. ...............................................................................................................43 Figure 1.32. (a) Schematic representation of the reversible LS-HS transition with cooling and heating cycles. AFM images of complex 28 in the (b) LS and (c) HS states, and complex 29 in the (d) LS and (e) HS states. Reproduced with permission from reference 66. Copyright 2008 American Chemical Society. ......................................43 Figure 1.33. Chemical structures of lipid counteranions 30–37. ....................................45 Figure 1.34. Schematic representation of polymeric platinum complexes with lipid counteranions. Reproduced with permission from reference 67b. Copyright 1998 The Chemical Society of Japan.................................45 Figure 1.35. TEM images of the mixed valence platinum complexes with lipid counteranions (a) 30, (b) 32, (c) 34, (d) 35, (e) 36, (f) 37 in chloroform, (g) 37 in dichloromethane, (h) 34 at 60 ºC, (i) 34 after cooling from 60 ºC to room temperature, and (j) 30 after cooling from 60 ºC to room temperature, respectively. (k) Schematic representation of the reversible dissociation/re-assembly process. (a,c–e,h–k) Reproduced with permission from reference 67a. Copyright 2000 American Chemical Society. (b) Reproduced with permission from reference 67b. Copyright 1998 The Chemical Society of Japan. (f,g) Reproduced with permission from reference 67c. Copyright 2002 The Chemical Society of Japan. ..........................................................................................................47 Figure 1.36. Chemical structure of lipid counteranion 38. .............................................48 Figure 1.37. TEM images of the samples prepared in dichloromethane: (a) [Pt(en)2](38)2, (b) 6:1, (c) 3:1, and (d) 2:1 of [Pt(en)2](38)2/HAuCl4. Reproduced with permission from reference 69. Copyright 2005 The Chemical Society of Japan...................49 Figure 1.38. Chemical structure of lipid counteranion 39. .............................................50 xi  Figure 1.39. (a,b) TEM images of [Pt(en)2][PtCl2(en)2](39)4 prepared at 0 ºC. (c) TEM and (d) SEM images of the sample prepared at 21 ºC. Reproduced with permission from reference 70. Copyright 2002 National Academy of Sciences, U.S.A.. ....................................................51 Figure 1.40. Chemical structures of Schiff-base macrocycles 40–42. ...........................54 Figure 1.41. Chemical structures of zinc(II) salphen complexes 43–44. .......................55 Figure 2.1. Chemical structures of [6+6] Schiff-base macrocycles 40 and 41. ............66 Figure 2.2. MALDI-TOF mass spectra of (a) crude reaction mixture from the preparation of macrocycle 40a and (b) purified macrocycle 40a. Insets: top (black): Isotope distribution obtained for macrocycle 40a; bottom (red): isotope distribution calculated for (40a+H)+. ..............68 Figure 2.3. Fragments observed in MALDI-TOF mass spectrum of crude macrocycle 40a. .............................................................................................. 71 Figure 2.4. MALDI-TOF mass spectrum of macrocycle 48. ........................................72 Figure 2.5. Chemical structure of macrocycle 48..........................................................73 Figure 2.6. Chemical structure of compound 49. ..........................................................74 Figure 2.7. Calculated structure of macrocycle 40c metallated with six nickel(II) ions (PM3): (a) view of chair (D3d) conformation; (b) view of boat (C2v) conformation. The hydrogen atoms have been removed for clarity. (Color legend: blue = nitrogen, gray = carbon, green = zinc and red = oxygen) ..................................................................75 Figure 3.1. Chemical structure of [3+3] Schiff-base macrocycle 42. ...........................89 Figure 3.2. (a,b) TEM, (c,d) SEM, and (e,f) AFM micrographs of [Na·42a]BF4. All samples were prepared by drop-casting a chloroform solution of [Na·42a]BF4 onto formvar carbon-coated xii  grids (TEM and AFM) or aluminum stubs (SEM) and dried at ambient condition. ......................................................................................91 Figure 3.3. Representative TEM image of macrocycle 42a deposited on a TEM grid without any salts. .................................................................................... 92 Figure 3.4. Powder XRD patterns of [Na·42a]BF4 (blue), macrocycle 42a (black) and NaBF4 (red). .............................................................................93 Figure 3.5. IR spectra of macrocycle 42a (red) and [Na·42a]BF4 (blue). Inset: expanded view of imine stretching band. ...................................................94 Figure 3.6. Solid-state 23Na NMR spectra acquired with and without proton decoupling (dashed line and solid line, respectively) of (a) [Na·42a]BF4 and (b) [Na·42a]BF4 with hydroxyl deuterons. c) Solid-state 2H NMR spectra acquired at 21 and -50 oC. d) Solidstate 11B NMR spectrum of [Na·42a]BF4. .................................................96 Figure 3.7. ESI mass spectrum of [Na·42a]BF4 in methanol/methylene chloride mixture. .........................................................................................97 Figure 3.8. TEM image of macrocycle 51 with NaBF4. ...............................................99 Figure 3.9. (a,b) TEM images of macrocycle 42a with NaBPh4. ...............................100 Figure 3.10. (a,b) The solvent was evaporated in 10 sec at 92 oC. (c,d) The sample was dried inside a vial (in 80–90 min), which helped to slow down the evaporation of the solvent. ........................................................... 101 Figure 3.11. (a) Optical, (b,c) TEM, (d,e) SEM, and (f,g) AFM (height trace and amplitude trace, respectively) micrographs of macrocycle 42a with NH4BF4. The sample has been negatively-stained with chromium for better contrast in (e). ..........................................................103 Figure 3.12. (a–c) Optical micrographs of the microfibrils from macrocycle 42a and NH4BF4 under the crossed polarizers. ...............................................104 xiii  Figure 3.13. A graphic representation of the four-level hierarchical assembly. In the first step, dialdehyde and diamine precursors assemble into macrocycles. Upon reaction with NH4BF4, these form polyelectrolytes that organize into nanofibers. In the final step, the nanofibers bundle into microfibers. ..........................................................105 Figure 4.1. Chemical structure of macrocycle 42 with long alkoxy substituents. ..............................................................................................119 Figure 4.2. Optical micrographs of chloroform solutions of NH4BF4 with macrocycles (a) 42c, (b) 42e and (c,d) 42d (1:1 ratio of 42:NH4+) show typical textures observed for the LC samples under crossed polarizers. Samples were viewed between a slide and a cover slip as the solvent evaporated from samples that were ca. 10 wt%. ...............121 Figure 4.3. Ion-induced assembly leading to the formation of lyotropic liquid crystals. (a) In solvent, macrocycle 42c–e combine with cations (yellow spheres) to form a one-dimensional polymeric structure where the macrocycles are bridged by the cations. (b) Upon concentration, these one-dimensional assemblies organize into a nematic liquid crystal phase where they retain orientational order. The counteranions have been omitted for clarity. ....................................... 122 Figure 4.4. Optical micrographs of macrocycle 42c with (a) LiBF4 in chloroform, (b) NaBF4 in chloroform, (c) NH4BF4 in toluene, and (d) NH4BF4 in chlorobenzene. .................................................................124 Figure 4.5. Powder XRD patterns of (a) macrocycles 42c–e with NH4BF4 and (b) macrocycle 42c with NH4BF4, LiBF4 and NaBF4. ............................126 Figure 4.6. Model of four molecules of macrocycle 42c in the same plane; center-to-center distances to the middle macrocycle in the model are ca 28 Å apart. If each macrocycle represents an ion-induced tubular assembly of macrocycles, then this separation between the columns is reasonable. .............................................................................127 xiv  Figure 5.1. Chemical structure of zinc(II) salpen complexes 43. ...............................133 Figure 5.2. (a) Photograph of the gel of complex 43a in methanol under visible light (left) and when irradiated with UV light (right). (b) Fiber morphology of complex 43a cast from methanol, as observed by TEM. ....................................................................................134 Figure 5.3. TEM images of complexes (a) 43a, (b) 43b, (c) 43c, (d) 43e, and (e,f) 43d deposited from methanol. ..........................................................136 Figure 5.4. Powder XRD pattern of complex 43c. .........................................................137 Figure 5.5. TEM images of complexes (a,b) 43f and (c,d) 43g deposited from methanol. ..................................................................................................138 Figure 5.6. Chemical structures of nickel(II) salphen complexes 54a–d, and zinc(II) salphen complexes 55 and 56. .....................................................139 Figure 5.7. TEM images of nickel(II) complexes (a) 54a, (b) 54b deposited from methanol/tetrahydrofuran and (c) 54c, (d) 54d deposited from methanol. .........................................................................................140 Figure 5.8. UV/Vis and fluorescence spectroscopy of complex 43a in methylene chloride and in the solid state (gel). ........................................141 Figure 5.9. ESI mass spectrum of complex 43c exhibits singly (red) and doubly (blue) charged species. A: [43c+Na]+, B: [43c2+Na]+, C: [43c3+Na]+, D: [43c4+Na]+, E: [43c5+Na]+, F: [43c3+Na2]2+, G: [43c5+Na2]2+, H: [43c7+Na2]2+, I: [43c9+Na2]2+. ......................................142 Figure 5.10. Energy-minimized (PM3) calculated structure for a heptamer of zinc(II) salphen complex. (a) The entire oligomer containing seven zinc(II) salphen molecules connected into a one-dimensional structure. (b) An expanded view of three zinc(II) salphen complexes from the middle of the heptamer. (Color legend: carbon = green, nitrogen = blue, oxygen = red, zinc = grey) ................................................ 143 xv  Figure 6.1. Chemical structures of salphen complexes 43f,g, 54c,d, and 58a–f. ...................................................................................................................164 Figure 6.2. (a) Top view and (b) side view of the crystal structure of acetylprotected galactose-functionalized dinitrobenzene 61b. The hydrogen atoms have been removed for clarity, except the anomeric hydrogen in the side view to show the β-conformation. The acetyl-protecting groups are also removed for clarity in the side view. (Color legend: carbon = black, hydrogen = white, nitrogen = blue, oxygen = red) .................................................................167 Figure 6.3. TEM images of (a–e) glucose-functionalized metal salphen complexes 58a, 58c, 54c, 58e and 43f and (f–j) galactosefunctionalized metal salphen complexes 58b, 58d, 54d, 58f and 43g, respectively. ......................................................................................172 Figure 6.4. AFM images of (a–e) glucose-functionalized metal salphen complexes 58a, 58c, 54c, 58e and 43f, respectively. Insets of (e) top: a closer look of the rectangular-boxed region; bottom, a histogram of the widths of 100 nanofibers counted in (e). ......................174 Figure 6.5. Graphic representation of the helicity in the fibers of zinc(II) salphen complex 43f. ...............................................................................175 Figure 6.6. TEM images of the gels of (a) acetyl-protected glucosefunctionalized nickel(II) salphen complex 62b and (b) diluted in methanol; (c) acetyl-protected galactose-functionalized copper(II) salphen complex 63e and (d) diluted in methanol. ...................................177 Figure 7.1. Chemical structure of dinuclear zinc(II) salphen 44. ...............................210 Figure 7.2. Solid-state structure of bis(zinc(II) salphen) complex 44c·2DMSO as determined by single crystal XRD. (a) Top view and (b,c) side views of the molecular structure. The hydrogen atoms have been removed for clarity. (Color legend: carbon = gray, nitrogen = nitrogen, oxygen = red, sulphur = yellow, zinc = pink) ...........................214 xvi  Figure 7.3. ESI mass spectrum of bis(zinc(II) salphen) complex 44a. ......................215 Figure 7.4. UV-Vis spectra for the titration of bis(zinc(II) salphen) complex 44d (6.05 μM in chloroform) with DMSO. ................................................. 217 Figure 7.5. TEM images of salphen complexes 44a–d in (a–d) methanol, (e– h) chloroform, and (i–l) methanol/chloroform mixture, respectively. .............................................................................................221 Figure 7.6. Higher magnification TEM images of complexes 44c and 44d in (a,b) methanol and (c,d) methanol/chloroform mixture, respectively. .............................................................................................222 Figure 7.7. (a,b) TEM and (c,d) SEM images of salphen complex 44d precipitated from 1:3 chloroform/methanol mixture. The SEM samples are coated with gold/palladium for imaging. .............................224 Figure 7.8. (a,b) TEM images of complex 44d with 4,4′-bipyridine drop-cast from methanol/chloroform mixture. (b) is the magnified view of (a). (c,d) TEM and (e,f) SEM images of the yellow precipitate. The SEM samples are coated with gold/palladium for imaging. (The short fibers in the background of (d–f) are from the fibrous aggregates that were still in solution before drop-casting the precipitate onto the grid.) .........................................................................226 Figure 7.9. Powder XRD patterns of the precipitate obtained when complex 44d is combined with 4,4′-bipyridine (top), complex 44d (middle), and 4,4′-bipyridine (bottom). ...................................................................228 Figure 8.1. Calculated structure of [2+2] Schiff-base macrocycle 71. Please note that the hexyloxy chains were removed for clarity. .........................254 Figure 8.2. Chemical structure of [2+2] Schiff-base macrocycle 72. .........................255  xvii  List of Schemes  Scheme 1.1. Synthesis of porphyrin coordination polymer 4. ..........................................9 Scheme 1.2. Salphen 11 combines with zinc(II) to form nanowires and nanocubes, with the chemical structure depicted by 12. Copyright Wiley-VCH Verlag GmbH and Co. KGaA. Reproduced with permission from reference 52. ....................................................................23 Scheme 2.1. Synthetic route to air-stable compound 47. ................................................67 Scheme 3.1. Syntheses of (a) macrocycle 51 and (b) 1,4-diformyl-2,3dihydroxytriptycene (50).............................................................................99 Scheme 5.1. Synthesis of zinc(II) salphen 56. ..............................................................157 Scheme 6.1. Syntheses of dinitrobenzenes 61 and phenylenediamines 46g,h. .............166 Scheme 6.2. Syntheses of acetyl-protected metal salphen complexes 62 and 63, and metal salphen complexes 43f,g, 54c,d, and 58a–f. ...........................169 Scheme 6.3. Syntheses of the new phenylenediamines 46i,j. .......................................170 Scheme 7.1. Syntheses of compounds 65–68. ..............................................................212 Scheme 8.1. Syntheses of compound 70 and [2+2] Schiff-base macrocycle 71. .........254 Scheme 8.2. Proposed synthetic route to metallated salphen complexes 73 and 74. .............................................................................................................256 Scheme 8.3. Proposed synthetic route to [3+3] Schiff-base macrocycle 79. ................258  xviii  List of Symbols and Abbreviations  Abbreviation  Description  [X+X]  this notation throughout the thesis refers to a Schiff-base macrocycle formed by the condensation of X diamine moieties with X dialdehyde moieties  Å  Ångström  δ  chemical shift  υ  frequency  λ  wavelength  λmax  wavelength at local maxima  ε  molar extinction coefficient (cm-1 mol-1 L)  acac  acetylacetonate  AFM  atomic force microscopy  Anal. Calc’d  analytical calculated  Anth-SO3-  9,10-dimethoxyanthracene-2-sulfonate  APCI  atmospheric pressure chemical ionization  arb. unit  arbitrary unit  bibp  4,4′-bis(1-imidazolyl)biphenyl  bipy  4,4′-bipyridine  n-BuLi  n-butyllithium  CD  circular dichroism  xix  COD  cycloocta-1,5-diene  CT  charge transfer  d  doublet (for NMR), day  d  deuterium  DDQ  2,3-dichloro-5,6-dicyanobenzoquinone  DMF  N,N-dimethylformamide  DMSO  dimethylsulfoxide  EA  elemental analysis  EDX  energy dispersive X-ray  EI  electron impact  en  ethylenediamine  equiv.  equivalent  ESI  electrospray ionization  Et2O  diethyl ether  EtOH  ethanol  FE  field emission  FT  Fourier transform  hex  hexanes  HR-EI  high resolution electron impact  HR-ESI  high resolution electrospray ionization  HS  high spin  IR  infrared  LC  liquid crystal  LS  low spin xx  M  molar (mol L-1)  m  multiplet (for NMR), medium (for IR)  MALDI  matrix-assisted laser desorption ionization  MeCN  acetonitrile  MeOH  methanol  [MgPc(SEtPh)8]  (2,3,9,10,16,17,23,24-octakis-1-phenylethylthiophthalocyaninato)magnesium(II)  mmol  millimole  mmol%  millimole percent  mol  mole  mol. wt.  molecular weight  m.p.  melting point  MS  mass spectrometry  [MTPPS]4-  metallo tetrakis(4-sulfonatophenyl)porphyrin  m/z  mass-to-charge ratio  N2O2  tetradentate coordination site of salphen  Nc  columnar nematic  NMR  nuclear magnetic resonance  o  ortho  Oh  octahedral  p  para  Ph  phenyl  PM3  Parameterized Model number 3  xxi  POM  polarizing optical microscopy or polarizing optical microscope  ppm  parts per million  Py-SO3-  1-pyrenesulfonate  q  quartet (for NMR)  i-PrOH  isopropanol  s  singlet (for NMR), strong (for IR)  salen  N,N′-bis(salicylidene)ethylenediamine  salphen  N,N′-bis(salicylidene)-o-phenylenediamine  [SbOTPP]+  oxo-antimony(V) tetraphenylporphyrin  SEM  scanning electron microscopy  T  temperature  t  triplet (for NMR)  Td  tetrahedral  TEM  transmission electron microscopy  TEOS  tetraethyl orthosilicate  THF  tetrahydrofuran  TMEDA  N,N,N′,N′-tetramethylethylenediamine  TOF  time of flight  υ  wavenumber (cm-1)  UV-vis  ultraviolet-visible  V  volume  v/v  volume-to-volume ratio  vs  very strong (for IR) xxii  w  weak (for IR)  wt%  weight percentage  XRD  X-ray diffraction  xxiii  Acknowledgements  I would like to thank my EXCELLENT supervisor Professor Mark MacLachlan for his guidance throughout my PhD work. Mark is a super enthusiastic person about chemistry, an exceptional teacher and a great friend both inside and outside the lab. He made all challenging projects seem possible to overcome with plenty of valuable advice and support. I am so glad to have the opportunity to work for him for the past ten years, including my MSc study. I am also grateful to have an awesome experience to work with all members (both past and present) from the MacLachlan group. It was pleasant to have them around throughout my time in the group with their profuse love, encouragement and support. I have had a lot of good times with them, both inside and outside the lab. Professor Chris Orvig carefully read through the rough draft of this thesis and his advice was greatly appreciated. Also, my PhD work would not have been successful without the help and contributions of the staffs and members in the Chemistry Department of UBC, and our collaborators. I want to especially thank the members in the Wolf group for their time and efforts when I needed help, everyone of the UBC Microanalytical Services Laboratory for obtaining the mass spectra and elemental analyses, and Brad Ross, Derrick Horne and Garnet Martens of the UBC BioImaging Services Laboratory for their assistance and patience in teaching me all the skills and tricks I need to collect all the micrographs.  I would like to give a big “thank you” to my family and friends for their love and support throughout these long years of study and research. Last but not least, I want to  xxiv  thank my lovely, gorgeous girlfriend Jessica for her unconditional love, patience and support at the final stage of my PhD study.  xxv  Co-Authorship Statement  A version of Chapter 1 has been published as a review article and this is the pre-peer reviewed version of the following article: Hui, J. K.-H.; MacLachlan, M. J. “MetalContaining Nanofibers via Coordination Chemistry” Coord. Chem. Rev. 2010, 254, 2363. I wrote the first draft of this review article and edited it with Professor Mark MacLachlan.  A version of Chapter 2 has been published as a communication and this is the prepeer reviewed version of the following article: Hui, J. K.-H.; MacLachlan, M. J. “[6+6] Schiff-base Macrocycles with 12 Imines: Giant Analogues of Cyclohexane” Chem. Commun. 2006, 2480. I wrote the first draft of this paper and conducted all of the experiments under the supervision of Professor Mark MacLachlan. He performed the computational modellings of Figure 2.7.  A version of Chapter 3 has been published as an article and this is the pre-peer reviewed version of the following article: Hui, J. K.-H.; Frischmann, P. D.; Tso, C.-H.; Michal, C. A.; MacLachlan, M. J. “Spontaneous Hierarchical Assembly of Crown Etherlike Macrocycles into Nanofibers and Microfibers Induced by Alkali Metal and Ammonium Salts” Chem. Eur. J. 2010, 16, 2453. I wrote the first draft of this paper and conducted all of the experiments under the supervision of Professor Mark MacLachlan. Peter Frishmann was a PhD student who synthesized Schiff-base macrocycle 51. Jenny Tso was a PhD student of our collaborator Professor Carl Michal who performed the solid-state  NMR  experiments  of  Schiff-base  macrocycle  42a  with  sodium  xxvi  tetrafluoroborate. SEM images were obtained by our PhD student Kevin Shopsowitz and Tim Kelly, a PhD student of our collaborator Professor Michael Wolf. Tissaphern Mirfakhrai was a PhD student of our collaborator Professor John Madden who obtained the AFM micrographs. Usama Al-Atar, a PhD student of Simon Fraser University, performed the particle size measurements.  A version of Chapter 4 will be submitted for publication as a communication: Hui, J. K.-H.; MacLachlan, M. J. “Ion-Induced Columnar Assembly of Lyotropic Ionic Liquid Crystals from Schiff-base Macrocycles”. I wrote the first draft of this paper and conducted all of the experiments under the supervision of Professor Mark MacLachlan. He performed the drawing for ion-induced assembly of Figure 4.3  A version of Chapter 5 has been published as a communication and this is the prepeer reviewed version of the following article: Hui, J. K.-H.; Yu, Z.; MacLachlan, M. J. “Supramolecular Assembly of Zinc Salphen Complexes: Access to Metal-Containing Gels and Nanofibers” Angew. Chem. Int. Ed. 2007, 46, 7980. I wrote the first draft of this paper and conducted all of the experiments under the supervision of Professor Mark MacLachlan. He performed the computational modellings of Figure 5.10.Richard Yu was an exchange student from the National University of Singapore who contributed to the synthesis of some metal salphen complexes under my guidance.  A version of Chapter 6 has been published as an article and this is the pre-peer reviewed version of the following article: Hui, J. K.-H.; Yu, Z.; Mirfakhrai, T.; MacLachlan, M. J. “Supramolecular Assembly of Carbohydrate-Functionalized Salphenxxvii  Metal Complexes” Chem. Eur. J. 2009, 15, 13456. I wrote the first draft of this paper and conducted all of the experiments under the supervision of Professor Mark MacLachlan. Richard Yu was an exchange student from the National University of Singapore who contributed to the synthesis of some metal salphen complexes under my guidance. Tissaphern Mirfakhrai was a PhD student of our collaborator Professor John Madden who obtained the AFM micrographs. Jonathan Chong was a PhD student who solved the crystal structure of compound 61b in Figure 6.2.  A version of Chapter 7 has been published as an article and this is the pre-peer reviewed version of the following article: Hui, J. K.-H.; MacLachlan, M. J. “Fibrous Aggregates from Dinuclear Zinc(II) Salphen Complexes” Dalton Trans. 2010, 7310. I wrote the first draft of this paper and conducted all of the experiments under the supervision of Professor Mark MacLachlan. SEM images were obtained by our PhD student Kevin Shopsowitz and UBC BioImaging Facility technician Derrick Horne. Peter Frishmann was a PhD student who solved the crystal structure of complex 44c in Figure 7.2.  xxviii  CHAPTER 1 INTRODUCTION †  1.1 Introduction to Nanofibers  The field of nanochemistry is rapidly expanding, and will lead to facile routes to construct sophisticated nanoscale materials. 1 This “bottom-up” approach has many benefits over traditional “top-down” approaches (e.g., lithography) as it enables more control of the molecular architecture and assembly of more sophisticated structures. Over the past several decades, supramolecular self-assembly has emerged as a powerful technique for the construction of complicated, often hierarchical materials with significant functions and properties. The utility of supramolecular chemistry in the construction of nanomaterials and devices is well-exemplified by recent work in the literature, including the one-pot, 18-component assembly of diformylpyridine, 2,2′-bipyridine-containing diamine and zinc ions into three macrocycles that interlock into the shape of a Borromean ring, 2 the self-assembly of tris-2,2′-bipyridine and iron(II) chloride into a circular double helicate, 3 conjugated polyrotaxanes composed of cyclodextrin  with  threads  based  on  poly(p-phenylene),  polyfluorene,  and  poly(diphenylenevinylene) and stoppered with naphthalene groups, 4 and the family of metal-organic frameworks with metal-oxygen polyhedra linked by bridging ligands. 5  †  A version of this chapter has been published as a review article: Hui, J. K.-H.; MacLachlan, M. J.  “Metal-Containing Nanofibers via Coordination Chemistry” Coord. Chem. Rev. 2010, 254, 2363.  1  The applications of nanostructured supramolecular assemblies depend on the shapes and their functionalities, which can be imparted by selection of molecular precursors. For instance, bowl-shaped complexes can self-organize into nanocapsules for host-guest chemistry 6 and structures shaped like badminton shuttlecocks can organize into one-dimensional columnar structures. 7 By choosing precursors with specific geometries, nanostructures with particular forms may be anticipated. However, it is often by chance that new nanomaterials are discovered, and their shapes may not be obvious extensions of the molecular geometry.  Nanofibers are an exciting class of materials with excellent potential for real applications, fundamental investigations, and for understanding biological systems. They are long-range-ordered, one-dimensional, nanosized supramolecular aggregates that can be linear or helical. 8 Nanofibers have been investigated in nanosized electronic, 9 mechanical 10 and medical fields. 11 One-dimensional nanostructures are also ubiquitous in biological systems, exemplified by collagen, axons, and keratin. There has been a rapid growth of interest in generating biomimetic fibrous structures with medical applications in terms of compatibility, degradability and cell-matrix interactions. 12  One interesting property that is frequently observed for nanofibers is gelation. The fibers form network structures, often through weak interfiber interactions, that can trap and immobilize solvent molecules, resulting in the formation of a gel. 13 Gels are interesting materials and already have a wide range of applications including biomedical applications, 14 drug delivery, 15 and catalysis, 16 depending on the nature of the materials forming the nanofibrils. They are also being explored for environmental sensors and have 2  been used to template sol-gel polycondensation of metal alkoxides such as tetraethyl orthosilicate (TEOS) and tetra-n-butyl titanate. 17 Given their interesting applications and properties, the synthesis and investigation of nanofibers with unique properties has become an attractive topic for researchers. 18  Numerous methods have been employed to manufacture nanofibers that span diverse size ranges. One way to produce fibrous nanostructures artificially is through the electrospinning technique. This process involves applying a high voltage between a metal collector plate (generally rotating) and the tip of a tiny needle that is ejecting a viscous polymer solution. 19 The polymer solution becomes charged in the electrical field, inducing electrostatic repulsion that creates a charged jet of solution erupting from the tip of the needle. While the jet is in air, the solution evaporates and the nanofibers deposit on the metal collector. 20 This method has many advantages – it allows good control over the morphology and porosity of the fibers, and it can be applied to diverse polymers and mixtures, permitting good control over composition. 21 The diameters of the electrospun fibers are in the range of nanometers to micrometers, but their lengths can extend to the kilometer scale. 22 These synthetic polymeric fibers possess good physical properties, including high specific surface area, flexibility in surface functionalities, and superior mechanical properties, which impart the nanofibers with excellent properties for use in biomedical engineering.21 Long hollow nanofibers can also be fabricated by electrospinning,  23  thus enhancing the specific surface area. Complementary to  electrospinning, supramolecular self-assembly has also received a great deal of attention for making nanofibers. Appropriately designed molecules and macromolecules act as the building units of the fibrillar aggregates, which then assemble into one-dimensional 3  nanostructures  through  noncovalent  interactions,  such  as  hydrogen-bonding,  intermolecular π-π stacking, electrostatic interaction/coordination chemistry, or the hydrophobic effect. 24 These molecule-based construction approaches to nanofibers provide a way to diversify the properties of the aggregates by tuning the functionalities of the building units. In recent years, fabrication of one-dimensional nanostructures has predominately involved intermolecular hydrogen-bonding and π-π stacking, or a combination of both non-covalent interactions, but significantly fewer with metal-ligand coordination interactions. Nevertheless, coordination chemistry offers a large and fascinating assortment of complexes with different geometries, and electronic and magnetic properties that can be incorporated into nanomaterials. Indeed, many elegant inorganic nanostructures with well-defined shapes, such as helicates, nanoboxes, catenanes and nanocages, 25 have been built using coordination chemistry, often relying on the bonding angles and geometry at the metal centers to dictate the final structure. Nanofibers constructed from extensive one-dimensional metal-ligand coordination interactions are an appealing class of materials because of their potential applications including catalysis, sensing, and gas storage. Their interesting electronic and magnetic properties also make them good candidates for nanoscale devices. 26 One can imagine using changes at the metal center (e.g., changes in coordination number, oxidation state, or electronic configuration) as a means to change the properties of the material.  In this chapter, the use of coordination chemistry to obtain nanofibers is described. In some cases, the assembly is formed through electrostatic interactions rather than extended metal-ligand interactions, but all contain metals and the metal is important to the assembly. Only examples where the fiber morphology has been imaged by a technique 4  such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), or atomic force microscopy (AFM) are included.  1.2 Nanofibers Constructed from Macrocyclic Units  Numerous types of macrocycles have been synthesized and studied, and they have played an important role in the development of the field of supramolecular chemistry. Some well-known groups of macrocycles, including crown ethers, aza-crowns, cryptands and cyclodextrins, are capable of coordinating to metal ions within their cavities, 27 which provide insight into supramolecular interactions and molecular recognition. The metal-containing  macrocycles  supramolecular behavior.  28  can  exhibit  intriguing  magnetic,  catalytic,  or  There are several reports of using intermolecular  hydrogen-bonding and π-π stacking as the driving forces of aggregation to form self-assembled fibrous superstructures from macrocycles. 29 Another approach to fabricate one-dimensional nanofibers is by using the metal-ligand coordination or electrostatic interactions. With macrocycle-based examples, most of these use the latter, where the charge of the metal complex is central to the assembly.  1.2.1 Metalloporphyrins and Metallophthalocyanines  Porphyrins are shape-persistent and conjugated macrocycles comprised of four pyrrole subunits that are interconnected by methine bridges. These heterocycles can be used as ligands to coordinate metals in their central cavities; metallated porphyrins play 5  important roles in nature, such as in heme and chlorophyll. The π-conjugated backbone, the metal center and the functional groups appended on the periphery render the metalloporphyrins the ability to self-assemble into a variety of supramolecular structures through non-covalent interactions. 30 Extensive efforts have been devoted to the research of multiporphyrin arrays due to their promising applications in molecular switching, electronic and photonic devices. 31 Intermolecular π-π stacking and hydrogen-bonding are commonly used to induce nanofiber structures; 32 these interactions can also combine with coordination chemistry and electrostatic interactions to construct beautiful fibrous networks  and  to  prepare  excellent  gelators.  33  One-dimensional  polymeric  metalloporphyrins synthesized solely by coordination chemistry and electrostatic interactions have been observed in solution and in the solid state. 34 Shelnutt and coworkers reported the formation of porphyrin nanotubes through the self-assembly of two oppositely charged porphyrins in aqueous solution. 35 The nanotubes can be used as photocatalysts to reduce metal complexes and deposit the metals onto the surfaces of the nanotubes, thus forming nanoscale metal-composite structures. This ionic self-assembly approach provides the ability to alter the molecular building subunits in order to control the structural and functional properties of the nanostructures. Shelnutt and co-workers also demonstrated a phase transfer ionic self-assembly approach to obtain bundles of porphyrin nanofibers employing water-soluble porphyrins (1, [MTPPS]4−) and water insoluble  oxo-antimony(V)  porphyrin  (2,  [SbOTPP]+)  (Figure  1.1)  in  an  aqueous/methylene chloride mixture. 36 The bundles of nanofibers are 70–140 nm wide and 1–2 μm long, with each individual fiber having a diameter of 20–40 nm (Figure 1.2). Photocatalytic studies showed that these porphyrin nanofiber bundles can reduce metal complexes and attain metal clusters (10–100 nm in diameter, depending on the metal 6  center of porphyrin 1) on the surface of the nanofibers. The photoactivity of these bundles directly takes advantage of the intrinsic properties of the inorganic building blocks and demonstrates that the preparation of porphyrin-metal composite nanostructures can lead to potential applications in electronics and photonics.  OO S O  O O S O  N  N II  -  M N  N  O S OO  N O N SbV N N  O S O O-  1, [MTPPS]4M = 2H, Cu, Ni, Ag, Zn  2, [SbOTPP]+  Figure 1.1. Chemical structures of porphyrins 1 and 2.  Figure 1.2. (a) TEM and (b) SEM images of the bundles of porphyrin nanofibers. Copyright Wiley-VCH Verlag GmbH and Co. KGaA. Reproduced with permission from reference 36. 7  Taking advantage of metal-ligand coordination interactions, chemists have produced one-dimensional polymeric metalloporphyrin aggregates. Shinkai and co-workers reported a porphyrin with eight pyridyl groups (3) that self-assembles into a coordination polymer (4) through palladium(II)-pyridine interactions with four cis-palladium(II) complexes (Scheme 1.1). 37 A light-scattering study of a chloroform solution of porphyrin polymer 4 revealed that the aggregate is assembled in solution, but the polymeric structure was not observed in polar solvents (e.g., in a mixture of 7:3 (v/v) chloroform/methanol). From these results, the authors concluded that the stability of the palladium(II)-pyridine coordination bonds is influenced by the solvent, which directly affects the occurrence of the porphyrin polymeric structure and allows one to use solvent to control the assembly. When a chloroform solution of polymer 4 was dried and viewed under TEM, long nanofibers with diameters of ca. 10 nm were observed (Figure 1.3). It is noteworthy that the theoretical structure of porphyrin polymer 4 shown in Scheme 1.1 but the polymeric structure was not observed in polar solvents (e.g., in a mixture of 7:3 (v/v) chloroform/methanol). From these results, the authors concluded that the stability of the palladium(II)-pyridine coordination bonds is influenced by the solvent, which directly affects the occurrence of the porphyrin polymeric structure and allows one to use solvent to control the assembly. When a chloroform solution of polymer 4 was dried and viewed under TEM, long nanofibers with diameters of ca. 10 nm were observed (Figure 1.3). It is noteworthy that the theoretical structure of porphyrin polymer 4 shown in Scheme 1.1 possesses many large cavities. As a result of these cavities, the polymer can bind guest molecules such as 4,4′-trimethylenedipyridine, in which each of the two pyridyl units coordinates to the axial position of different zinc(II) centers and bridge two porphyrin planes. The inclusion of various guest molecules in the cavities of the polymeric structure, 8  where they can interact with the metal and the π-conjugated system, can potentially tune the properties of the porphyrin nanofibers.  Scheme 1.1. Synthesis of porphyrin coordination polymer 4.  9  Figure 1.3. TEM image of the porphyrin nanofibers. Reproduced with permission from reference 37. Copyright 2001 The Chemical Society of Japan.  Phthalocyanines are chemical cousins of porphyrins – related, but different – that have received attention due to their optical, catalytic, electronic, photonic, and chemical sensing properties. 38 Phthalocyanines are generally easier to prepare than porphyrins, and this has helped them to flourish. Like porphyrins, phthalocyanines are capable of assembling into one-dimensional supramolecular structures through non-covalent intermolecular interactions. Many polymeric superstructures have been prepared and analyzed in solution. Tung and co-workers reported the preparation of zinc(II)-containing phthalocyanines with four aryloxy substituents (5a and 5b, Figure 1.4). 39 In solution, J-aggregates were observed by UV-vis spectroscopy in non-coordinating solvents and this was supported by the red-shifted and split Q-bands when compared to the absorption spectra of monomeric zinc(II)-containing phthalocyanines in coordinating solvents. The aggregation of 5a and 5b in non-coordinating solvents was also confirmed by matrix-assisted  laser  desorption  ionization  time-of-flight  (MALDI-TOF)  mass  spectrometry. A mass spectrum of 5a prepared from a chloroform solution showed eight distinct peaks corresponding to monomer and oligomers (up to octamer), consistent with aggregation. In addition, the aggregates were studied with TEM, imaging samples of 5a deposited from chloroform. The TEM micrograph, shown in Figure 1.5a, depicts a 10  two-dimensional network structure constructed from nanofibers about 50nm in diameter. When the sample for TEM was prepared at a lower concentration, nanoparticles were observed along with the network (Figure 1.5b). The authors proposed that the aggregation of these complexes is mediated by Zn···O interactions, where the ether oxygen in the aryloxy group of one phthalocyanine molecule can coordinate to the zinc(II) center of the neighboring phthalocyanine molecule. This is substantiated by control experiments that disrupted the aggregation by coordinating solvents. For example, the addition of coordinating solvent during the TEM sample preparation disrupted the Zn···O interactions and, as a result, no network structure was detected.  Figure 1.4. Chemical structure of phthalocyanines 5a and 5b.  11  Figure 1.5. TEM images of samples of 5a prepared from chloroform at concentrations of (a) 1 x 10-5 M and (b) 1 x 10-6 M. Reproduced with permission from reference 39. Copyright 2007 American Chemical Society.  Würthner and co-workers took advantage of the Zn···O interactions, along with intermolecular hydrogen-bonding and π-π interactions, to obtain tubular J-aggregates from a series of zinc(II) chlorins (one of the porphyrin analogues) in aqueous and organic media. 40 These self-assembled zinc(II) chlorin structures that mimic the supramolecular organization of natural light harvesting systems (e.g., bacteriochlorophylls) form well-defined short nanorods (lengths of ca. 300 nm and heights of ca. 6 nm) rather than extended nanofibers observed in the other structures discussed.  Although most fibers have been constructed from aggregates that form in solution, fabrication of supramolecular assemblies using a liquid-liquid interface has drawn some attention. magnesium(II)-containing phthalocyanines with eight chiral thioether substituents on the periphery (MgPc(SEtPh)8, 6) were synthesized by Watarai and co-workers (Figure 1.6). 41 These phthalocyanines can bind palladium(II) ions to their peripheral sulfur atoms and exhibit two different modes of aggregation in toluene and at the toluene/water interface. When PdCl2 was introduced to MgPc(SEtPh)8 in toluene, two 12  phthalocyanine molecules stack into an H-type dimer in a twisted fashion with four palladium(II) centers acting as the bridges between the phthalocyanine planes. These twisted H-type dimers of (R)- and (S)-MgPc(SEtPh)8-Pd(II) complexes could be detected by blue-shifted Q-bands in UV-vis absorption spectra and Cotton effects in circular dichroism (CD). In contrast to the twisted dimers obtained in toluene, one-dimensional helical J-aggregation was observed when MgPc(SEtPh)8 was combined with PdCl2 at the toluene/water interface. UV-vis spectra of the MgPc(SEtPh)8-Pd(II) complexes showed that the Q-bands were red-shifted and CD spectra displayed Cotton effects for both complexes. These absorption and CD spectral data indicated that the interfacial J-aggregates of (R)- and (S)-MgPc(SEtPh)8-Pd(II) complexes are oriented in left-handed and right-handed helical arrangements, respectively. The models of the helical J-aggregates are depicted in Figure 1.7a. Field emission (FE) SEM images of the dried sample of palladium(II)-induced supramolecular structures revealed fibrous networks (Figures 1.7b,c) in which the individual fibers are ca. 80–120 nm in width and over 500 nm in length. Moreover, twisted fibers could be seen by FE-SEM (Figure 1.7c), supporting the CD spectral data showing helical arrangements of the interfacial J-aggregates. Watarai and co-workers also reported the toluene/water interfacial method to fabricate nanorods and nanoribbons that are facilitated by other thioether-derivatized magnesium(II)-containing phthalocyanines and palladium(II) complexes.  42  It is  noteworthy that the self-assembled superstructure can be controlled by combining the building units in a single liquid medium or at the interface of two immiscible liquids.  13  Figure 1.6. Chemical structures of MgPc(SEtPh)8 complexes 6a–6c.  Figure 1.7. (a) Schematic representation of the helical arrangement of the interfacial J-aggregate of MgPc(SEtPh)8-Pd(II) polymeric structure (MgPc(SEtPh)8 = squares, PdCl2 = spheres). FE-SEM images of the interfacial aggregate of (b) (R)-MgPc(SEtPh)8-Pd(II) and (c) (S)-MgPc(SEtPh)8-Pd(II) complexes. Twisted fibers can be clearly seen in (c). Reproduced with permission from reference 41. Copyright 2006 American Chemical Society.  14  1.2.2. Ion-induced Self-assembly  Macrocycles with large interior pores and appropriate functionality are anticipated to accommodate one or more guest molecules. Crown ethers, for example, are well-known to selectively bind cations to form metal complexes. Occasionally, the inclusion of guest metal ions in a macrocycle can lead to the formation of supramolecular architectures. Lehn and co-workers obtained nanofibers from macrocycle 7 (Figure 1.8) through K+ ion-induced assembly. 43  The central cavity of macrocycle 7, which has three  1,8-naphthyridine groups with the lone pairs on the nitrogen atoms directed inwards, resembles that of an aza-crown and thus was expected to bind K+ ions in solution (Figure 1.9a). Upon addition of potassium picrate to macrocycle 7 in chloroform-d1/methanol-d4, the authors detected aggregation by 1H NMR spectroscopy through broadening and shielding of the proton signals. The solid-state structure of the assembly was investigated by a TEM study of a dried sample of macrocycle 7 with K+ ions. When deposited from a chloroform/nitromethane mixture, fibers about 50 nm in diameter and microns in length were observed (Figure 1.9b). This aggregation approach promoted by alkali metal ions can also be observed in other macrocyclic systems.24f,44  15  R  N  N  N  N  N  N N  N N  N  N  R  N R  7a R = n-C4H9 7b R = OC12H25  Figure 1.8. Chemical structure of macrocycle 7.  Figure 1.9. (a) Schematic representation of the presumed aggregation process of macrocycle 7 with K+ ions. (b) TEM image of macrocycle 7b with K+ prepared in chloroform/nitromethane. Reproduced with permission from reference 43. Copyright 2008 American Chemical Society.  In nature, one can find many exquisite examples of self-assembly to inspire chemists in designing complex macromolecular assemblies and bio-inorganic composite materials. Biomolecules are often used utilized as constituents for studying biomimetic supramolecular assembly, and their organization can be facilitated by alkali cations. For 16  instance, guanosine, a nucleoside comprising guanine attached to a ribose ring, can associate into macrocyclic tetramers (G-quartets) through hydrogen-bonding in the presence of alkali metal ions such as Na+ and K+. The G-quartets can further self-assemble into columns with the cations being sandwiched between the layers of G-quartets.24f,44b, 45 Davis and co-workers reported the synthesis of calix[4]arene appended with four guanosine substituents and took advantage of the tendency of the ion-assisted self-assembly of guanosine in which tubular structures were obtained upon the addition of NaBPh4. 46 The Na+ ions are located at the inner core of the cation-filled channels and the nanotubes could be seen by TEM. However, it was the intermolecular hydrogen-bonding of two guanosine units of one calix[4]arene molecule with two of the neighboring guanosine units to form the G-quartets that led to the tubular aggregation. Rowan and coworkers reported the formation of hydrogels from a mixture of guanosines 8 and 9 (Figure 1.10) in aqueous potassium chloride. 47 The G-quartets generated in this case would be random hydrogen-bonding combinations between the two guanosines. Guanosine 8 can gelatinize in the presence of sodium or ammonium salts, but the resulting hydrogel showed poor stability (collapse of gel occurred after a short period of time at room temperature). 48 It was found that the introduction of hydrophobic non-gelling guanosine 9 to guanosine 8 increased the stability of the hydrogel due to the hydrophobic groups of guanosine 9 promoting cross-linking between the columnar stacks. In addition, the physical appearance and the stability of the gel can be tuned by varying the ratio of the two guanosines (guanosine 8/guanosine 9) in the gelation process (Figures 1.11a,b). Based upon the stability of the hydrogels, the ratios in the range of 60/40 to 40/60 of guanosine 8/guanosine 9 are the most effective combinations to prevent the gels from collapsing (even after a year at room temperature). AFM studies were performed on 17  the dried 60/40 and 40/60 gel samples in order to characterize the assembled networks. The micrographs showed nanofibers in both gel samples, but the morphology differs slightly with respect to the ratio of the two guanosine units (Figures 1.11c,d). The fibers of the 40/60 gel are shorter and wider than those of the 60/40 sample. The increase in fiber width is ascribed to more cross-linking between the fibrillar guanosine stacks driven by the hydrophobic effect that was enhanced by the addition of guanosine 9. In addition, the length of the fibers decreased with increasing guanosine 9 content because the stacking of the guanosine units was disrupted by the acetyl groups of guanosine 9. Guanine-rich DNA segments have also been shown to assemble into extended structures with embedded ion channels through alkali- and alkaline-earth metal ion assembly. 49 This research in biological self-assembly may help to design new biosensors, and to improve our understanding of ion transport in nature.  H O N HO O  N  N  NH NH2  N  N H  N  NH  O  N  N  NH2  OH  8  OAc  OAc  R  N N  H NH  H N O  N  H N  9 N  N O  O N  N  N  M+  H  HN H  OH  N  O N  AcO N  R  O  R  H N  N H  N  R  H  G-quartet  Figure 1.10. Chemical structures of guanosines 8 and 9, and a G-quartet.  18  Figure 1.11. Visual appearance of the hydrogels obtained from guanosine 8 and guanosine 9 in aqueous potassium chloride solution (a) 15 min and (b) 36 h after sample preparations. The ratios are listed as guanosine 8/guanosine 9. (c,d) AFM images of the 60/40 and 40/60 gels, respectively. Reproduced with permission from reference 47. Copyright 2009 American Chemical Society.  1.3. Nanofibers obtained from Coordination Polymers  Supramolecular  self-assembly  of  molecules  and  macromolecules  into  one-dimensional polymeric structures through coordination chemistry or electrostatic interactions has been a quest for many researchers. The coordination polymers are reversible aggregates that can break and reconnect during reactions, facilitating self-assembly. The use of the concept of extended metal-ligand interaction to construct fibrous nanostructures provides a way to diversify the properties of the assemblies by tailoring the functionalities of the organic ligands and varying the choice of metal centers. Nanofibers have also been imaged in some metal-containing gels. 50 There have been several reports of generating fibrous materials and networks with coordination polymers, and examples of these will be discussed later in this section.  19  1.3.1. Metal-ligand Coordination  Nanofibers constructed from metal ions and organic bridging ligands into coordination polymers have been research targets of interest because they can be simple to synthesize, but offer plentiful opportunities for structural variation and potential access to useful properties. For instance, Loh and co-workers designed and obtained a one-dimensional nanostructured light-harvesting antenna that can transform UV to red radiation. 51 The coordination-assisted self-assembly of the nanostructure involves the strong affinity between the two carboxylate groups of π-conjugated donor 10 (Figure 1.12) and zinc(II) ions in the presence of acceptor 11 (Figure 1.13). TEM and SEM studies of the assembled structure showed that nanofibers were obtained (Figures 13a,b, respectively) and they have diameters of 20–30 nm and lengths of up to several microns. The metal-ligand interactions of donor 10 and zinc(II) ions, accompanied by two additional acetate groups, gave negatively charged one-dimensional chains that underwent side-by-side packing through cationic acceptor 11. This assembly was further strengthened by the π-π interactions and hydrophobic effect perpendicular to the chain elongation, leading to the formation of the fibrous structures (Figure 1.13c). Absorption and emission analysis revealed red emission when a sample of the coordination aggregate was excited at 370 nm (optimal excitation for donor 10), which suggested effective energy transfer to the acceptor, illustrating the light-harvesting antenna effect in the nanofibers.  20  H13C6  C6H13  H13C6  C6H13  H13C6  C6H13  HOOC  COOH  10 N I  N  11  Figure 1.12. Chemical structures of π-conjugated donor 10 and acceptor 11.  Figure 1.13. (a) TEM and (b) SEM images of the nanofibers. (c) Schematic representation of the coordination-assisted self-assembly mechanism. Reproduced with permission from reference 51. Copyright 2009 American Chemical Society.  Oh and co-workers took advantage of the strong affinity of carboxylate groups to zinc (II) ions to create a coordination polymer that could assemble into nanofibers and  21  further  transform  into  nanocubes.  52  Salphen  11  (salphen  =  N,N′-bis(salicylidene)-o-phenylenediamine) was first synthesized and then combined with two equivalents of Zn(OAc)2 in a 1:2 mixture of dimethylsulfoxide (DMSO) and N,N-dimethylformamide (DMF). One equivalent of zinc(II) ion was coordinated by the salphen N2O2 pocket resulting in a zinc(II) salphen complex, which was then linked with other complexes by the second equivalent of zinc(II) ion into a coordination polymer (12) (Scheme 1.2). The supramolecular structure of the zinc(II) salphen coordination polymer was characterized by SEM. An interesting revelation of the SEM images is that the coordination polymers organized themselves into nanowires that are ca. 40 nm in diameter and ca. 600 nm in length at an early stage of reaction (Figures 1.14a,b). The nanowires then slowly aggregate together into a cubic structure and eventually transform into uniform nanocubes (Figures 1.14c–h). When more nanowires were involved in the aggregation, bigger nanocubes were obtained. The formation of nanowires and nanocubes could be controlled by the reaction conditions, such as the reaction temperature, the ratio of DMSO to DMF, and the reaction time. By understanding these factors, the size and morphology of the coordination polymer aggregates with unique chemical and physical properties can be controlled.  22  Scheme 1.2. Salphen 11 combines with zinc(II) to form nanowires and nanocubes, with the chemical structure depicted by 12. Copyright Wiley-VCH Verlag GmbH and Co. KGaA. Reproduced with permission from reference 52.  Figure 1.14. (a–h) SEM images monitoring the transformation of nanowires into nanocubes. Copyright Wiley-VCH Verlag GmbH and Co. KGaA. Reproduced with permission from reference 52.  23  1.3.2. Static Coordination Polymer Gels  An appealing feature of nanofibers is that they are able to trap and immobilize solvent molecules within their fibrous networks’ interstitial spaces, and thus promote the formation of gels. Designing coordination polymer gelators has been of interest because the metal centers of the metallogels bestow upon them intriguing properties and applications. 53 For instance, Su and co-workers have synthesized a series of coordination polymer gels from different ratios of compound 13 (Figure 1.15) and Pd(COD)(NO3)2 (COD = cycloocta-1,5-diene) in a mixed methanol/chloroform solution (Figure 1.16a). 54 In addition to the metal-ligand coordination that extends through the gel, hydrogen-bonding between the amide groups and π-π stacking between the cores of the ligand molecules help to stabilize the metallogels. SEM analysis of the xerogels of the coordination polymers revealed that the morphology of the supramolecular structures depends on the reaction ratio of the metal and 13 (Figure 16b). Well-defined fibers with widths of ca. 30–50 nm were observed when Pd(COD)(NO3)2 and the tritopic ligand were combined in 1:1 ratio, whereas other ratios led to either spherical or porous structures (Figures 1.16c,d, respectively). The metallogels formed with palladium(II) were found to have catalytic activity in the Suzuki-Miyaura coupling reaction, even at 1 mmol% of coordination polymer. Among the gels tested in the catalytic study, the fibrous metallogel (1:1 metal/13) showed the highest catalytic activity in the coupling reaction. Furthermore, the fibrous networked gel can be recycled several times without significant reduction in its catalytic activity. It is clear that gels formed from metallofibers have excellent potential for catalytic applications.  24  Figure 1.15. Chemical structure of compound 13.  Figure 1.16. (a) Photograph of metallogels with metal/13 of 1:4 (left), 1:2 (middle) and 1:1 (right). SEM images of xerogels with (b) fibrous, (c) spherical, and (d) porous structures. Reproduced with permission from reference 54. Copyright 2009 American Chemical Society.  25  You and co-workers applied concepts of coordination chemistry to obtain helical non-racemic polymers from achiral monomers that can form gels even without the side chain functionality (e.g., hydroxyl groups or long aliphatic chains) usually necessary to stabilize the aggregates in the gel state. 55 The coordination polymers were derived from the self-assembly of silver(I) ions and the bent-shaped, achiral and ditopic imidazoles 14 and 15 (Figures 1.17 and 1.18a). They could gelatinize solvents including DMF, glycol, and mixtures of water and organic solvents (e.g., methanol, ethanol, acetonitrile, chloroform, methylene chloride and toluene). The metallogels were found to be stable for several months at room temperature and in acidic conditions. Nonetheless, the gelation of the helical coordination polymers is dependent on the counteranion of the silver(I) salts. For instance, AgNO3 and AgOSO2CF3 generate gels, while only precipitates formed with AgBF4 and AgSbF6. Investigations on the assembled structure of the coordination polymer gel generated from imidazole 14 and AgNO3 were performed by TEM, SEM and AFM (Figures 1.18b–e). TEM images showed that the nanofibers are cylindrical aggregates with diameters of ca. 9 nm and lengths up to several microns (Figure 1.18b). Closer inspection of the fibers with AFM revealed a helical structure with helical pitch of ca. 8 nm (Figure 1.18d). In addition, an SEM image of the xerogel showed a well-defined fibrous network structure (Figure 1.18e). The helicity of the nanofibers was further confirmed with CD. Cotton effects were observed in the CD spectra; the sign of the CD signals, however, varied with different batches of the gel prepared from the same materials. The CD data indicated that there is no control over the handedness of the helical non-racemic organization of the coordination polymers and nanofibers.  26  Figure 1.17. Chemical structures of bisimidazole 14 and bisbenzimidazole 15.  Figure 1.18. (a) Schematic representation of the formation of the helical coordination polymer gelators formed from 14 and 15. (b) TEM image of the dried gel (the sample was negatively stained with uranyl acetate solution). The inset is a magnified image of the marked area. (c) AFM (height trace, tapping mode) image of the dried gel on a mica surface. (d) A magnified AFM image of the marked area. (e) SEM image of the xerogel stained with gold. Reproduced with permission from reference 55. Copyright 2008 The Royal Society of Chemistry. 27  You and co-workers further expanded their investigation of coordination polymer gels in the absence of peripheral functionality, reporting the formation of a zinc(II)-containing metallogel formed upon irradiation with ultrasound.  56  The  coordination polymer was prepared by reacting Zn(OSO2CF3)2 with the simple organic bridging ligand 4,4′-bis(1-imidazolyl)biphenyl (bibp, 16, Figure 1.19). SEM of the self-assembled zinc(II) coordination polymer revealed sheet-like microparticles with uniform size and shape (Figure 1.20a). Single crystals of the zinc(II) complex, obtained by slow diffusion of dioxane into a DMSO solution of the coordination polymer, were analyzed by X-ray diffraction and the structure revealed that each zinc(II) center has tetrahedral coordination geometry, bound to four imidazole nitrogen atoms from four different bibp units (Figure 1.20b). The nitrogen on the other end of the coordinated bibp molecules bridges the neighboring zinc(II) centers, weaving a two-dimensional coordination network (Figure 1.20c). The sheet-like microparticles of the coordination polymer did not form a gel or dissolve in methanol; however, after the suspension was sonicated for a period of 1–3 min, an opaque white gel was generated (Figure 1.20d) and was found to be stable for months at room temperature. Electron microscopy was used to investigate the supramolecular structure of the gel, which should be different than the morphology before sonication (sheet-like microparticles) due to the newly discovered gelation phenomenon. High resolution TEM revealed the morphology of the metallogel to be uniform fibrous assemblies with diameters of ca. 3–4 nm and lengths up to several microns (Figure 1.20e). In addition, SEM of the xerogel showed a well-structured fibrous network in which the nanofibers are 50–200 nm in diameter (Figure 1.20f). The difference in diameters observed between the TEM and SEM images is ascribed to the aggregation of the nanofibers during the drying process. The morphological 28  transformation from sheet-like microparticles to nanofibers originated from the change in coordination environment of the zinc(II) centers before and after irradiation with ultrasound. Solid-state  13  C NMR spectroscopic experiments on the microparticles and  xerogel provided information about the geometrical change at the metal centers from the difference in chemical shifts of the aromatic carbon peaks in both samples. The sonication presumably facilitated the breaking and reorganizing of the coordination bonds and changed the geometry of the zinc(II) centers from tetrahedral in the sheet-like microparticles to see-saw geometry in the nanofibers (Figure 1.20g) that results in a fibrous network, giving a gel.  Figure 1.19. Chemical structure of 4,4′-bis(1-imidazolyl)biphenyl (bibp, 16).  29  Figure 1.20. (a) SEM image of the sheet-like microparticles formed from 16 before sonication. (b) Crystal structure of tetrahedral zinc(II) center with four bibp (16) units. (c) Two-dimensional coordination network. (d) A suspension before sonication (left) and an opaque white gel after sonication (right). (e) TEM image of the gel (negatively stained with uranyl acetate). (f) SEM image of the xerogel. (g) Metal coordination geometry is tetrahedral in the sheet-like microparticles and see-saw in the nanofibers. Reproduced with permission from reference 56. Copyright 2009 American Chemical Society.  Vittal and co-workers reported a hydrogel generated from Mg(CH3COO)2·4H2O and the basic aqueous solution of N-(7-hydroxyl-4-methyl-8-coumarinyl)alanine (17, Figure 1.21). 57 The carboxylate oxygen atoms of 17 coordinated to the neighboring metal center  30  to form the coordination polymer 18, shown in Figure 1.21. The coordination polymer gel is thixotropic and sensitive to pH. The gel liquefied upon shaking and reformed into a gel upon standing (Figure 1.22a). In addition, it turned into a clear solution at pH 2 because protonation of the ligand disrupted the structure, but this was reversible and a gel was formed when the pH was adjusted to 8. The morphology of the hydrogel was analyzed by electron microscopy. From the SEM and TEM micrographs of the xerogel, polymer 18 self-assembled into bundles of nanofibers and further organized into a well-defined network capable of trapping solvent molecules (Figures 1.22b,c). The fibers are several microns long and the diameters are 50–150 nm. Photophysical studies of the hydrogel showed that it exhibited strong blue emission with peak maximum at λ = 455 nm when excited at λ = 360 nm. The intensity of the fluorescence was enhanced significantly in the gel form compared to free ligand 17 and a solution of coordination polymer 18. Vittal and co-workers further reported a coordination polymer gel produced from linear bridging ligands and Ni(II) ion in an acidic medium. 58 An initial morphological study of the gel with SEM revealed no fibrous structure. The gel was then diluted to half the original concentration and homogenized by stirring. After that, it was subjected to electrospinning to generate bundles of nanofibers, and the fiber morphology was confirmed by SEM, TEM and AFM. The electrospun fibrous bundles are ca. 100 nm in diameter and centimeters in length, with individual fibers having a diameter of ca. 10 nm. It is noteworthy that the electrospun fibers exhibited strong photoemission in the visible and UV regions, and field emission with low turn-on fields for metal-coordinated nanofibers. 59  31  Me  Me O HO  O HN  HO  O  O O H2O Mg NH H2O O  Me  O  O  Me  O  O  Mg  17  18  Figure 1.21. Chemical structure of the free ligand 17 and schematic representation of the proposed coordination polymer 18.  Figure 1.22. (a) Photograph of ligand 17 in water (left) and hydrogel (right). (b) SEM and (c) TEM images of the xerogel of coordination polymer 18. Copyright Wiley-VCH Verlag GmbH and Co. KGaA. Reproduced with permission from reference 57.  1.3.3. Dynamic Coordination Polymer Gels One-dimensional assemblies of coordination complexes are attractive for their electronic, magnetic and optical properties. 60 However, solubility of the supramolecular assemblies has always been a challenge, and has limited the ways in which coordination polymers can be manipulated. Kimizuka and his co-workers have focused on this area of research and reported a series of coordination polymers with solubility promoted by incorporating lipophilic triazole bridging ligands into the polymeric main chains, or by 32  introducing lipid-like counteranions in the vicinity of the metal centers. Lipophilic cobalt(II) complexes 19 and 20, shown in Figure 1.23, were synthesized with ligands 4-hexadecyl-1,2,4-triazole (21) and 4-dodecyloxypropyl-1,2,4-triazole (22). 61 The long chains on these ligands are used to enhance the solubility of the complexes and the polymeric aggregates. When complexes 19 and 20 were dissolved in chloroform, blue gels were obtained at low concentrations (10 and 0.007 wt% for 19 and 20, respectively) as depicted in Figure 1.24a. The blue color, characteristic of cobalt(II) in a tetrahedral (Td) coordination environment, revealed the geometry at the metal center. The gels were studied by AFM, SEM and TEM (Figures 1.24c–f) to gain insight into the supramolecular organization. Complex 19 showed crystalline nano-aggregates with lengths of ca. 500–1500 nm and widths of 30–50nm (Figure 1.24e) by TEM. On the other hand, the AFM and TEM micrographs of complex 20 revealed fibrous networks in which the nanofibers are 5–30 nm in diameter. In addition, the xerogel of complex 20 displayed thicker fibers (ca. 100 nm in diameter) by SEM due to the aggregation of the nanofibers during the drying process. That complex 19 did not develop into a fibrous network is related to its lower gelation ability compared to complex 20. It is interesting to note that no fiber morphology was observed with either of the lipophilic ligands alone. Therefore, the fibrous nanostructure is attributed to the self-assembly of the cobalt(II) complexes in chloroform, and the cobalt centers adopted a Td geometry along the main chain (Figure 1.24g). A special feature of these gels is that they turn into pale pink solutions upon cooling (Figure 1.24b) and return to blue-colored gels upon heating. This heat-induced gelation is contrary to the behavior of conventional gels (i.e., gelation upon cooling and dissolution upon heating). The sol-to-gel transition is reversible with subsequent cooling and heating cycles. The pink color indicates that the cobalt(II) centers are in octahedral 33  (Oh)  coordination  environment  (Figure  1.24h)  and  the  reversible  geometric  transformation at cobalt was confirmed by UV-vis spectroscopy. The authors proposed that the coordination polymer with Oh metal centers in the solution state has a rod-like structure with the lipophilic chains aligned perpendicular to the main chain. However, no superstructures were observed by TEM. The gel transition is also toggled by the addition of long-chained alcohols including 1-dodecanol and 1,12-dodecanediol. 62 When either alcohol was added to a pink solution of complex 20 obtained at 0 oC, the solution turned blue within ca. 5 min and a gel formed within ca. 10 min. Again, the color change corresponded with a change in the geometry of the complex from Oh to Td, which was confirmed by UV-vis spectroscopy. TEM analysis of the gels showed networks of fibrous structures with widths of ca. 100 and 500nm for the samples prepared with 1-dodecanol (Figure 1.24i) and 1,12-dodecanediol (Figure 1.24j), respectively. Binding of the long chained alcohols to the surface of the coordination polymer through hydrogen-bonding to the anions (ROH· · ·Cl−) induces the transformation of the geometry to Td in order to fit the guest molecules, the long chains of ligand 21 and alcohol molecules aligning perpendicular to the polymer chain. These studies indicate that the coordination geometry at cobalt centers can be modified by changing the temperature and by binding guests, triggering a change of color and morphology.  Figure 1.23. Chemical stoichiometries of lipophilic cobalt(II) complexes 19 and 20, and ligands 21 and 22 34  Figure 1.24. Photographs of complex 20 in chloroform at (a) 25 ºC (blue gel) and (b) 0 ºC (pale pink solution). (c) AFM and (d) TEM images of complex 20. (e) TEM image of complex 19. (f) SEM image of the xerogel of complex 20. Schematic representations of (g) polymeric Td complex and (h) polymeric Oh complex. Reproduced with permission from reference 61. Copyright 2004 American Chemical Society. TEM images of complex 20 with (i) 1-dodecanol and (j) 1,12-dodecanediol. Reproduced with permission from reference 62. Copyright 2008 The Chemical Society of Japan.  Lipophilic, linear polymeric iron(II) triazole complex 23 containing octahedral metal centers was prepared with ligand 22 (Figure 1.25). 63 Polymer 29 (Figures 1.26a,b) exhibits spin-crossover behavior between low spin (LS) and high spin (HS), and each spin state of the iron(II) triazole complexes has a characteristic color (purple = LS and yellow or colorless = HS). The spin-crossover characteristics are usually affected by the 35  type of substituent on the bridging ligands and the counteranions incorporated. Complex 23, a purple solid, gave a pale yellow gel at room temperature in chloroform (Figure 1.26c). The color indicated that iron(II) centers changed from LS state to HS state after gelation. This is attributed to the elongation of the Fe-N coordination bonds in solution, weakening the ligand field strength and thus favoring the HS state. The supramolecular structure of the gel was investigated by TEM and nanofiber superstructures with widths of 3–5 nm could be observed (Figure 1.26c). Similarly, the coordination gel obtained with complex 20 turned into a yellow solution upon cooling to 5 oC. When the yellow chloroform solution of complex 23 was cast onto a solid substrate and dried into a transparent film, the color changed to purple upon solvent evaporation due to spin crossover to the LS state (Figure 1.26d). As the purple-colored film was heated, it returned to a yellow color at 80 oC (Figure 1.26e). This reversible, temperature-dependent spin crossover was monitored by UV-vis spectroscopy. In addition, the temperature of the spin crossover for complex 23 is affected by the presence of long-chained alcohols such as 1-dodecanol and 1-tetradecanol, which are able to hydrogen-bond to the chloride counteranions of the iron(II) complex (Figure 1.26f). When chloroform solutions of complex 23 combined with equimolar alcohol were cast as films, UV-vis spectroscopic studies showed that the LS-to-HS transition temperatures were lowered (55 and 68 oC for 1-dodecanol and 1-tetradecanol doping, respectively) compared to that before alcohol doping (80 oC), thus indicating that the LS state was destabilized by the binding of guest alcohol molecules.  36  . Figure 1.25. Chemical stoichiometry of lipophilic iron(II) complex 23.  Figure 1.26. Schematic representations of (a,b) the lipophilic polymeric iron(II) complex 23. (c) The yellow gel (20 ºC in chloroform) and TEM image of complex 23. Photographs of cast films at (d) 20 and (e) 80 ºC. (f) Schematic representation of the long-chained alcohols hydrogen-bonded to the chloride counteranions. Copyright 2006; Reproduced with permission of John Wiley & Sons, Inc from reference 63.  Iron(II) triazole complexes 24 and 25 were developed with ligand 22 and chromophoric counteranions 9,10-dimethoxyanthracene-2-sulfonate (Anth-SO3-) and 1-pyrenesulfonate (Py-SO3-) (Figure 1.27), 64 and their fluorescence properties were studied. The anionic chromophores are located in the vicinity of iron centers along the  37  coordination polymeric main chain. Toluene solutions of complexes 24 and 25 prepared at different temperatures, where they exhibited different spin states, were dried and then the solids analyzed by AFM. Fibrous nanostructures with widths of 20–30 nm and heights of ca. 1.5 nm were observed for complexes 24 and 25 in the LS state (10 and 4 oC, respectively) (Figures 1.28a,c), but only irregular structures or dot-like aggregates could be seen in the HS state (40 and 45 oC, respectively) (Figure 1.28b,d). This change in the morphology of the self-assembled structures from LS to HS (nanofibers to dot-like structure) upon heating gradually diminished the fluorescence intensities of the counteranions. Therefore, the fluorescence of the chromophores was related to the spin state of the metal center and the morphology of the coordination aggregate.  Figure 1.27. Chemical stoichiometries of lipophilic iron(II) complexes 24 and 25.  38  Figure 1.28. AFM images of complex 24 in the (a) LS and (b) HS states, and complex 25 in the (c) LS and (d) HS states. Reproduced with permission from reference 64. Copyright 2008 The Chemical Society of Japan.  The morphology of the coordination polymer can be regulated by solvent and external stimuli such as temperature and irradiation. For instance, the bridging ligand was modified by incorporating an azobenzene chromophore, which can undergo photoisomerization upon irradiation, within the lipophilic substituent of triazole (26, Figure 1.29). The new linear iron(II) triazole complex (27) formed from this ligand has iron centers in Oh coordination environments (Figure 1.30a). 65 A structural study was performed on complex 27 prepared in chloroform and a fibrous morphology was observed by AFM (Figure 1.30b). The nanofibers were ca. 6.9 nm in diameter and 10–100 nm in length. No gelation occurred for complex 27 in chloroform, but when chlorocyclohexane was used as the solvent, a yellow-colored coordination polymer gel formed in 6–24 h (Figure 1.30c). AFM of the sample prepared in chlorocyclohexane showed oriented arrays of aggregates with lengths over 400 nm and heights of ca. 1 nm 39  (Figure 1.30h). The morphology is different than that observed from the chloroform sample. Moreover, the average distance between the linear structures in Figure 1.30h is ca. 6 nm, which is smaller by 1 nm compared to the nanofibers in Figure 1.30b. SEM of the xerogel of complex 27 showed ultra-thin nanosheets with a thickness of ca. 10 nm (Figure 1.30g). The formation of the nanosheets was derived from the two-dimensional alignment of the linear aggregates, which can be rationalized by the height measured by AFM, in agreement with the thickness of the nanosheets observed by SEM. The trans-to-cis photoisomerization of the azobenzene units was studied by irradiating gels of complex 27 with UV light at 365 nm. Upon irradiation, the yellow gel liquefied into an orange solution (Figure 1.30d). The coordination sphere of the metal in complex 27 remained unchanged after isomerization of the azobenzene, but the gel was liquefied as the bent-shaped cis-azobenzene disrupted the packing of the lipophilic substituents (Figure 1.30a). AFM of the UV irradiated sample revealed a fiber morphology (Figure 1.30i) similar to that in Figure 1.30b (chloroform sample). An interesting feature of the orange solution is that upon irradiating with visible light, cis-to-trans photoisomerization of the azobenzene units took place and the color of the solution returned to yellow and a yellow-colored gel formed after sitting in the dark for 20 min. The gel-to-sol transition induced by UV and visible light, triggered by the cis–trans isomerization, is reversible and the cycle could be repeated multiple times.  40  H25C12O  N  N  O  O  N  N  N  26 H25C12O  N  N  O  27  O  N  N  Fe(BF4)2  N 3  Figure 1.29. Chemical structure of ligand 26 and stoichiometry lipophilic iron(II) complex 27.  Figure 1.30. (a) Schematic representation of lipophilic polymeric iron(II) complex 27. (b) AFM of the sample prepared in chloroform. (c–f) Photographs of complex 27 in chlorocyclohexane at room temperature: (c) before irradiation, (d) after irradiation with UV light (365 nm), (e) after irradiation with visible light (546 nm), and (f) after storage in the dark for 25 min. (g) SEM of the xerogel. (h) AFM of the sample prepared in chlorocyclohexane (h) before and (i) 2 min after irradiation with UV light (365 nm). Reproduced with permission from reference 65. Copyright 2006 The Royal Society of Chemistry.  41  The iron centers in most iron(II) triazole complexes tend to exhibit the LS state in the solid or gel form, and HS state in solution. This is closely related to the bonding distance between iron and the bridging ligand, which is lengthened in solution and results in the destabilization of the LS state. Iron(II) triazole complexes 28 and 29 with lipophilic counteranions were synthesized and both have a purple color at room temperature when they are dissolved in toluene, indicating that the complexes remain in the LS configuration in solution (Figure 1.31). 66 As the temperature of the solution was raised, spin crossover occurred; this LS-HS transition is reversible with subsequent cooling and heating cycles (Figure 1.32a). The unusual LS state in toluene was ascribed to the solvophobic iron(II) triazole complexes minimizing contact with the non-polar solvent molecules by shrinking the Fe-N bonds, thereby strengthening the ligand field and leading to the stabilization of the LS state. AFM images of complexes 28 and 29 were obtained to investigate the superstructures of the complexes in different spin states (Figures 1.32b–e). Nanofibers with widths of 20–30 nm and heights of ca. 7 nm were observed for the LS state (Figures 1.32b,d) while the HS state gave only fragmented structures or dots (Figures 1.32c,e). Since the coordination number at the metal centers should not change during spin crossover, the change in spin state with respect to temperature apparently involves the fragmentation of the fibrous nanostructures (breaking of the coordination bonds). Thus, the transition between LS and HS is regulated by supramolecular self-assembly of the iron complex.  42  Figure 1.31. Chemical stoichiometries of lipophilic iron(II) complexes 28 and 29.  Figure 1.32. (a) Schematic representation of the reversible LS-HS transition with cooling and heating cycles. AFM images of complex 28 in the (b) LS and (c) HS states, and complex 29 in the (d) LS and (e) HS states. Reproduced with permission from reference 66. Copyright 2008 American Chemical Society.  Kimizuka and co-workers have also prepared a family of one-dimensional halogen-bridged, mixed-valence platinum complexes from [Pt(en)2][PtCl2(en)2](ClO4)4 43  with  lipid  counteranions  (30–37,  Figure  1.33).  67  These  linear  complexes  [Pt(en)2][PtCl2(en)2](30–37)4 are composed of [Pt(II)(en)2] and [Pt(IV)Cl2(en)2] that are bridged by chloride, and the charge of each of the platinum centers is balanced by two lipid anions (Figure 1.34). [Pt(en)2][PtCl2(en)2](30–37)4 have intense colors that originate from the intervalence charge transfer (CT) absorption of the chloro-bridged platinum(II)/platinum(IV) along the coordination polymer backbones. Different colors could be obtained by changing the CT absorption. There are three factors that affect the CT absorption of the mixed-valence platinum complexes: the nature of the counteranions, the solvent, and the temperature. As already noted, those three factors can also influence the supramolecular self-assembled structures of coordination polymers. The incorporated counteranions promoted solubility in organic solvents, but their sizes affect the distance between the platinum(II) and platinum(IV) centers and, as a result, induced a change in the CT absorption. In general, bulkier counteranions (e.g., 33, 34) increase the intrachain Pt(II)-Pt(IV) distance and red-shift the CT absorption with respect to the reference complex [Pt(en)2][PtCl2(en)2](ClO4)4, while smaller anions decrease the distance and show a blue-shifted band (e.g., with 35).67a In addition, the complexes are strongly solvatochromic. For example, [Pt(en)2][PtCl2(en)2](37)4, an orange solid, gave a red solution when dissolved in methylene chloride, while an orange solution was obtained in chloroform.67c  44  Figure 1.33. Chemical structures of lipid counteranions 30–37.  Figure 1.34. Schematic representation of polymeric platinum complexes with lipid counteranions. Reproduced with permission from reference 67b. Copyright 1998 The Chemical Society of Japan.  The lipid counteranions and solvents not only influence the color of the platinum complexes, but also the morphology of the superstructures of the coordination polymers. Complexes of [Pt(en)2][PtCl2(en)2](30–37)4 exhibited different morphologies when imaged by TEM (Figures 1.35a–g). Since all of the complexes contain the same  45  chloro-bridged platinum(II)/platinum(IV) backbone, the morphology difference must be derived from the counteranions and solvents. Nanofibers with widths of 20–100 nm and lengths of over 20 microns were observed for [Pt(en)2][PtCl2(en)2](37)4 in chloroform (Figure 1.35f), but only nanorods, nanocrystals or tape-like structures were obtained with other counteranions or samples prepared in different solvents (Figures 1.35a–e,g). Another phenomenon of the linear mixed-valence complexes is that the intense color tends to fade out and eventually disappear as the temperature of the solution increases. The absence of color is a sign that the complexes [Pt(en)2][PtCl2(en)2](30–37)4 have dissociated into [Pt(en)2](30–37)2 and [PtCl2(en)2](30–37)2 at elevated temperatures, eradicating the CT band. Different solvents and counteranions rendered different thermal stability to the linear platinum complexes, and the dissociation of the coordination polymers at elevated temperatures resulted in different morphologies observed by TEM. For example, [Pt(en)2][PtCl2(en)2](34)4 gave a tape-like morphology before heating (Figure 1.35b), but crystalline aggregates with widths of 50–200 nm and lengths of 400–550 nm were observed upon heating to 60 oC (Figure 1.35h). After the sample cooled back to room temperature, fibrous nanostructures with a minimum width of 18 nm and lengths of 700–1700 nm were obtained (Figure 1.35i). The formation of the nanofibers is ascribed to the self-assembly of the dissociated components in solution (Figure 1.35j). 67d It is noteworthy that as the samples cooled, the intense color from the CT band returned. However, for [Pt(en)2][PtCl2(en)2](30)4, only globular aggregates with diameters of 100–300 nm were observed after cooling the sample from 60 to 25 oC (Figure 1.35j).67a The linear platinum coordination polymers dissociated into [Pt(en)2](30–37)2  and  [PtCl2(en)2](30–37)2  at  elevated  temperatures,  but  the  one-dimensional complexes are reassembled upon cooling (Figure 1.35k). 46  Figure 1.35. TEM images of the mixed-valence platinum complexes with lipid counteranions (a) 30, (b) 32, (c) 34, (d) 35, (e) 36, (f) 37 in chloroform, (g) 37 in methylene chloride, (h) 34 at 60 ºC, (i) 34 after cooling from 60 ºC to room temperature, and (j) 30 after cooling from 60 ºC to room temperature, respectively. (k) Schematic representation of the reversible dissociation/re-assembly process. (a,c–e,h–k) Reproduced with permission from reference 67a. Copyright 2000 American Chemical Society. (b) Reproduced with permission from reference 67b. Copyright 1998 The Chemical Society of Japan. (f,g) Reproduced with permission from reference 67c. Copyright 2002 The Chemical Society of Japan. 47  One-dimensional  halogen-bridged,  mixed-valence  palladium  complexes  ([Pd(en)2][PdCl2(en)2](34)4) and heterometallic complexes ([Pd(en)2][PtCl2(en)2](34)4 and [Ni(en)2][PtCl2(en)2](34)4) have also been reported. 68 These complexes had similar behavior to the platinum complexes, and their colors and morphologies can be influenced by external stimuli.  Linear lipophilic [Pt(en)2][PtCl2(en)2](38)4 (Figure 1.36) was prepared by another route. Addition of HAuCl4 to [Pt(en)2](38)2 (colorless) in methylene chloride yielded the intensely colored chloro-bridged mixed-valence complex. 69 In this polymeric complex, the intensity of the CT absorption depends on the amount of tetrachloroaurate(III) added to the reaction. The maximum intensity was obtained at 3:1 [Pt(en)2](38)2/HAuCl4. In addition, the ratio also affected the morphology of [Pt(en)2][PtCl2(en)2](38)4 when observed by TEM (Figure 1.37). Before the addition of gold(III) ion, [Pt(en)2](38)2 only gave irregular microcrystalline aggregates (Figure 1.37a). Upon adding HAuCl4, nanowires were obtained (Figures 1.37b–d), and the most developed nanowires (lengths of 30–100 microns and widths of ca. 670 nm) were observed from the sample of 3:1 [Pt(en)2](38)2/HAuCl4 (Figure 1.37c). The analogous bromo-bridged structure was prepared with AuBr3 and exhibited similar behavior.  Figure 1.36. Chemical structure of lipid counteranion 38. 48  Figure 1.37. TEM images of the samples prepared in methylene chloride: (a) [Pt(en)2](38)2, (b) 6:1, (c) 3:1, and (d) 2:1 of [Pt(en)2](38)2/HAuCl4. Reproduced with permission from reference 69. Copyright 2005 The Chemical Society of Japan.  Kimizuka and co-workers have also prepared lipophilic mixed-valence platinum complexes  [Pt(en)2][PtCl2(en)2](39)4  (Figure  1.38)  that  self-assemble  into  two-dimensional honeycombs templated by water droplets condensed from moisture. 70 The TEM image of a sample prepared at 0 oC showed that well-constructed honeycombs could be observed in a wide area (Figure 1.39a). The walls of the honeycombs are composed of the linear coordination polymer [Pt(en)2][PtCl2(en)2](39)4. A magnified TEM image revealed that the cavities of the honeycombs were filled with nanofibers that are ca. 20 nm in width (Figure 1.39b). The formation of the honeycomb structure is templated by water droplets that condense on the evaporating methylene chloride solution during the sample preparation. A honeycomb structure with improved order was observed for a sample prepared at 21 oC (Figure 1.39c). Since solution studies showed that the  49  coordination polymer dissociated into [Pt(en)2](39)2 and [PtCl2(en)2](39)2 at 21 oC, the formation of honeycombs must derive from the re-polymerization of those two components into the linear mixed-valence chains and self-assembly into the supramolecular structure (Figure 1.39e). SEM images of the honeycombs clearly showed that the nanostructures are double-layered (Figure 1.39d) and the two layers of honeycomb are connected by vertical pillars with heights of ca. 320–370 nm at the corners of the hexagons. The frames (walls and pillars) of the double-layered honeycomb structure are constructed from the hierarchical self-assembly of the lipophilic mixed-valence coordination polymer [Pt(en)2][PtCl2(en)2](39)4 (Figure 1.39e).  Figure 1.38. Chemical structure of lipid counteranion 39.  50  Figure 1.39. (a,b) TEM images of [Pt(en)2][PtCl2(en)2](39)4 prepared at 0 ºC. (c) TEM and (d) SEM images of the sample prepared at 21 ºC. Reproduced with permission from reference 70. Copyright 2002 National Academy of Sciences, U.S.A..  51  1.4 Goals and Scope of This Thesis  Our research group’s interests have been based heavily on applying Schiff-base base chemistry to construct macrocycles and metallated salphen complexes, which can then be used as the building blocks to construct one-dimensional supramolecular self-assembled materials through a molecule-based bottom-up approach. Schiff-base chemistry involves the condensation between an aldehyde and an amino group to form an imine moiety. Due to the robustness and reversibility of Schiff-base condensation, numerous supramolecular chemists have employed this chemistry to synthesize macrocycles. 71 In particular, we have designed our target Schiff-base macrocycles (40–42) with salphen moieties, which give the macrocycles chelating sites for transition metals, and a central pore that resembles crown-ether for binding alkali metal and ammonium ions. Since there are examples of Schiff-base metal complexes being used in catalytic, 72 polymeric, 73 and redox chemistry, 74 the resulting metallomacrocyclic or metallosalphen complexes might bestow some interesting properties from their organic counterparts.  Amanda Gallant, a former PhD student in our group, discovered that Schiff-base macrocycle 42, having a crown-ether-like binding site in the pore, undergoes one-dimensional aggregation with the presence of alkali metal and ammonium salts, which was proven by NMR and UV-vis spectroscopies. 75 My PhD work originates from this aggregation behavior of macrocycle 42 and aims to study the structural morphology in solid form. Surprisingly, nanofibers were obtained when samples were viewed by electron microscopy after several attempts. This exciting result set the stage for my  52  research into constructing metal-containing fibrous superstructures through electrostatic assemblies and metal-ligand interactions. Understanding and rationalizing the morphological difference of the nanofibers have been one of the challenges during my PhD study.  My PhD research concentrates mainly on metal-containing nanofibers from Schiff-base macrocycles or zinc(II)-containing salphen complexes. The next chapter of this thesis focuses on the synthesis and characterization of a series of conjugated, hexagonal [6+6] Schiff-base macrocycles (40 and 41, Figure 1.40) that are obtained by condensing twelve individual components together in one step without the use of a template. They consist of six chelating sites for transition metals and possess a much bigger pore size than the macrocycles (e.g., 42, Figure 1.40) that were previously synthesized in our research group. Chapter 3 discusses the construction of hierarchical nanofibers assembled through electrostatic interactions from conjugated, triangular [3+3] Schiff-base macrocycles (42) that are able to bind alkali metal and ammonium cations within the central crown-ether-like pore. Supramolecular fibrous structures were obtained and studied by electron microscopy and solid-state NMR spectroscopy. In Chapter 4, the one-dimensional ion-induced self-assembly of macrocycle 42 with ammonium and alkali metal salts is extended to the formation of lyotropic liquid crystals, which can be generated from macrocycles with long alkoxy substituents in various organic solvents. Chapters 5, 6 and 7 discuss the synthesis and characterization of a series of zinc(II) salphen complexes (43 and 44, Figure 1.41) with linear and branched alkoxy, and carbohydrate peripheral substituents that form luminescent gels. Electron micrographs of the supramolecular assembles reveal nanofibers that are generated from metal-ligand 53  interactions between the zinc(II) center of a salphen unit and the neighboring phenolic oxygen, in which helical conformation was observed in some segments of the fibers. Finally, Chapter 8 summarizes the results of my PhD work and suggests future work in the area of self-assembled nanofibers through electrostatic and metal-ligand interactions.  OR  OR  RO  OR N N  N  HO  N  OH  OH  OR  OR  RO  HO  OR N  RO  N  OH  OH N  N  OR  N  HO  RO  N  OH  OH N  OH N  HO HO  OH  N  N  OH  OH  HO  OR  RO  N  OH  OH N  OR  RO  N  OH  OH N  OR  N  N  RO  OR OR  OR  40a R = C6H13 40b R = C5H11 40c R = H  OH RO  OR  N  HO HO  OH  N N  N  RO  OR OR  OH HO OH  OR  41 R = C6H13  HO  N  N HO  RO  N  N  N  OH N  RO  OR OR  42a R = C6H13 42b R = C4H9 42c R = C8H17 42d R = C10H21 42e R = C12H25  Figure 1.40. Chemical structures of Schiff-base macrocycles 40–42.  54  Figure 1.41. Chemical structures of zinc(II) salphen complexes 43–44.  55  1.5 References  1.  Ozin, G. A. Adv. Mater. 1992, 4, 612.  2.  Chichak, K. S.; Cantrill, S. J.; Pease, A. R.; Chiu, S.-H.; Cave, G. W. V.; Atwood, J. L.; Stoddart, J. F. Science 2004, 304, 1308.  3.  Hasenknopf, B.; Lehn, J.-M.; Kneisel, B. O.; Baum, G.; Fenske, D. Angew. Chem. Int. Ed. 1996, 35, 1838.  4.  Michels, J. J.; O’Connell, M. J.; Taylor, P. N.; Wilson, J. S.; Cacialli, F.; Anderson, H. L. Chem. Eur. 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P.; Swager, T. M. J. Am. Chem. Soc. 1999, 121, 8825. 75. Gallant, A, J.; MacLachlan, M. J. Angew. Chem. Int. Ed. 2003, 42, 5307.  64  CHAPTER 2 [6+6] SCHIFF-BASE MACROCYCLES †  2.1 Introduction  Large shape-persistent macrocycles are challenging synthetic targets, attractive for their novel properties, including liquid crystallinity and self-assembly.1–3 With a few exceptions, large organic macrocycles are prepared step-wise requiring sequences of protection, deprotection, reaction, and chromatographic separation, or requiring the elegant application of templates.4,5  Reversible reactions may permit self-assembly of macrocycles.6–8 The reversible condensation of an aldehyde and an amine to give an imine (Schiff-base condensation) is a convenient route to self-assemble macrocycles. This reaction has been used to assemble [2+2] and [3+3] Schiff-base macrocycles.9-11 The notation “[X+X] macrocycle” refers to a macrocycle formed by the condensation of X diamine moieties with X dialdehyde moieties. Using templates, even [4+4] Schiff-base macrocycles may be prepared.12 To date, no examples of larger Schiff-base macrocycles have been reported. This is not surprising given the vast number of possible products, the difficulty of purification, and their tendency to hydrolyze or undergo other side reactions (e.g., benzimidazole formation).13 Our group has been investigating large triangular [3+3] Schiff-base macrocycles prepared by †  A version of this chapter has been published as a communication: Hui, J. K.-H.; MacLachlan, M. J. “[6+6]  Schiff-base Macrocycles with 12 Imines: Giant Analogues of Cyclohexane” Chem. Commun. 2006, 2480.  65  condensation of six components in solution.14 In this chapter, the first examples of [6+6] Schiff-base macrocycles (40 and 41, Figure 2.1) are demonstrated. Remarkably, the preparation of these organic macrocycles involves the reaction of twelve individual components in solution to form twelve new covalent bonds.  Figure 2.1. Chemical structures of [6+6] Schiff-base macrocycles 40 and 41.  2.2 Results and Discussion  It is believed that condensation of 4,6-diformylresorcinol 45 with substituted phenylenediamine 46a could give macrocycle 40a. Recognizing that the reaction may be very sensitive to impurities, an intermediate compound 47a was prepared from the reaction of compound 45 with two equivalents of compound 46a, Scheme 2.1. This air-stable 66  intermediate is easily handled and avoids the need to use phenylenediamine 46a directly, a compound that is very air sensitive and difficult to purify.  RO O  O  HO  OR  OR  OR  + 2  N  OH H2N  45  OR  RO  NH2  46a R = C6H13 46b R = C5H11  H2N  HO  + 2H2O  N OH  NH2  47a R = C6H13 47b R = C5H11  Scheme 2.1. Synthetic route to air-stable compound 47.  Reaction of compound 45 with compound 47a afforded a mixture of oligomers as determined by MALDI-TOF mass spectrometry, Figure 2.2a. Significantly, the dominant species is the desired macrocycle 40a. Shorter oligomers are also observed, but they are open-chain oligomers rather than closed cycles.15 This reaction was repeated several times to ensure that macrocycle 40a was the principal component.  67  Figure 2.2. MALDI-TOF mass spectra of (a) crude reaction mixture from the preparation of macrocycle 40a and (b) purified macrocycle 40a. Insets: top (black): Isotope distribution obtained for macrocycle 40a; bottom (red): isotope distribution calculated for (40a+H)+.  Attempts to separate macrocycle 40a from the oligomeric by-products by silica gel, alumina, or size-exclusion chromatography failed to give pure macrocycle 40a (these compounds do not elute from silica). However, by taking advantage of the lower solubility of the macrocycle relative to oligomers, macrocycle 40a could be purified by trituration with hot methylene chloride. Figure 2.2b shows the MALDI-TOF spectrum of a sample of macrocycle after purification. Pure macrocycle 40a, which possesses 54 atoms in the smallest closed ring, was isolated in ca. 19% yield by this route. Although low, this yield is substantially higher than a statistical mixture of oligomers and cycles. This represents the first isolation of a Schiff-base macrocycle containing twelve imine bonds.  Macrocycle 40a gave satisfactory analysis. The IR spectrum of the deep red product 68  showed υC=N at 1631 cm-1, and confirmed that no aldehyde was present. The 1H NMR spectrum of macrocycle 40a was very broad, as this has seen with other macrocycles due to aggregation.16 Only broad features were observed, indicating the absence of starting materials and small oligomers. In particular, a broad imine resonance near 8.5 ppm, broad aromatic resonances, and no aldehyde resonance are consistent with the macrocycle.  Reaction of compound 45 with other phenylenediamines showed the [6+6] macrocycle as the major product (MALDI-TOF), with open-chain oligomers as the by-products. Macrocycle 40b with pentyloxy chains could be isolated in ca. 25% yield by a similar procedure to that for macrocycle 40a. When longer substituents were employed (e.g., decyloxy or dodecyloxy), the major product was the [6+6] macrocycle, but no suitable conditions was found to separate these macrocycles from oligomers due to their similar solubilities.  It may seem that the route to macrocycle 40 is not technically a [6+6] cyclization, but rather a [3+3] cyclization since it begins by pre-assembling compound 47. Under the reaction conditions, the imine bonds are formed and broken, so it does not matter that the larger component was used. In fact, the MALDI-TOF mass spectrum of the crude reaction mixture (Figure 2.2a) shows substantial quantities of oligomers with odd numbers of diamines (C, D, E, H, I, and J, Figure 2.3) that must arise from imine hydrolysis and recondensation. To demonstrate that the same macrocycle can truly be prepared by a [6+6] Schiff-base condensation, compound 45 was reacted with phenylenediamine 46a in chloroform/acetonitrile for 3 d. The MALDI-TOF spectrum of the crude product was similar to the product prepared using compound 47a, showing oligomers and macrocycle 69  40a. After purification, macrocycle 40a was obtained in very low yield (< 2%). The lower yield may be attributed to the difficulty of accurately obtaining the 1:1 stoichiometry of compounds 45 and 46a required for the formation of the [6+6] Schiff-base macrocycle.  70  Figure 2.3. Fragments observed in MALDI-TOF mass spectrum of crude macrocycle 40a. 71  To further verify that macrocycle 40a was prepared, a small sample of macrocycle 40a was reacted with excess vanadyl acetylacetonate in tetrahydrofuran. Vanadyl was selected for macrocycle 40a because each metal center tends to adopt a square pyramidal geometry and those six V=O bonds would be pointing either upward or downward randomly with respect to the plane of macrocycle. This would generate a mixture of isomers that originated from the vanadyl centers, which could prevent or minimize the columnar aggregation of the macrocyclic units and promote an enhancement in the solubility of the macrocycle. The MALDI-TOF mass spectrum of this product (Figure 2.4, m/z = 3020) showed that the metal-free macrocycle was no longer present and that the major product was the compound with six vanadyl groups (macrocycle 48, Figure 2.5). The incorporation of six metals into the product is consistent with the structure of macrocycle 40a, since each tetradentate N2O2 environment is expected to coordinate one metal ion.  Figure 2.4. MALDI-TOF mass spectrum of macrocycle 48.  72  Figure 2.5. Chemical structure of macrocycle 48.  As the Schiff-base condensation is reversible, thermodynamic products are obtained. By utilizing rigid precursors that are predisposed to a particular geometry, one can favour certain macrocycles to form. In the preparation of macrocycle 40a, ring-opened oligomers were observed, but only the [6+6] product15 is ring-closed. Once the oligomers have reached this length, they condense to form a stable macrocycle that maximizes hydrogen-bonding, has minimal strain, and precipitates from solution. These results suggest that by varying the geometry of the precursor, one may be able to access very large macrocycles, even beyond macrocycles 40.  To prove this hypothesis, naphthalene precursor 49 (Figure 2.6) was reacted with phenylenediamine 46a. The [6+6] Schiff-base macrocycle 41 was obtained in 78% yield 73  after trituration with hot methylene chloride. Elemental analysis, IR spectroscopy, and MALDI-TOF mass spectrometry verified that the [6+6] macrocycle was the major product. In this case, a higher yield was obtained due to the insolubility of the [6+6] macrocycle, causing it to precipitate from solution during the reaction. This insolubility prevented us from obtaining a 1H NMR spectrum of macrocycle 41. The macrocycle could also be prepared from a 1:2 compound analogous to compound 47.  O  O  HO  OH  49  Figure 2.6. Chemical structure of compound 49.  Semi-empirical calculations on macrocycle 40c metallated with nickel(II) were performed to determine the geometry and intramolecular distances of the [6+6] metallomacrocycles. Nickel was selected to ensure a square planar environment for simplicity. Calculations show that these metallomacrocycles with six nickel(II) centers will not be flat, but instead have two stable conformations that are similar to those of cyclohexane (Figure 2.7). The minimum energy conformation will be a boat (C2v symmetry) conformation, with the chair (D3d symmetry) conformation only ca. 3 kcal/mol higher in energy. The pore diameter of the giant metallomacrocycle is ca. 10.5 Å (cross-interior CH···HC distance for flat conformation). Semi-empirical calculations of the macrocycle metallated with six palladium(II) centers indicate that the larger metal will lead to more planar geometries.  74  Figure 2.7. Calculated structure of macrocycle 40c metallated with six nickel(II) ions (PM3): (a) view of chair (D3d) conformation; (b) view of boat (C2v) conformation. The hydrogen atoms have been removed for clarity. (Color legend: blue = nitrogen, gray = carbon, green = zinc and red = oxygen)  2.3 Conclusions  The first [6+6] Schiff-base macrocycles (40 and 41) have been synthesized and characterized. This one-pot assembly illustrates the utility of Schiff-base condensation to prepare large macrocycles. An improved synthesis of the macrocycles using new air-stable, isolable intermediate 47 in the preparation has also been discussed in this chapter. These 75  macrocycles are promising for studies in suparmolecular assembly.  2.4 Experimental  Materials: Deuterated solvents were obtained from Cambridge Isotope Laboratories, Inc.. Chloroform, acetonitrile and ethanol were purged with nitrogen gas before use. 4,6-Diformylresorcinol  (45),  4,5-dialkoxyphenylenediamine  (46)  and  3,6-diformyl-2,7-dihydroxynaphthalene (49) were prepared by literature methods.17–19  Equipment: All reactions were carried out under nitrogen unless otherwise noted. The 300 MHz 1H and 75.5 MHz 13C NMR spectra were recorded on a Bruker AV-300 spectrometer. IR spectra were obtained from dispersions in potassium bromide using a Bomens MB-series spectrometer. UV-vis spectra were performed in HPLC grade dichloromethane and distilled tetrahydrofuran on a Varian Cary 5000 UV-vis/near-IR spectrometer using a 1 cm cuvette. MALDI mass spectra were obtained at the UBC Microanalytical Services Laboratory on a Bruker Biflex IV TOF mass spectrometer equipped with a MALDI ion source. Samples were analyzed in a dithranol matrix. Electrospray ionization (ESI) mass spectra were obtained on a Bruker Esquire-LC ion trap mass spectrometer equipped with an electrospray ion source. High-resolution electrospray ionization (HR-ESI) mass spectra were obtained on a Micromass LCT time-of-flight (TOF) mass spectrometer equipped with an electrospray ion source. Samples for both ESI and HR-ESI were analyzed in methanol/dichloromethane at 1 μM. Leucine enkephalin-arg and Narasin were used as the references for HR-ESI. Melting points were obtained on a Fisher-John’s melting point  76  apparatus and are corrected. Isotope pattern simulations were performed with Isopro 3.0 (MS/MS  Software).  Fragments  were  calculated  using  ChemDraw  Ultra  8.0  (CambridgeSoft Corp., Cambridge, MA, USA).  Note about characterization: The characterization of the macrocycles proves unequivocally that the [6+6] macrocycles have been prepared. Attempts were made to obtain solution 1H NMR spectra of these macrocycles, but this has proven to be very difficult for 2 reasons: (1) solubility – the macrocycles are not very soluble in any solvents; and (2) aggregation – macrocycle 40a is barely soluble enough to obtain a 1H NMR spectrum, but it is always very broad and ill-defined. This was observed with other macrocycles and it is attributed to aggregation. Efforts to overcome this by using solvent mixtures or high temperature NMR were unsuccessful. It is not surprising that these macrocycles aggregate strongly in solution.  Synthesis  of  [6+6]  Schiff-base  Macrocycle  40a  via  Compound  47a.  4,6-Diformylresorcinol (45) (0.0334 g, 0.201 mmol) was added to a 100 mL Schlenk flask, which contained a solution mixture of chloroform (25 mL) and acetonitrile (30 mL), under nitrogen. Compound 47a (0.150 g, 0.201 mmol) was then added to the flask under nitrogen, giving a red solution. The mixture was stirred at 90 ºC for 24 h. A dark red precipitate that formed during the reaction period was isolated by filtration and followed by trituration with hot dichloromethane to yield macrocycle 40a (0.033 g, 19%, red solid).  77  Synthesis of [6+6] Schiff-base Macrocycle 40a (one-pot [6+6]). 4,6-Diformylresorcinol (45) (0.133 g, 0.803 mmol) and 4,5-dihexyloxyphenylenediamine (46a) (0.248 g, 0.803 mmol) were added to a 100 mL Schlenk flask under nitrogen. Chloroform (25 mL) and acetonitrile (30 mL) were added via syringe into the flask, giving an orange solution. The mixture was stirred under an atmosphere of nitrogen at 90 ºC, and the solution turned to deep red after stirring for a few hours. After 3 d at 90 ºC, the mixture was cooled to room temperature, at which point a red solid slowly precipitated out. The precipitate was isolated by filtration, triturated with hot dichloromethane, and dried under vacuum to yield macrocycle 40a (0.005g, 1.4%, red solid).  Data for [6+6] Schiff-base Macrocycle 40a. MALDI-TOF-MS: m/z = 2631.1. IR (KBr): υ = 3459 (m), 2929 (m), 2858 (s), 1631 (vs), 1509 (s), 1466 (m), 1333 (m), 1266 (m), 1177 (s), 1154 (s), 1000 (m), 846 (w), 755 (w), 698 (w) cm-1. UV-vis (tetrahydrofuran): λmax (ε) = 256 (1.30x104), 294 (1.95x104), 313 (2.00x104), 376 (1.79x104), 488 (9.91x105) nm (cm-1 mol-1 L). Anal. Cal’d (%) for 40a·H2O (C156H206N12O25): C 70.72, H 7.84, N 6.34; Found: C 70.59, H 7.85, N 6.61. m.p. = did not melt at 300 oC.  Synthesis of [6+6] Schiff-base Macrocycle 40b. Macrocycle 40b (25%, red solid) was prepared by the same procedure and purification as for macrocycle 40a via compound 47a.  Data for [6+6] Schiff-base Macrocycle 40b. MALDI-TOF-MS: m/z = 2463.3. IR (KBr): υ = 3427 (w), 2953 (s), 2932 (s), 2869 (m), 1628 (vs), 1607 (vs), 1579 (vs), 1507 (vs), 1468 (m), 1364 (m), 1321 (w), 1261 (s), 1177 (vs), 1158 (s) 1074 (w), 1048 (w), 989 (m), 929  78  (w), 890 (w), 848 (m), 729 (w) cm-1. Anal. Cal’d (%) for 40b ·4H2O (C144H188N12O28): C 68.22, H 7.47, N 6.63; Found: C 67.88, H 7.27, N 6.93. m.p. = did not melt at 300 oC. Synthesis  of  [6+6]  Schiff-base  3,6-Diformyl-2,7-dihydroxynaphthalene  Macrocycle (48)  (0.0271  41 g,  (one-pot 0.125  [6+6]).  mmol)  and  4,5-dihexyloxyphenylenediamine (46a) (0.0387 g, 0.125 mmol) were added to a 100 mL Schlenk flask under nitrogen. Chloroform (17.5 mL) and acetonitrile (17.5 mL) were added via syringe into the flask, giving an orange solution. The mixture was stirred under an atmosphere of nitrogen at 90 ºC for 2 d. An orange precipitate formed after stirring overnight, which was then isolated by filtration. The product was triturated with hot dichloromethane and dried under vacuum to yield macrocycle 41 (0.048 g, 78 %, orange solid).  Data for [6+6] Schiff-base Macrocycle 41. MALDI-TOF-MS: m/z = 2930.6. IR (KBr): υ = 2954 (s), 2929 (s), 2859 (s), 1638 (vs), 1606 (vs), 1502 (s), 1468 (s), 1408 (w), 1359 (s), 1260 (s), 1203 (m), 1143 (s), 1015 (m), 904 (w), 871 (w), 803 (m) cm-1. Anal. Cal’d (%) for 41·4H2O (C180H224N12O28): C 71.97, H 7.52, N 5.60; Found: C 71.83, H 7.43, N 5.78%. m.p. = did not melt at 300 oC.  Synthesis of Compound 47a. 4,6-Diformylresorcinol (45) (0.100 g, 0.602 mmol) and 4,5-dihexyloxyphenylenediamine (46a) (0.371 g, 1.20 mmol) were added to a 100 mL Schlenk flask under nitrogen. Ethanol (40 mL) was added via syringe into the flask, giving an orange solution and orange-red solid. The mixture was stirred at ambient temperature for 2 d, giving a red precipitate with an orange-red supernatant solution. The precipitate  79  was isolated by filtration and dried under vacuum to give compound 47a (0.425 g, 94%, red solid).  Data for Compound 47a. 1H NMR (300 MHz, chloroform-d1) δ 14.01 (s, 2H, OH), 8.43 (s, 2H, CH=N), 7.36 (s, 1H, aromatic CH), 6.71 (s, 2H, aromatic CH), 6.51 (s, 1H, aromatic CH), 6.32 (s, 2H, aromatic CH), 3.94 (t, 8H, OCH2), 3.86 (broad, 4H, NH2), 1.76 (m, 8H, CH2), 1.42 (m, 8H, CH2), 1.33 (m, 16H, CH2), 0.89 (t, 12H, CH3) ppm. 13C NMR (75.5 MHz, chloroform-d1) δ 166.7 (CH=N), 158.9, 151.8, 143.7, 137.8, 137.4, 127.8, 115.0, 107.8, 105.5, 103.8 (aromatic CH), 72.6, 70.6 (OCH2), 33.1, 33.0, 31.0, 30.6, 27.1, 24.0 (CH2), 15.4 (CH3) ppm. ESI-MS: m/z = 747.6 ((M+H)+), 769.6 ((M+Na)+). HR-ESI-MS for 47a+H+ (C44H67N4O6): 747.5061 (calculated), 747.5041 (found). IR (KBr): υ = 3394 (m), 3292 (w), 3168 (m), 2955 (s), 2928 (s), 2856 (s), 1634 (vs), 1576 (s), 1522 (vs), 1466 (s), 1429 (s), 1388 (m), 1363 (s), 1332 (s), 1289 (vs), 1261 (s), 1241 (s), 1229 (w), 1207 (m), 1178 (vs), 1165 (m), 1137 (m), 1069 (w), 1045 (m), 1014 (w), 997 (m), 951 (m), 930 (w), 906 (w), 872 (w), 838 (s), 787 (w), 758 (w), 721 (w) cm-1. UV-vis (methylene chloride): λmax (ε) = 262 (2.91x104), 289 (3.20x104), 418 (3.48x104) nm (cm-1 mol-1 L). m.p. = 120–121 oC.  Synthesis of Compound 47b. Compound 47b (97%, red solid) was prepared by the same procedure and purification as for compound 47a.  Data for Compound 47b. 1H NMR (300 MHz, chloroform-d1) δ 13.99 (s, 2H, OH), 8.47 (s, 2H, CH=N), 7.40 (s, 1H, aromatic CH), 6.73 (s, 2H, aromatic CH), 6.53 (s, 1H, aromatic CH), 6.35 (s, 2H, aromatic CH), 3.95 (t, 8H, OCH2), 3.78 (broad, 4H, NH2), 80  1.79 (m, 8H, CH2), 1.40 (m, 16H, CH2, 0.92 (t, 12H, CH3) ppm.  13  C NMR (75.5 MHz,  chloroform-d1) δ 165.2 (CH=N), 157.4, 157.3, 150.4, 142.2, 135.9, 126.4, 113.6, 106.4, 104.0, 102.3 (aromatic CH), 71.2, 69.1 (OCH2), 29.3, 28.9, 28.2, 22.5, 22.4 (CH2), 14.0 (CH3) ppm. ESI-MS: m/z = 691.4 ((M+H)+). HR-ESI-MS for 47b+H+ (C40H59N4O6): 691.4435 (calculated), 691.4440 (found). IR (KBr): υ = 3395 (w), 3177 (w), 2956 (s), 2932 (s), 2860 (m), 1629 (vs), 1521 (vs), 1509 (vs), 1467 (s), 1432 (s), 1389 (m), 1364 (m), 1330 (m), 1287 (s), 1261 (s), 1245 (m), 1205 (m), 1179 (s), 1135 (s), 1074 (w), 1051 (m), 1025 (m), 988 (m), 940 (w), 838 (s), 801 (m), 727 (w) cm-1. Anal. Calc’d (%) for 47b (C40H58N4O6): C 69.54, H 8.46, N 8.11; Found: C 69.55, H 8.10, N 8.50. m.p. = 127–128 oC.  81  2.5 References  1.  Semlyen, J. A. in Large Ring Molecules, J. Wiley & Sons, Chichester, 1996.  2.  (a) Grave, C.; Schlüter, A. D. Eur. J. Org. Chem. 2002, 3075. (b) Lehn, J.-M. Angew. Chem. Int. Ed. Engl. 1988, 27, 89. (c) Höger, S. J. Polym. Sci. Part A: Polym. Chem. 1999, 37, 2685.  3.  (a) Venkataraman, D.; Lee, S.; Zhang, J.; Moore, J. S. Nature, 1994, 371, 591. (b) Shimizu, L. S.; Hughes, A. D.; Smith, M. D.; Samuel, S. A.; Ciurtin-Smith, D. Supramol. Chem. 2005, 17, 27. (c) Mindyuk, O. Y.; Stetzer, M. R.; Heiney, P. A.; Nelson, J. C.; Moore, J. S. Adv. Mater. 1998, 10, 1363. (d) Höger, S.; Cheng, X. H.; Ramminger, A.-D.; Enkelmann, V.; Rapp, A.; Mondeshki, M.; Schnell, I. Angew. Chem. Int. Ed. 2005, 44, 2801. (e) Tobe, Y.; Utsumi, N.; Kawabata, K.; Nagano, A.; Adachi, K.; Araki, S.; Sonoda, M.; Hirose, K.; Naemura, K. J. Am. Chem. Soc. 2002, 124, 5350. (f) Xing, L.; Ziener, U.; Sutherland, T. C.; Cuccia, L. A. Chem. Commun. 2005, 5751.  4.  (a) Zhao, D.; Moore, J. S. Chem. Commun. 2003, 807. (b) Zhang, J.; Moore, J. S. J. Am. Chem. Soc. 1992, 114, 9701. (c) Staab, H. A.; Neunhoeffer, K. Synthesis 1974, 424. (d) Höger, S.; Enkelmann, V.; Bonrad, K.; Tschierske, C. Angew. Chem. Int. Ed. 2000, 39, 2267. (e) Höger, S.; Meckenstock, A.-D.; Müller, S. Chem. Eur. J. 1998, 4, 2423. (f) Grave, C.; Lentz, D.; Schäfer, A.; Samon, P.; Rabe, J. P.; Franke, P.; Schlüter, A. D. J. Am. Chem. Soc. 2003, 125, 6907.  5.  (a) Höger, S.; Morrison, D. L.; Enkelmann, V. J. Am. Chem. Soc. 2002, 124, 6734. (b) Fischer, M.; Höger, S. Eur. J. Org. Chem. 2003, 441. (c) Pyun, O. S.; Yang, W.;  82  Jeong, M.-Y.; Lee, S. H.; Kang, K. M.; Jeon, S.-J.; Cho, B. R. Tetrahedron Lett. 2003, 44, 5179. 6.  Bong, D. T.; Clark, T. D.; Granja, J. R.; Ghadiri, M. R. Angew. Chem. Int. Ed. 2001, 40, 988.  7.  (a) Zhang, W.; Moore, J. S. J. Am. Chem. Soc. 2004, 126, 12796. (b) Zhang, W. Moore, J. S. J. Am. Chem. Soc. 2005, 127, 11863. (c) Höger, S. Angew. Chem. Int. Ed. 2005, 44, 3806.  8.  (a) Otto, S.; Furlan, R. L. E.; Sanders, J. K. M. J. Am. Chem. Soc. 2000, 122, 12063. (b) Müller, A.; Serain, C. Acc. Chem. Res. 2000, 33, 2. (c) Leininger, S.; Schmitz, M.; Stang, P. J. Org. Lett. 1999, 1, 1921. (d) Jiang, H.; Lin, W. J. Am. Chem. Soc. 2004, 126, 7426. (e) Cacciapaglia, R.; Stefano, S. D.; Mandolini, L. J. Am. Chem. Soc. 2005, 127, 13666. (f) MacDonnell, F. M.; Ali, M. M. J. Am. Chem. Soc. 2000, 122, 11527.  9.  Vigato, P. A.; Tamburini, S. Coord. Chem. Rev. 2004, 248, 1717.  10. (a) Zhao, D.; Moore, J. S. J. Org. Chem. 2002, 67, 3548. (b) Shimakoshi, H.; Takemoto, H.; Aritome, I.; Hisaeda, Y. Tetrahedron Lett. 2002, 43, 4809. (c) Gao, J.; Reibenspies, J. H.; Zingaro, R. A.; Woolley, F. R.; Martell, A. E.; Clearfield, A. Inorg. Chem. 2005, 44, 232. (d) Givaja, G.; Blake, A. J.; Wilson, C.; Schröder, M.; Love, J. B. Chem. Commun. 2003, 2508. (e) Brooker, S. Coord. Chem. Rev. 2001, 222, 33. 11. (a) Akine, S.; Hashimoto, D.; Saiki, T.; Nabeshima, T. Tetrahedron Lett. 2004, 45, 4225. (b) Kwit, M.; Gawroński, J. Tetrahedron: Asymmetry 2003, 14, 1303. (c) Kuhnert, N.; Burzlaff, N.; Patel, C.; Lopez-Periago, A. Org. Biomol. Chem. 2005, 3, 1911. (d) Sessler, J. L.; Mody, T. D.; Lynch, V. M. J. Am. Chem. Soc. 1993, 115, 83  3346. 12. (a) McKee, V.; Shepard, W. B. J. Chem. Soc., Chem. Commun. 1985, 158. (b) Brooker, S.; McKee, V.; Shepard, W. B.; Pannell, L. K. J. Chem. Soc., Dalton Trans. 1987, 2555. (c) Brooker, S.; Kelly, R. J. J. Chem. Soc., Dalton Trans. 1996, 2117. (d) Christensen, A.; Jensen, H. S.; McKee, V.; McKenzie, C. J.; Munch, M. Inorg. Chem. 1997, 36, 6080. (e) Nakamura, Y.; Yonemura, M.; Arimura, K.; Usuki, N.; Ohba, M.; Okawa, H. Inorg. Chem. 2001, 40, 3739. (f) Kertsing, B.; Steinfeld, G.; Fritz, T.; Hausmann, J. Eur. J. Inorg. Chem. 1999, 2167. (g) Dutta, S. K.; Flörke, U.; Mohanta, S.; Nag, K. Inorg. Chem. 1998, 37, 5029. 13. Gallant, A. J.; Patrick, B. O.; MacLachlan, M. J. J. Org. Chem. 2004, 69, 8739. 14. (a) Gallant, A. J.; MacLachlan, M. J. Angew. Chem. Int. Ed. 2003, 42, 5307. (b) Gallant, A. J.; Hui, J. K.-H.; Zahariev, F. E.; Wang, Y. A.; MacLachlan, M. J. J. Org. Chem. 2005, 70, 7936. (c) Ma, C.; Lo, A.; Abdolmaleki, A.; MacLachlan,  M. J.  Org. Lett. 2004, 6, 3841. (d) Ma, C. T. L.; MacLachlan, M. J. Angew. Chem. Int. Ed. 2005, 44, 4178. (e) Gallant, A. J.; Sauer, M.; Yun, M.; Yeung, C. S.; MacLachlan, M. J. Org. Lett. 2005, 7, 4827. 15. A small quantity of a [5+5] Schiff-base macrocycle is observed in the crude reaction mixture (peak H in Figure 2.2a). No other macrocycles are observed. 16. (a) Ishi-i, T.; Hirashima, R.; Tsutsumi, N.; Amemori, S.; Matsuki, S.; Teshima, Y.; Kuwahara, R.; Mataka, S. J. Org. Chem. 2010, 75, 6858. (b) Petitjean, A.; Cuccia, L. A.; Schmutz, M.; Lehn, J.-M. J. Org. Chem. 2008, 73, 2481. (c) Liang, Y.; Jasbi, S. Z.; Haftchenary, S.; Morin, S.; Wilson, D. J. Biophys. Chem. 2009, 144, 1. 17. Worden, L. R.; Kaufman, K. D.; Smith, P. J.; Widiger, G. N. J. Chem. Soc., Chem. Commun. 1970, 227. 84  18. (a) Kim, D.-H.; Choi, M. J.; Chang, S.-K. Bull. Korean Chem. Soc. 2000, 21, 145. (b) Yilmaz, I.; Bekâroğlu, Ö. J. Chem. Res. 1998, (S) 374; (M) 1585. 19. Katz, T. J.; Liu, L.; Willmore, N. D.; Fox, J. M.; Rheingold, A. L.; Shi, S.; Nuckolls, C.; Rickman, B. H. J. Am. Chem. Soc. 1997, 119, 10054.  85  CHAPTER 3 ION-INDUCED SELF-ASSEMBLY OF [3+3] SCHIFF-BASE MACROCYCLES INTO NANOFIBERS WITH HIERARCHICAL ORGANIZATION †  3.1 Introduction  For many years, chemists have been looking to nature for inspiration in the development of new materials. 1 Natural materials such as cellulose 2 and spider silk 3 acquire their remarkable properties from the exquisite hierarchical organization of biomolecules, often extending over several length scales. For instance, collagen is a fibrous protein found in connective tissue2,4 (e.g., ligaments, skin, cartilage) and is the most abundant protein in mammals. Its usefulness arises from a complex, hierarchical structure whereby peptide chains organize into tropocollagen helices, which assemble into microfibrils, then aggregate into macrofibrils and even bundles of macrofibrils. 5 While synthesis of small molecules and crystalline solids is well-developed, understanding and controlling the self-assembly of molecules into organized materials is still in its infancy. †  A version of this chapter has been published as an article: Hui, J. K.-H.; Frischmann, P. D.; Tso, C.-H.;  Michal, C. A.; MacLachlan, M. J. “Spontaneous Hierarchical Assembly of Crown Ether-like Macrocycles into Nanofibers and Microfibers Induced by Alkali Metal and Ammonium Salts” Chem. Eur. J. 2010, 16, 2453.  86  The highly sophisticated organization of biomaterials is daunting to molecular chemists, but it is clear that understanding and harnessing the assembly of matter over several length scales will present opportunities for crafting innovative materials with advanced functions. Taking advantage of weak intermolecular interactions, such as π-π stacking, hydrogen-bonding, and coordination bonding, as well as hydrophobic effects, chemists have developed many beautiful structures, 6 , 7 but rarely do these exhibit multi-scale hierarchical assembly.  The organization of shape-persistent macrocycles into supramolecular structures is a promising way to develop new functional materials, 8 such as liquid crystals 9 and ion channels. 10 There are several reports of self-assembled fibers from shape-persistent macrocycles using hydrogen-bonding and π-stacking, 11 but alkali metals, where ionic interactions dominate, have not often been used to mediate the formation of supramolecular polymers. 12 This exclusion likely arises from the difficulties of controlling ionic interactions – they are non-directional and can act over a long distance. Höger reported isolated dimers constructed from charged shape-persistent macrocycles, but these did not further organize. 13 Davis has reported charged assemblies of calix[4]arene appended with four guanosine substituents upon the addition of NaBPh4 and the Na+ is located at the inner core of the cation-filled channel. 14 However, it was the intermolecular hydrogen bonding of the neighbouring guanosine units that led to aggregation. Electrostatic interactions have often been used to assemble multilayer thin films 15 and block copolymers, 16 but rarely in the formation of nanofibers with macrocyclic materials. 17 Controlling the level of hierarchical self-assembly of nanofibers remains a big challenge. 18 87  Biomolecules are often used as models for supramolecular assembly, and their organization can be facilitated by alkali cations. For instance, guanosine, a nucleoside comprising guanine attached to a ribose ring, can self-assemble into macrocyclic hydrogen-bonded tetramers (G-quartets) that are templated by alkali metal ions, namely Na+ and K+, which further vertically stack into columns with the cations being sandwiched between the layers of G-quartets. 19 This alkali metal ion-induced assembly yields hydrogels that are promising candidates for applications such as stimuli-responsive materials and sensors.19,20 A related G-quartet based on 5′-guanosine monophosphate (5′-GMP) has been shown to assemble into stacks, leading to G-quadruplexes. 21 Guanine-rich DNA segments have also been shown to assemble into extended structures with embedded ion channels through alkali- and alkaline-earth metal ion assembly. 22 These studies of biological self-assembly are important for developing new biosensors, and for understanding ion transport in natural systems.  In this chapter, the supramolecular assembly of triangular [3+3] Schiff-base macrocycle 42 (Figure 3.1) into polymers, nanofibers, and further into microfibrils is demonstrated. This multi-level hierarchical assembly is supported by micrographs and spectroscopic evidence for the structure, which is similar to the structural organization observed in guanosine-based fibers.  88  Figure 3.1. Chemical structure of [3+3] Schiff-base macrocycle 42.  3.2 Results and Discussion  3.2.1 Synthesis and Characterization of Nanofibers from Macrocycle 42 with Sodium Salts  Schiff-base macrocycle 42 23 is a conjugated molecule that resembles 18-crown-6 in the arrangement of six oxygen atoms in its interior. In contrast to crown ethers, however, the rigid backbone of macrocycle 42 prevents it from distorting sufficiently to offer an octahedral binding site for Na+. Amanda Gallant, a former PhD student in our group, previously showed that addition of NaBPh4 and other alkali metal tetraphenylborate salts to macrocycle 42 gives a spectroscopic signature for aggregation in solution. 24 With the addition of Na+, the color of the solution changes from orange to red, and the 1H NMR spectrum of macrocycle 42 shows large upfield changes in the resonances assigned to the  89  aromatic protons. These shifts are consistent with the formation of a one-dimensional assembly in solution, where the macrocycles are stacked on top of one another to share binding of the hydroxyl groups to the Na+. Moreover, aggregates were observed in solution by ESI mass spectrometry. The use of the tetraphenylborate anion was necessary to maintain solubility of the assemblies for solution-based studies. It is hypothesized that changing the anion from tetraphenylborate to a smaller anion (e.g.; tetrafluoroborate) would lead to the formation of fibers that could be observed by TEM.  When a solution of macrocycle 42a in chloroform was treated with excess NaBF4 (itself nearly insoluble in chloroform), a color change from orange to deep red was observed. The excess salts were filtered, and the solution became noticeably viscous after a few minutes (no gel formed, but a precipitate formed after standing for several minutes). Dynamic light scattering revealed a particle size of ca. 50 nm and the 1H NMR spectrum was broadened and upfield shifted, indicating aggregation of the macrocycles. 25 Samples were dried on TEM grids; Figures 3.2a,b show TEM images of [Na·42a]BF4 (composition confirmed by elemental analysis). Surprisingly, the sample is organized into a fibrous morphology, where the diameters of the fibers are ca. 170 nm, considerably larger than the diameter of macrocycle 42a (ca. 2–3 nm). SEM also revealed the three-dimensional structure of the fibers in the sample, Figures 3.2c,d. The bundles appear cylindrical in shape. AFM in tapping mode showed that the samples are relatively smooth and approximately the same size as observed by TEM, Figures 3.2e,f. Attempts to obtain images in contact mode resulted in sample destruction typical of soft materials. Similar structures were observed with a shorter chain analogue of macrocycle 42a (e.g., macrocycle 42b with butyloxy substituents) when combined with NaBF4. 90  Figure 3.2. (a,b) TEM, (c,d) SEM, and (e,f) AFM micrographs of [Na·42a]BF4. All samples were prepared by drop-casting a chloroform solution of [Na·42a]BF4 onto Formvar carbon-coated grids (TEM and AFM) or aluminum stubs (SEM) and dried at ambient condition.  As the formation of this fiber morphology was unexpected, the parameters in the assembly were explored. First, to verify that the assembly required the salt, control experiments were conducted by dissolving the macrocycle in chloroform, filtering, and  91  evaporating on a TEM grid. Electron microscopy showed no fiber structures over several attempts (Figure 3.3). With NaBF4 in the experiment, nanofibers were always observed.  Figure 3.3. Representative TEM image of macrocycle 42a deposited on a TEM grid without any salts  Second, to prove that this was not simply phase separation of the components during evaporation, powder X-ray diffraction (XRD) of a sample of [Na·42a]BF4 was compared with samples of NaBF4 and macrocycle 42a (prepared in the same way). Figure 3.4 shows the powder XRD patterns of these three samples. NaBF4 is a microcrystalline powder with no peaks at low angle and macrocycle 42a is microcrystalline with peaks between 5° and 30° 2θ. The powder XRD pattern of [Na·42a]BF4 shows a completely different pattern clearly contradicting simple phase separation of the components. The peaks for [Na·42a]BF4 are reproducible and index to a high symmetry (likely orthorhombic) lattice with large unit cell parameters, but a definitive unit cell could not be found as there are too few peaks observed. The peaks are at low angle (ca. 35 Å d-spacing) where peaks arising from inter-stack separations in a columnar organization of macrocycles would be expected. In addition, when comparing the IR spectra of both  92  macrocycle 42a and [Na·42a]BF4 (Figure 3.5), a small shift (10 cm-1) in the imine υC=N was observed, which indicates [Na·42a]BF4 is a new species from macrocycle 42a and NaBF4, instead of a result of phase separation.  Figure 3.4. Powder XRD patterns of [Na·42a]BF4 (blue), macrocycle 42a (black) and NaBF4 (red).  93  Figure 3.5. IR spectra of macrocycle 42a (red) and [Na·42a]BF4 (blue). Inset: expanded view of imine stretching band  To obtain further information about the role of the salt in the supramolecular assembly, we collaborated with Professor Carl Michal (Physics, UBC) to undertake solid-state NMR investigations.  23  Na NMR spectra of [Na·42a]BF4 revealed that  23  Na  experiences a large quadrupole coupling in the complex. As shown in Figure 3.6a, proton decoupling sharpens the  23  Na resonance considerably. Proton decoupling applied to a  sample of [Na·42a]BF4 where the hydroxyl protons were exchanged with deuterons produces a much less pronounced change, Figure 3.6b. These data provide strong evidence that the Na+ cations reside on the interior of the macrocycle, bonded to the hydroxyl groups. The hydroxyl deuteron is evidently highly labile, as it readily exchanged with 1H from atmospheric humidity. 19F decoupling produced no change in the spectra, indicating a substantial (> 4 Å) separation between the Na+ cations and the BF494  anions. The room-temperature 2H NMR spectrum, Figure 3.6c, shows a featureless broad line without any obvious singularities as would be expected from a well defined 2H quadrupole coupling. Cooling the sample to -50 °C produces changes to the lineshape that suggest some motional averaging is taking place. 11B NMR spectroscopy revealed a single, relatively sharp (2.4 kHz full-width at half-maximum) peak for the BF4- anions in [Na·42a]BF4, Figure 3.6d. A similar spectrum acquired from powdered NaBF4 (not shown) reveals a sharp (4 kHz) peak due to the central transition on top of a broad (100 kHz) powder pattern arising from the  11  B quadrupole coupling. The absence of the  11  B  quadrupole coupling in [Na·42a]BF4, along with the dramatically different T1 relaxation times (0.4 sec, compared to 22.4 sec in NaBF4) indicates that the BF4- anions are rapidly tumbling in the nanofibers. A simple calculation incorporating 11B quadrupolar relaxation and  11  B-19F dipolar relaxation in the short-correlation time limit suggests a rotational  correlation time on the order of 86 ns for the BF4- in the nanofibers.  95  Figure 3.6. Solid-state 23Na NMR spectra acquired with and without proton decoupling (dashed line and solid line, respectively) of (a) [Na·42a]BF4 and (b) [Na·42a]BF4 with hydroxyl deuterons. c) Solid-state 2H NMR spectra acquired at 21 and -50 oC. d) Solid-state 11B NMR spectrum of [Na·42a]BF4.  Based on these data, it is postulated that Na+ first coordinates to the hydroxyl groups inside macrocycles to form a polymer in solution (in a 1:1 ratio). This is also supported by the light scattering data, the 1H NMR shifts, and observation of oligomers by ESI mass spectrometry of macrocycle 42a upon addition of NaBF4 (Figure 3.7).  96  Figure 3.7. ESI mass spectrum of [Na·42a]BF4 in methanol/methylene chloride mixture.  In order to probe the surface composition of the fibers, attempts were made to exchange both the anions and cations of the nanofibers, and then examined them by energy dispersive X-ray (EDX) analysis. TEM grids with fibers of [Na·42a]BF4 were immersed in saturated aqueous solutions of NaPF6 or KPF6, followed by repeated rinsing with water. An EDX measurement was first performed on the fibers with [Na·42a]BF4 as a control and the signals corresponding to carbon, oxygen, fluorine and sodium can be seen in the spectrum (boron’s signal could not be observed because it was hidden underneath carbon’s signal). The EDX spectra obtained from the samples exchanged with the PF6- salts showed the same pattern as the control plus a new signal attributed to phosphorus of the counter-anion, suggesting some of the surface anions of the fibers  97  could be exchanged. However, when KPF6 was used for the wash, no K+ was observed by EDX, indicating that the Na+ in the fibers is not readily exchanged. These results support the presence of tightly bound cations inside the fibers with exchangeable anions around the periphery.  If the macrocycles are stacked on top of one another with Na+ bridging, then introducing bulky substituents should block the assembly. To test this, Peter Frischmann prepared the new compound 1,4-diformyl-2,3-dihydroxytriptycene (50) as shown in Scheme 3.1. Reaction of compound 50 with 4,5-dihexyloxyphenylenediamine (46a) afforded Schiff-base macrocycle 51 in 51% yield. The structure of the new macrocycle with bulky triptycenyl substituents was verified by NMR spectroscopy, mass spectrometry, and elemental analysis. Under identical experimental conditions employed for the assembly of macrocycle 42a, macrocycle 51 displayed no evidence of columnar aggregation (1H NMR spectrum in solution) for binding to either NaBPh4 or NaBF4, supporting the assertion that the stacking is important in the assembly of the polyelectrolyte. Furthermore, drop-casting a chloroform solution of macrocycle 51 with NaBF4 (prepared under the same conditions) onto a TEM grid and imaging the dried sample revealed only ill-defined aggregates (Figure 3.8). In the case of macrocycle 51, the bulky triptycenyl groups prevent columnar assembly and, therefore, no fibrous structure was observed.  98  Scheme 3.1. Syntheses of (a) 1,4-diformyl-2,3-dihydroxytriptycene (50).  macrocycle  51  and  (b)  Figure 3.8. TEM image of macrocycle 51 with NaBF4.  99  The polymer from macrocycle 42a and Na+ is a highly charged rod-like assembly with the anions located outside of the macrocycles, but electrostatically bound to the positively charged polymer. The exact length of the polymers is uncertain, but light scattering measurements suggest they are quite long at this stage in solution (an average size of 50 nm was observed, assuming a spherical shape). During evaporation and concentration, 26 the charge-balancing anions are attracted to other positively charged rods and the assembly organizes into nanofibers. Overall, the Na+ cations are bound inside the macrocycle assembly, but the BF4- anions are only loosely bound, consistent with the solid-state NMR data and EDX analysis.  When larger anions were employed (e.g., BPh4-), the fibers obtained were of much lower quality – they were short and poorly defined (Figure 3.9). This is also consistent with our model where the anions are situated between the charged polymer rods, and large anions would be expected to disrupt the organization.  Figure 3.9. (a,b) TEM images of macrocycle 42a with NaBPh4.  In an effort to control the fiber growth, evaporation was conducted at different rates. 100  TEM images of samples prepared with rapid evaporation revealed short fibers, Figure 3.10. In contrast, very long, well-organized fibers were obtained with slow evaporation rates. These fractal structures, obtained from molecular assembly, resemble morphologies observed in amphiphiles and block copolymers. 27 The evaporation rate can be used to control the length of the fibers prepared.  Figure 3.10. (a,b) The solvent was evaporated in 10 sec at 92 oC. (c,d) The sample was dried inside a vial (in 80–90 min), which helped to slow down the evaporation of the solvent.  Macrocycle 42a binds Na+ in its interior to form a highly charged polymer, where alkali metals are bound to the macrocycles through Na···O interactions. These aggregates further condense into a much larger nanofibrillar bundle via electrostatic interactions 101  between the anions and the polyelectrolyte. Potassium salts behave similarly, though the fiber quality is generally poorer than for sodium. This electrostatic self-assembly is reminiscent of the organization of actin filaments, which have supramolecular structures that are still poorly understood and not easily mimicked by synthetic models. 28  3.2.2 Synthesis and Characterization of Nanofibers from Macrocycle 42 with Ammonium Salts  With NH4BF4 used in the place of NaBF4, an additional level of hierarchy was observed. Spectroscopically, NH4+ behaves very similarly to Na+ when added to a solution of macrocycle 42a, forming one-dimensional polymeric structures with the NH4+ cations hydrogen-bonding in the interior of the macrocycles.24 Remarkably, the nanofibers further assemble into bundles (microfibers) with diameters of hundreds of microns and lengths of millimeters – they look like (orange) hair. Figure 3.11a shows an optical micrograph of the microfibrils; under crossed polarizers the samples are birefringent, indicating the fibers are anisotropic (Figure 3.12). It is noteworthy that each individual ″hair″ observed under the optical microscope is in fact a bundle of nanofibers. When deposited on a TEM grid, nanofibers with diameters of ca. 200 nm were noticed (Figures 3.11b,c). This feature can be seen clearly by SEM (Figures 3.11d,e) and AFM (Figures 3.11f,g). Similar structures were observed with a shorter chain analogue of macrocycle 42a (e.g., macrocycle 42b with butyloxy substituents) when combined with NH4BF4.  102  Figure 3.11. (a) Optical, (b,c) TEM, (d,e) SEM, and (f,g) AFM (height trace and amplitude trace, respectively) micrographs of macrocycle 42a with NH4BF4. The sample has been negatively-stained with chromium for better contrast in (e). 103  Figure 3.12. (a–c) Optical micrographs of the microfibrils from macrocycle 42a and NH4BF4 under the crossed polarizers.  In fact, these structures can be assembled directly from the precursors to macrocycle 42a (4,5-dihexyloxyphenylenediamine (46a) and 3,6-diformylcatechol) with addition of NH4BF4, demonstrating another level of hierarchy in the one-pot assembly. The microfibers are similar to those obtained from using macrocycle 42a directly, but shorter and finer. The size difference is attributed to the presence of oligomers that can act as impurities and interfere with fiber formation. Thus, a four-level hierarchical assembly was observed that spans six orders of magnitude in length (from nm to mm) whereby the precursors to macrocycle 42a (dimensions of ca. 0.5 nm) react to form macrocycle 42a (diameter of ca. 2–3 nm), which assembles into an electrolytic polymer, then further organizes into nanofibers and microfibers (Figure 3.13). The graphic representation illustrates the self-assembly, but may be an oversimplification as both the longitudinal and transverse assembly could occur simultaneously.  104  Figure 3.13. A graphic representation of the four-level hierarchical assembly. In the first step, dialdehyde and diamine precursors assemble into macrocycles. Upon reaction with NH4BF4, these form polyelectrolytes that organize into nanofibers. In the final step, the nanofibers bundle into microfibers.  3.3 Conclusions  Schiff-base macrocycles having a central crown ether-like interior were combined with alkali metal and ammonium salts to generate fibrous structures. The nanofibers and microfibers formed via ion-induced hierarchical self-assembly of the macrocycles with NaBF4 and NH4BF4 were extensively studied by TEM, SEM and AFM, and with an  105  optical microscope. It is believed that the cations first bind to the interior of the macrocycles to form one-dimensional aggregates that are surrounded by the counteranions of the salts on the outside. Through electrostatic interactions, these highly charged polymers then further organize into nanofibers or microfibers. It was also found that dimensions of the fibers are affected by the evaporation rate of the solvent. This hierarchical structural organization is similar to the construction of guanosine-based fibrils and other fibrous structures from nature, and may offer a model for the hierarchical construction of biomimetic materials. Electrostatic self-assembly of nanofibers may prove useful for preparing functional materials and for understanding organization in biological materials.  3.4 Experimental  General Procedures: All reactions were carried out under nitrogen atmosphere by means of standard Schlenk techniques unless otherwise stated. Anhydrous diethyl ether was distilled from sodium/benzophenone under nitrogen. Methylene chloride was dried by passage  over  an  alumina  column  under  nitrogen.  Anhydrous  N,N,N′,N′-tetramethylethylenediamine (TMEDA) was distilled from potassium hydroxide pellets. Acetonitrile, methanol, ethyl acetate and toluene were purged with nitrogen before use. Deuterated solvents were obtained from Cambridge Isotope Laboratories, Inc.. All reagents were used as received unless otherwise stated. Copper(I) bromide, 25 wt% sodium methoxide in methanol, butyllithium (1.6 M in hexanes), anhydrous DMF, TMEDA, boron tribromide, sodium tetrafluoroborate, sodium hexafluorophosphate,  106  potassium hexafluorophosphate, and ammonium tetrafluoroborate were obtained from Aldrich.  The  syntheses  of  [3+3]  Schiff-base  macrocycles  42a  and  42b,23  4,5-dihexyloxyphenylenediame (46a) 29 and 2,3-dibromotriptycene (50) 30 were carried out according to literature procedures. Previously characterized 2,3-dimethoxytriptycene (52), 31 was prepared by an alternate route reported here.  Equipment: TEM and SEM were performed at the UBC BioImaging Facility. TEM and SEM images were obtained on a Hitachi H7600 transmission electron microscope and a Hitachi S-4700 field emission scanning electron microscope, respectively. AFM was performed on an Asylum Research MFP-3D-SA atomic force microscope. An Olympus AC 240TM silicon cantilever was used in tapping (ac) mode. EDX measurements were obtained on a Hitachi H-800 transmission electron microscope at the Electron Microscope Laboratory of the UBC Materials Engineering Department. An Olympus BX41 polarizing optical microscopy (POM) equipped with a digital camera was used to observe the microfibrils shown in Figures 3.9a and 3.10. All solid-state NMR experiments were performed on a home-built NMR spectrometer based upon an Oxford Instruments 8.4 T wide-bore magnet at the Michal research group of UBC Physics and Astronomy Department. 32 Hydroxyl-deuterated [Na·42a]BF4 was prepared by exposing [Na·42a]BF4 to D2O vapor for 48 h, and then the sample was placed in a dessicator for 48 h.  23  Na experienced a large quadrupole coupling in the complex, as the observed  resonance arose from the central transition only, made clear from the fact that the effective rf field strength was found to be a factor of 2 greater (100 kHz vs 50 kHz) than that measured for an 0.1 M aqueous NaCl referenced at the same rf power level. This is consistent with the factor of I + 1/2 expected for excitation of the central transition and I 107  = 3/2. Powder XRD data were recorded on a D8 Advance powder X-ray diffractometer by drop-casting the chloroform solutions of macrocycle 42a and [Na·42a]BF4 onto silicon plates and the NaBF4 sample was prepared by the standard method. Mass spectra and elemental analyses were obtained at the UBC Microanalytical Services Laboratory. ESI mass spectra were obtained on a Micromass LCT TOF mass spectrometer equipped with an electrospray ion source. Atmospheric pressure chemical ionization (APCI) was obtained on a Waters ZQ mass spectrometer equipped with an ESCI ion source. Samples for both ESI and APCI were analyzed in methanol or methanol/methylene chloride mixture at 1 μM. MALDI mass spectra were obtained on a Bruker Biflex IV TOF mass spectrometer equipped with a MALDI ion source and dithranol was used as the matrix. Elemental analyses were obtained on a Carlo Erba Elemental Analyzer EA 1108. The particle size analysis data was collected at 25 oC with the Malvern Zetasizer Model Nano-ZS in chloroform a 1 cm glass cuvette. IR spectra were obtained using a Thermo Scientific Nicolet 6700 FT-IR spectrometer equipped with the diamond Attenuated Total Reflectance. UV-vis spectra were performed in methylene chloride on a Varian Cary 5000 UV-vis/near-IR spectrometer using a 1 cm cuvette.  Synthesis of 2,3-Dimethoxytriptycene (52). A mixture of 2,3-dibromotriptycene (1.00 g, 2.44 mmol), copper(I) bromide (0.079 g, 0.55 mmol), 25 wt% sodium methoxide in methanol (5 mL, 22 mmol), ethyl acetate (0.5 mL), and toluene (10 mL) was heated at reflux for 18 h. The solution was cooled to room temperature then quenched with the addition of water. After extracting the aqueous layer with methylene chloride, the combined organic layers were dried over anhydrous magnesium sulfate and filtered. The  108  solvent was removed by rotary evaporation to give compound 52 (0.652 g, 85%, white solid).  Data for 2,3-Dimethoxytriptycene (52). 1H NMR (400 MHz, chloroform-d1) δ 7.37 (m, 4H, aromatic CH), 7.03 (s, 2H, aromatic CH), 6.99 (m, 4H, aromatic CH), 5.35 (s, 2H, bridgehead H), 3.84 (s, 6H, OCH3) ppm. The 1H NMR data are consistent with the literature values.31  Synthesis of 1,4-Diformyl-2,3-dimethoxytriptycene (53). Anhydrous TMEDA (5.30 mL, 35.3 mmol) was added to a solution of 2,3-dimethoxytriptycene (52) (4.589 g, 14.7 mmol) in anhydrous diethyl ether (20 mL). The cloudy solution was cooled to 0 °C, butyllithium (1.6 M in hexanes, 40 mL, 58.8 mmol) was added dropwise over 30 min, and the brown suspension was then stirred for 16 h at ambient temperature. Anhydrous DMF (5.10 mL, 66.0 mmol) was added and the suspension was stirred for 30 min, followed by acidification with dilute hydrochloric acid and extraction with diethyl ether. The combined organic layers were dried with sodium sulfate, filtered, and the solvent was removed by rotary evaporation. The crude product was then purified by chromatography on silica gel (2:1 hexanes/methylene chloride) to elute the first yellow band. Rotary evaporation of the yellow solution yielded compound 53 (2.285 g, 42%, yellow solid).  Data  for  1,4-Diformyl-2,3-dimethoxytriptycene  (53).  1  H  NMR  (400  MHz,  chloroform-d1) δ 10.57 (s, 2H, C(O)H), 7.46 (m, 4H, aromatic CH), 7.04 (m, 4H, aromatic CH), 6.86 (s, 2H, bridgehead H), 3.91 (s, 6H, OCH3) ppm.  13  C NMR (100.6  MHz, chloroform-d1) δ 191.9 (C(O)H), 152.8, 144.6, 144.1, 129.1, 125.6, 124.3 109  (aromatic C), 62.2 (OCH3), 47.9 (bridgehead C) ppm. APCI-MS: m/z = 371 ((M+H)+). IR: υ = 3004, 2972, 2937, 2858, 1687, 1562, 1444, 1379, 1300, 1260, 1132, 1156, 1069, 1013, 986, 946, 746, 578 cm-1. UV-vis (methylene chloride): λmax (ε) = 273 (2.2 x 104), 278 (2.2 x 104), 373 (7.8 x 103) nm (cm-1 mol-1 L). Anal. Calc’d (%) for 53 (C24H18O4): C 77.82, H 4.90; Found: C 77.61, H 4.85. m.p. = 190–192 °C.  Synthesis  of  1,4-Diformyl-2,3-dihydroxytriptycene  (50).  1,4-Diformyl-2,3-dimethoxytriptycene (53) was dissolved in anhydrous methylene chloride (200 mL). The yellow solution was cooled to 0 °C and boron tribromide (2.60 mL, 27.5 mmol) was added yielding a fuming pink solution. After the reaction stirred at ambient temperature for 16 h, the solution was poured onto ice and extracted with methylene chloride. The combined organic fractions were dried with magnesium sulfate, filtered, and the solvent was removed by rotary evaporation yielding compound 50 (1.962 g, 93%, orange solid).  Data  for  1,4-Diformyl-2,3-dihydroxytriptycene  (50).  1  H  NMR  (400  MHz,  chloroform-d1) δ 10.80 (s, 2H, OH), 10.69 (s, 2H, C(O)H), 7.44 (m, 4H, aromatic CH), 7.07 (m, 4H, aromatic CH), 6.23 (s, 2H, bridgehead H) ppm.  13  C NMR (100.6 MHz,  chloroform-d1) δ 193.5 (C(O)H), 147.0, 144.1, 139.7, 125.9, 123.8, 119.4 (aromatic C), 47.3 (bridgehead C) ppm. ESI-MS: m/z = 341.3 ((M-H)-). IR: υ = 3041, 2996, 2922, 2852, 1644, 1556, 1458, 1436, 2895, 1273, 1198, 962, 921, 761, 675, 625, 600, 568 cm-1. UV-vis (methylene chloride): λmax (ε) = 253 (6.5 x 103), 294 (1.9 x 104), 453 (4.9 x 103) nm (cm-1 mol-1 L). Anal. Calc’d (%) for 50 (C22H14O4): C 77.18, H 4.12; Found: C 76.83, H 4.19. m.p. = decomposed around 220° C. 110  Synthesis  of  Triptycene-based  [3+3]  Schiff-base  Macrocycle  (51).  1,4-Diformyl-2,3-dihydroxytriptycene (50) (0.035 g, 0.10 mmol) was added to a solution of 4,5-dihexyloxyphenylenediamine (46a) (0.032 g, 0.10 mmol) in acetonitrile (6 mL). The deep red solution was stirred at 90 oC for 14 h. After cooling to room temperature, it was cooled at -10 °C for 48 h to obtain red precipitate. The solid was filtered and dried under vacuum to yield macrocycle 51 (0.032 g, 51%, orange solid). Data for Triptycene-based [3+3] Schiff-base Macrocycle (51). 1H NMR (400 MHz, chloroform-d1) δ 13.04 (s, 6H, OH), 9.27 (s, 6H, CH=N), 7.18 (m, 12H, aromatic CH), 7.00 (s, 6H, aromatic CH), 6.80 (m, 12H, aromatic CH), 5.83 (s, 6H, bridgehead H), 4.23 (t, 12H, OCH2), 1.97 (m, 12H, CH2), 1.62 (m, 12H, CH2), 1.45 (m, 24H, CH2), 0.98 (t, 18H, CH3) ppm.  13  C NMR (100.6 MHz, chloroform-d1) δ 159.3 (CH=N), 149.4, 147.5,  145.0, 136.4, 136.0, 125.2, 123.2, 116.6, 107.0 (aromatic C), 70.4 (OCH2), 48.5 (bridgehead C), 31.7, 29.4, 25.8, 22.7 (CH2), 14.1 (CH3) ppm. ESI-MS: m/z = 1844.6 ((M+H)+), 1867.6 ((M+Na)+), 1883.4 ((M+K)+). IR: υ = 3726, 3708, 3627, 2925, 2854, 1606, 1506, 1462, 1426, 1375, 1304, 1257, 1173, 1115, 990, 759, 741, 624 cm-1. UV-vis (methylene chloride): λmax (ε) = 284 (5.8 x 104), 330 (7.1 x 104), 417 (1.2 x 105) nm (cm-1 mol-1 L). Anal. Calc’d (%) for 51·H2O (C120H128N6O13): C 77.39, H 6.93, N 4.51; Found: C 77.63, H 7.28, N 4.52. m.p. = did not melt at 260 °C.  Sample Preparation of [Na·42a]BF4 for TEM Imaging. Schiff-base macrocycle 42a (1.5 mg, 1.1 μmol) was dissolved in chloroform (1 mL) and was mixed with an excess amount of sodium tetrafluoroborate (50 mg, 4.5 mmol) for 5 sec to give a dark red solution. The solution was allowed to stand for 5 min, before removing the excess sodium 111  tetrafluoroborate by filtration through a Kimwipe pad. The dark red solution was then diluted to half of its concentration before drop-casting onto the Formvar carbon-coated grid. The coated grid was dried at ambient conditions. To prepare the sample with rapid evaporation, the coated grid was dried at 92 oC in 10 sec. To prepare the sample with slow evaporation, the coated grid was dried in a partially closed vial at ambient temperature in 80-90 min.  Preparation of the Microfibrils from Macrocycle 42a and NH4BF4. 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Instrum. 2002, 73, 453.  117  CHAPTER 4 ION-INDUCED SELF-ASSEMBLY OF [3+3] SCHIFF-BASE MACROCYCLES INTO LYOTROPIC LIQUID CRYSTALS†  4.1 Introduction  Liquid crystals (LCs) are an important class of materials that are applied to a variety of applications, notably temperature sensors 1 and displays. 2 These applications utilize thermotropic LCs, which form a temperature-dependent liquid crystalline phase between the crystalline state and the isotropic melt. A large number of organic and inorganic substances have been investigated that exhibit thermotropic liquid crystallinity.  Lyotropic LCs, on the other hand, form liquid crystalline phases in solution where the molecules organize into micelles, nematic, hexagonal, and other phases. 3 Typically, lyotropic LCs are formed in water by amphiphilic molecules (surfactants). 4 Numerous compounds that exhibit lyotropic mesomorphism have been found to have good anisotropic ionic conductivities. 5 G-quartets are known to form rigid rods in aqueous solution that organize into lyotropic LC phases. 6 However, lyotropic LCs formed in non-polar solvents are rare, but are promising as an organizational method for constructing supramolecular  †  A version of this chapter will be submitted for publication as a communication: Hui, J. K.-H.; MacLachlan,  M. J. “Ion-Induced Columnar Assembly of Lyotropic Ionic Liquid Crystals from Schiff-base Macrocycles”.  118  materials. 7  This chapter describes investigations of lyotropic LCs formed by macrocycle-cation complexes from triangular [3+3] Schiff-base macrocycle 42 with long alkoxy peripheral substituents (Figure 4.1). These species form LCs in chloroform, toluene, and chlorobenzene. Based on an amphiphilic tubular structure from the ion-induced assembly of Schiff-base macrocycles, these mesogens represent a very unusual motif for observing liquid crystallinity. These new columnar nematic LC phases may serve as templates for constructing ion-conducting lyotropic phases or as templates for new mesoporous materials formed in non-aqueous solvent.  RO  N  OR  N  OH HO OH  HO  N  N HO  RO  N  OH N  RO  OR OR  42a R = C6H13 42b R = C4H9 42c R = C12H25 42d R = C8H17 42e R = C10H21  Figure 4.1. Chemical structure of macrocycle 42 with long alkoxy substituents.  119  4.2 Results and Discussion  In Chapter 3, a series of conjugated, triangular [3+3] Schiff-base macrocycles 42 having two peripheral alkoxy substituents on each phenylenediimine unit have been prepared. 8 The macrocycles with hexyloxy and butyloxy side chains (macrocycles 42a and 42b) organize into hierarchically-organized nanofibers upon addition of alkali metal or ammonium salts, 9 with the cations situated in the center of a tubular column of macrocycles. This polycationic macrocycle assembly is charge balanced by counteranions located outside of the columnar aggregates.  As macrocycles 42a-e have the same symmetry (D3h) as the well-known family of mesogens, hexakis(alkoxy)triphenylenes, 10 it is postulated that macrocycles 42 could form liquid crystalline phases. Previous attempts to impart liquid crystallinity upon macrocycles 42 by introducing long alkyl chains led only to substances with reduced melting points, but no liquid crystallinity.8  Chloroform solutions of macrocycle 42c failed to show any birefringence, even when concentrated. However, when chloroform solutions of macrocycle 42c with NH4BF4 (1:1) were viewed under crossed polarizers with a polarizing optical microscope (POM), surprisingly, a texture characteristic of a nematic LC was observed (Figure 4.2a). The lyotropic mesomorphism was apparent at a concentration of ca. 10 wt% and higher (before solidification). In the LC phase, the samples were relatively viscous but fluid.  120  Figure 4.2. Optical micrographs of chloroform solutions of NH4BF4 with macrocycles (a) 42c, (b) 42e and (c,d) 42d (1:1 ratio of 42:NH4+) show typical textures observed for the LC samples under crossed polarizers. Samples were viewed between a slide and a cover slip as the solvent evaporated from samples that were ca. 10 wt%.  Based on our results with the shorter chain analogues (macrocycles 42a and 42b), 11 it is believed that upon addition of NH4BF4, macrocycle 42c binds the cation in its interior and forms a polyelectrolyte. This is supported by NMR data; when NH4BF4 was added to macrocycle 42c, severe line broadening and shifting were observed as with macrocycle 42a. 1211 In the case of macrocycles 42a and 42b, the assemblies subsequently organize into insoluble fibers through electrostatic interactions.9 With longer chains present in macrocycle 42, however, the rod-shaped polyelectrolytes are more soluble and instead form a lyotropic LC in solution. Unlike macrocycles 42a and 42b with shorter alkoxy chains that 121  allow the columnar aggregates to pack into nanofibers, long dodecyloxy chains on macrocycle 42c render the columnar aggregates more soluble (Figure 4.3). The macrocycles retain the one-dimensional ion-induced tubular assembly and organize with some long-range orientational order in terms of the alignment of the columns, giving the columnar nematic (Nc) phase.  Figure 4.3. Ion-induced assembly leading to the formation of lyotropic liquid crystals. (a) In solvent, macrocycle 42c–e combine with cations (yellow spheres) to form a one-dimensional polymeric structure where the macrocycles are bridged by the cations. (b) Upon concentration, these one-dimensional assemblies organize into a nematic liquid crystal phase where they retain orientational order. The counteranions have been omitted for clarity.  122  Addition of NH4BF4 to macrocycles 42d and 42e having octyloxy and decyloxy chains, respectively, also led to birefringent chloroform solutions. The optical micrograph of macrocycle 42e with NH4BF4 displays a texture (Figure 4.2b) that is similar to that observed for 42c and characteristic of a nematic mesophase. Macrocycle 42d, however, showed different textures – ones similar to Figures 4.2a,b were observed, but also an unusual mesh texture was observed near the edges of a droplet (Figures 4.2c,d). It appears that the transition between nanofibers and liquid crystals occurs between hexyloxy and octyloxy substituents for the macrocycles.  To investigate the scope of mesophase formation in this system, studies were performed by varying the ions and the solvent. When macrocycle 42c was combined with LiBF4 or NaBF4 in chloroform, nematic mesophases were identified by POM (Figures 4.4a,b). In addition, macrocycle 42c was mixed with NH4BPh4 in order to observe the effect of counteranions on the morphology of the LC phase. Surprisingly, even with the bulky BPh4- anion, liquid crystallinity was observed. Furthermore, the sample of macrocycle 42c with NH4BF4 was prepared in different solvents, namely toluene and chlorobenzene (Figures 4.4c,d). Once again, nematic mesophases were imaged by POM and the textures are similar to the one prepared in chloroform. These results show that the lyotropic mesomorphism is robust and can be observed with diverse cations, anions, and non-polar solvents.  123  Figure 4.4. Optical micrographs of macrocycle 42c with (a) LiBF4 in chloroform, (b) NaBF4 in chloroform, (c) NH4BF4 in toluene, and (d) NH4BF4 in chlorobenzene.  Efforts to obtain XRD from solutions of NH4+ complexes of 42c–e in chloroform (where they are liquid crystalline) were futile owing to insufficient diffraction – only a very broad halo centered near 22° 2θ could be seen. Instead, XRD studies of films prepared from the dried liquid crystal samples were undertaken. IR spectra of the thin films were nearly identical and verified the structural integrity of the macrocycle. Notably, the υC=N stretching mode observed at 1609 cm-1 in the free macrocycle is present at 1618 cm-1 in all of the alkali metal and ammonium tetrafluoroborate complexes. Although these thin films are not in the lyotropic LC phase themselves, XRD of the films should give an indication of the order present in the sample prior to drying. XRD patterns of dried samples of macrocycles  124  42c–e with NH4BF4 all displayed one strong, broad diffraction peak with d-spacing of ca. 24.8, 25.4 and 26.9 Å, respectively (Figure 4.5a). From rough modelling of a hypothetical tubular assembly, this diffraction peak corresponds quite well to the expected inter-stack separation rather than inter-macrocycle separation within a column (Figure 4.6). As well, the increase in the d-spacing with increasing chain length agrees with this interpretation. The absence of additional diffraction peaks is also consistent with a poorly organized structure, as expected for a nematic liquid crystal. XRD of macrocycle 42c with LiBF4 and NaBF4 was also measured for comparison with the diffraction pattern of the NH4BF4 sample in order to get more information on the effect of cations on the liquid crystallinity. All three XRD patterns have a strong diffraction peak at 26.9 Å (Figure 4.5b). The patterns for the LiBF4 and NH4BF4 are virtually the same, supporting the assignment of the peak as due to inter-stack organization, which is not expected to show a metal dependence. Interestingly, additional peaks are observed in the XRD pattern of the NaBF4 sample, indicating that the columnar aggregates are more ordered with the incorporation of Na+, quite possibly the additional ordering only present upon solidification. It is hard to provide a definite explanation for this discrepancy, but perhaps the Na+ interacts with the interior of the macrocycles in a different way that facilitates improved order.  125  Figure 4.5. Powder XRD patterns of (a) macrocycles 42c–e with NH4BF4 and (b) macrocycle 42c with NH4BF4, LiBF4 and NaBF4.  126  Figure 4.6. Model of four molecules of macrocycle 42c with cation in the same plane; center-to-center distances to the middle macrocycle in the model are ca 28 Å apart. If each macrocycle represents an ion-induced tubular assembly of macrocycles, then this separation between the columns is reasonable.  4.3 Conclusions  In summary, unusual lyotropic LCs that form in non-polar solvents were discovered. These mesogens are formed by ion-induced tubular assemblies of a Schiff-base macrocycle/cation complex, where the stacks have a charged interior surrounded by hydrophobic alkyl substituents. The polyelectrolytic rod-shaped assemblies retain a  127  degree of orientational ordering in solution, leading to Nc lyotropic mesophases. This ion-induced assembly is reminiscent of the organization observed in self-assembled G-quartets with alkali metals,7a but, to the best of our knowledge, is unprecedented in macrocycle chemistry. Ion-induced assembly of macrocycles into lyotropic mesophases may be a useful design principle for constructing organized materials that can function as ion-conductors or as templates for nanostructures (for example, after cross-linking of polymerizable substituents on the macrocycles).5  4.4 Experimental  General Procedures: All reagents were used as received unless otherwise stated. Ammonium tetrafluoroborate, lithium tetrafluoroborate, sodium tetrafluoroborate and sodium tetraphenylborate were obtained from Aldrich. Chlorobenzene, HPLC grade chloroform and toluene were obtained from Fisher Scientific. The syntheses of [3+3] Schiff-base macrocycles 42c–e were carried out according to literature procedures.8  Equipment: An Olympus BX41 polarizing optical microscopy (POM) equipped with a digital camera was used to observe the textures of the lyotropic liquid crystals. The textures were identified by comparison with literature references and the book “Textures of Liquid Crystals”. 13 A good example of the “mesh” texture shown in Figures 4.2c,d has not been able to find, but it is believed that the texture is also from the nematic phase. Powder XRD data were recorded on a D8 Advance powder X-ray diffractometer by drop-casting the sample solutions onto silicon plates. IR spectra were obtained using a  128  Thermo Scientific Nicolet 6700 FT-IR spectrometer equipped with a diamond Attenuated Total Reflectance.  General Sample Preparation of Lyotropic Liquid Crystals for POM Imaging. Schiff-base macrocycle 42c–e (1.5 mg) was dissolved in chloroform (1 mL) and was mixed with an excess amount of ammonium or alkali metal salts (50 mg) for 5 sec to give a dark red solution. The solution was allowed to stand for 5 min before removing the excess salts by filtration through a Kimwipe pad. The dark red solution was then concentrated through evaporation before drop-casting onto the microscope glass slides for viewing under POM to observe the liquid crystalline textures.  Modelling: In order to determine the origin of the peak observed in the powder XRD patterns of the dried films, some rudimentary modellings were performed using Spartan ’04. A model macrocycle with extended dodecyloxy chains (i.e., macrocycle 42c) was constructed. It was assumed for the purpose of the modeling that each macrocycle was flat (in reality, the phenylenediamine moieties are probably nearly co-planar, but the catechols can rotate to orient above and below the plane), the centers representing the inter-columnar separation. Keeping one macrocycle fixed in place, three others were brought into close proximity. At a separation of ca. 28 Å, the molecules begin to overlap, but there is still considerable free space between them (see Figure 4.6). Assuming that the chains do not all lie in the same plane and are not necessarily fully extended, then there is sufficient space for the molecules to pack closer to one another, and the separation of 27 Å (measured by powder XRD) is reasonable for inter-columnar separation. With shorter chains as for macrocycles 42d and 42e, closer approach of the stacks is possible. 129  4.5 References  1.  (a) Stasiek, J. A.; Kowalewski, T. A. Opto-Electron. Rev. 2002, 10, 1. (b) Vejrazka, J.; Marty, P. Heat Transfer Eng. 2007, 28, 154. (c) Stasiek, J.; Stasiek, A.; Jewartowski, M.; Collins, M. W. Opt. Laser Technol. 2006, 38, 243. (d) Iles, A.; Fortt, R.; de Mello, A. J. Lab Chip 2005, 5, 540.  2.  (a) Hird, M. Chem. Soc. Rev. 2007, 36, 2070. (b) Kawamoto, H. Proc. IEEE 2002, 90, 460. (c) Gray, G. W.; Kelly, S. M. J. Mater. Chem. 1999, 9, 2037. (d) Toyooka, T.; Yoda, E.; Yamanashi, T.; Kobori, Y. Displays 1999, 20, 221.  3.  Hegmann, T.; Qi, H.; Marx, V. M. J. Inorg. Organomet. Polym. Mater. 2007, 17, 483.  4.  (a) Hulvat, J. F.; Sofos, M.; Tajima, K.; Stupp, S. I. J. Am. Chem. Soc. 2005, 127, 366. (b) Tschierske, C. J. Mater. Chem. 1998, 8, 1485. (c) Coppola, L.; Gianferri, R.; Nicotera, I.; Oliviero, C.; Ranieri, G. A. Phys. Chem. Chem. Phys. 2004, 6, 2364. (d) Nesrullajev, A.; Kazancı, N.; Yıldız, T. Mater. Chem. Phys. 2003, 80, 710. (e) Tracey, A. S.; Radley, K. Langmuir 1990, 6, 1221.  5.  Gin, D. L.; Pecinovsky, C. S.; Bara, J. E.; Kerr, R. L. Struct. Bond. 2008, 128, 181.  6.  Davis, J. T.; Spada, G. P. Chem. Soc. Rev. 2007, 36, 296.  7.  (a) Pieraccini, S.; Gottarelli, G.; Mariani, P.; Masiero, S.; Saturni, L.; Spada, G. P. Chirality 2001, 13, 7. (b) Giorgi, T.; Grepioni, F.; Manet, I.; Mariani, P.; Masiero, S.; Mezzina, E.; Pieraccini, S.; Saturni, L.; Spada, G. P.; Gottarelli, G. Chem. Eur. J. 2002, 8, 2143. (c) Kuang, G.-C.; Ji, Y.; Jia, X.-R.; Li, Y.; Chen, E.-Q.; Wei, Y.  130  Chem. Mater. 2008, 20, 4173. (d) Li, X.-Q.; Zhang, X.; Ghosh, S.; Würthner, F. Chem. Eur. J. 2008, 14, 8074. 8.  Gallant, A. J.; Hui, J. K.-H.; Zahariev, F. E.; Wang, Y. A.; MacLachlan, M. J. J. Org. Chem. 2005, 70, 7936.  9.  Hui, J. K.-H.; Frischmann, P. D. Tso, C.-H.; Michal, C. A.; MacLachlan, M. J. Chem. Eur. J. 2010, 16, 2453.  10. (a) Stackhouse, P. J.; Hird, M. Liq. Cryst. 2008, 35, 597. (b) Destrade, C.; Mondon, M. C.; Malthete, J. J. Phys. 1979, 40, C3. 11. Gallant, A. J.; MacLachlan, M. J. Angew. Chem. Int. Ed. 2003, 42, 5307. 12. (a) Ishi-i, T.; Hirashima, R.; Tsutsumi, N.; Amemori, S.; Matsuki, S.; Teshima, Y.; Kuwahara, R.; Mataka, S. J. Org. Chem. 2010, 75, 6858. (b) Petitjean, A.; Cuccia, L. A.; Schmutz, M.; Lehn, J.-M. J. Org. Chem. 2008, 73, 2481. (c) Liang, Y.; Jasbi, S. Z.; Haftchenary, S.; Morin, S.; Wilson, D. J. Biophys. Chem. 2009, 144, 1. 13. Dierking, I. Textures of Liquid Crystals; Wiley-VCH: Weinheim, 2003.  131  CHAPTER 5 SELF-ASSEMBLY OF ZINC(II) SALPHEN COMPLEXES INTO NANOFIBERS †  5.1 Introduction  The supramolecular self-assembly of molecules into one-dimensional nanostructures is an important goal for developing future nanoscale technologies, such as molecular circuitry and machines.1–5 Nanowires and nanotubes can be assembled using noncovalent interactions, including hydrogen-bonding and intermolecular π-π stacking.6–10 The formation of nanofibrils is also relevant to biological systems and diseases (for example, Alzheimer’s). 11 Moreover, there has been much recent interest in the gelation of fiber-forming assemblies. 12  In this chapter, the first examples of nanofiber formation promoted by Zn···O interactions between Schiff-base complexes 43 are presented (Figure 5.1). Such metal-ligand interactions between zinc and a phenolic oxygen have been reported as the basis of the reversible dimerization of [Zn(II)(salen)]-type complexes (salen = N,N′-bis(salicylidene)ethylenediamine). 13 , 14  These complexes dimerize to give a  five-coordinate metal center with the neighboring phenolic oxygen. Our group has †  A version of this chapter has been published as a communication: Hui, J. K.-H.; Yu, Z.; MacLachlan, M. J.  “Supramolecular Assembly of Zinc Salphen Complexes: Access to Metal-Containing Gels and Nanofibers” Angew. Chem. Int. Ed. 2007, 46, 7980.  132  ascribed the aggregation of large, zinc(II)-containing macrocycles in solution to Zn···O interactions. 15 Batley and Graddon proposed in 1967 that [Zn(II)(salen)] complexes could form polymeric structures, 16 but definitive evidence for aggregation has not been reported. This chapter presents a new family of zinc(II) salphen complexes that organize into one-dimensional nanofibers and their gelation phenomenon.  Figure 5.1. Chemical structure of zinc(II) salpen complexes 43.  5.2 Results and Discussion  A  series  of  zinc(II)  salphen  complexes  43  (salphen  =  N,N′-bis(salicylidene)-o-phenylenediamine) with peripheral linear and branched alkoxy groups were prepared. Surprisingly, complex 43a was discovered to form luminescent gels in methanol (ca. 3 mg mL-1), Figure 5.2. Gel formation was also observed in toluene, but not in DMF or chloroform. In gel-forming solvents, formation was thermoreversible, and could be readily disrupted with addition of pyridine (< 2%), which coordinates to the zinc center. Table 5.1 shows the gel-forming abilities of complexes 43a–e in various  133  solvents. Notably, the complexes form gels best in aromatic solvents, such as benzene, toluene, and o-xylene.  Figure 5.2. (a) Photograph of the gel of complex 43a in methanol under visible light (left) and when irradiated with UV light (right). (b) Fiber morphology of complex 43a cast from methanol, as observed by TEM.  134  Table 5.1. Gel forming abilities of complexes 43a–e in various solvents.a,b  43a  43b  43c  43d  43e  Methanol  Y  N  N  N  N  Ethanol  N  N  N  N  N  Toluene  Y  N  Y  Y  Y  Acetonitirle  N  N  N  N  N  Ethyl acetate  N  N  N  N  N  Benzene  Y  N  Y  Y  Y  Pyridine  N  N  N  N  N  o-Xylene  Y  N  Y  Y  Y  DMF  N  N  N  N  N  (a) Concentration = 3 mg mL-1. (b) Y = gel observed, N = no gel observed.  TEM revealed that complexes 43a–e all form fibers when cast from methanol (Figure 5.3). In each case, the fibers are only tens of nanometers in diameter but extend several microns in length. The relatively large diameters and rope morphology of the fibers suggest that they are not one molecule thick, but instead are formed from the assembly of one-dimensional fibers into bundles. Fiber formation was observed for chain lengths ranging from methoxy to hexadecyloxy.  135  Figure 5.3. TEM images of complexes (a) 43a, (b) 43b, (c) 43c, (d) 43e, and (e,f) 43d deposited from methanol.  The fibers on the TEM grids do not exhibit electron diffraction and were too small to study by XRD. Powder XRD studies of dried films of the zinc complexes cast from methanol do show some crystallinity. In the case of complex 43c, the diffraction pattern (Figure 5.4) fits to a tetragonal unit cell with a = b = 14.90 Å, c = 20.49 Å and α = β = γ =  136  90o. For the other complexes, an insufficient number of peaks was observed to determine the unit cell with confidence.  Figure 5.4. Powder XRD pattern of complex 43c.  The fiber morphology observed in the zinc(II) salphen complexes was initially thought to be a consequence of the hydrophobic alkoxy substituents on the salphen complexes, which lead the complexes to aggregate in methanol. It is hypothesized that replacing the alkoxy substituents of complexes 43a–e with hydrophilic substituents, such as monosaccharides, may disrupt the organization or may favor the formation of single-strand nanofibrils from methanol. To test this hypothesis, zinc(II) complexes 43f and 43g, functionalized with glucose and galactose, respectively, were prepared.  137  Drop-casting of complexes 43f and 43g from methanol, in which they are very soluble, mostly led to the formation of nanofibrils on the TEM grid (Figure 5.5). For both complexes, very narrow structures with diameters of about 5–7 nm, but with lengths that extend over micrometers, are formed. The fibers are all of similar width, and are much narrower than those from complexes 43a–e.  Figure 5.5. TEM images of complexes (a,b) 43f and (c,d) 43g deposited from methanol.  It is believed that the one-dimensional assembly observed for complexes 43a–g involves Zn···O interactions rather than hydrogen-bonding or π-π interactions between the salphen complexes. Although Zn···O interactions could not be observed directly, several model compounds (nickel(II) salphen complexes 54a–d, and zinc(II) salphen complexes  138  55 and 56, Figure 5.6) were made and carried out control experiments that support this assignment. The possibility that the zinc(II) salphen complexes dimerize then further assemble through π-π interactions cannot be ruled out. However, MALDI-TOF mass spectrometry studies of the fibers show the monomeric zinc complex rather than the dimer as the prevalent species. In addition, π-π interactions, which are frequently seen in polycyclic aromatics are ruled out, as the exclusive interaction, as square-planar nickel(II) complexes 54a–d do not show similar organization to the zinc(II) complexes. TEM images of the nickel(II) complexes show only ill-defined morphologies when cast from methanol or solvent mixtures (Figure 5.7). Complexes 43f and 43g with copper or vanadyl in the place of zinc also show no fiber assembly.  RO  OR  N  H29C14O  N  N  Ni O  OC14H29  N  H29C14O  N  Zn O  O  54a R = C14H29 54b R = CH3  N Zn  O  55  OC14H29  S  S  56  OH O  54c R = HO HO  HO  HOOH O  54d R = HO  HO  Figure 5.6. Chemical structures of nickel(II) salphen complexes 54a–d, and zinc(II) salphen complexes 55 and 56.  139  Figure 5.7. TEM images of nickel(II) complexes (a) 54a, (b) 54b deposited from methanol/tetrahydrofuran and (c) 54c, (d) 54d deposited from methanol.  Complex 55 has bulky tert-butyl groups that should inhibit aggregation of the zinc(II) complexes. Indeed complex 55 does not form a gel in methanol or in toluene, and TEM images of this complex cast from methanol showed no fibrillar texture. Complex 56, which is the thiol analogue to complex 43a, does not self-assemble into fibers in methanol. In this case, the aggregation is most likely inhibited by the bulky sulfur atoms at the zinc center that prevent expansion of the coordination sphere of the metal center. Additionally, the softer sulfur atom would be expected to interact less strongly with zinc than oxygen. These control compounds further support that the aggregation is mediated at the metal center.  140  The UV-vis spectra for films of zinc(II) complexes 43a–g exhibit small red-shifts and broadening relative to the solution-phase spectra (see Figure 5.8 for an example of the spectrum with complex 43a). Moreover, the complexes are all luminescent, emitting at 525–540 nm, red-shifted by 20 nm from the solution phase. The similarity of the absorption and emission spectra for solutions and films of complexes 43a–g indicates that a similar aggregation mechanism is involved in both the assembly of alkoxy- and carbohydrate-substituted complexes.  Figure 5.8. UV-vis and fluorescence spectroscopy of complex 43a in methylene chloride and in the solid state (gel).  141  Further evidence for aggregation was obtained from ESI mass spectra of the complexes. All the spectra of the zinc complexes showed the molecular ion, but also showed peaks corresponding to aggregates. In fact, when the instrument was optimized for measurements on complex 43c, singly and doubly charged species up to nine monomers were able to observe (Figure 5.9). Although quantifying the individual species by ESI mass spectrometry is not feasible, the technique is known to give a snapshot of species present in solution. Thus, large aggregates of complex 43c are formed in solution, supporting the strong tendency of these complexes to aggregate.  Figure 5.9. ESI mass spectrum of complex 43c exhibits singly (red) and doubly (blue) charged species. A: [43c+Na]+, B: [43c2+Na]+, C: [43c3+Na]+, D: [43c4+Na]+, E: [43c5+Na]+, F: [43c3+Na2]2+, G: [43c5+Na2]2+, H: [43c7+Na2]2+, I: [43c9+Na2]2+. 142  Semi-empirical (PM3) calculations were performed to better understand the supramolecular organization in these structures. Assuming the zinc(II) center is five-coordinate in the fibers as observed in dimers of [Zn(salphen)]-type complexes, an oligomer containing seven unsubstituted zinc(II) salphen units was constructed and its energy minimized, starting from several different conformations. Figure 5.9 shows an energy minimized structure for the one-dimensional heptamer with five-coordinate zinc ions. Calculated Zn-O and Zn-N distances are in agreement with crystallographic studies of dimers. The polymeric backbone contains a (ZnO)n polymer as illustrated in Figure 5.10, with an insulating organic sheath.  Figure 5.10. Energy-minimized (PM3) calculated structure for a heptamer of zinc(II) salphen complex. (a) The entire oligomer containing seven zinc(II) salphen molecules connected into a one-dimensional structure. (b) An expanded view of three zinc(II) salphen complexes from the middle of the heptamer. (Color legend: carbon = green, nitrogen = blue, oxygen = red, zinc = grey) 143  An interesting revelation from the modelling is that the complexes assembled in the one-dimensional structures will likely assume a helical conformation. Regions of fibers of the zinc(II) complexes 43a–e appear to have helical structure, and it is possible this motif derives from the helical conformation of the polymer strand. Figures 5.3e,f show regions of fibers formed from complex 43d. In these images, there are segments that appear to have helical organization that may arise from the stacking of the salphen moieties.  It is noteworthy that the aggregation behavior observed for metal salphen complexes is distinct from that of porphyrins.10,17 Although porphyrins (and phthalocyanines) are also known to aggregate, their assembly is dominated by π-π stacking or interactions of substituents, and the metal dependence is generally less pronounced. As an example, Shinkai  and  co-workers  have  observed  improved  gelation  properties  of  a  copper-containing porphyrin over the analogous zinc(II)-containing porphyrin and have attributed this improvement to the stabilization of H-aggregates.17 The coordination environment of salphen complexes is much more flexible than that of porphyrin complexes, offering new possibilities for self-assembly  5.3 Conclusions  The first supramolecular assembly of zinc(II) salphen complexes into luminescent metal-organic gels and one-dimensional nanofibers was demonstrated. This work demonstrates the potential of reversible Zn···O interactions for self-assembly of  144  nanostructures. Structural changes to the side groups enable control over the morphology and dimensions of the nanofibers. Supramolecular assembly of salphen complexes may be used for the controlled organization of nanoscale patterns and wires, and the carbohydrate shell may ultimately prove beneficial for biological integration. Our interest on modifying the morphology of the fibrous structure with carbohydrate-appended zinc(II) salphen complexes and metallosalphen with dinuclear zinc(II) centers will be discussed in the next two chapters.  5.4 Experimental  General Procedures: All reactions were carried out under nitrogen atmosphere by means of standard Schlenk techniques unless otherwise stated. Tetrahydrofuran was distilled from sodium/benzophenone under nitrogen. Methylene chloride was dried by passage over alumina columns. Acetonitrile, methanol, and triethylamine were purged with nitrogen gas and dried over molecular sieve before use. Deuterated solvents were obtained from Cambridge Isotope Laboratories, Inc.. All reagents were used as received unless  otherwise  stated.  Penta-O-acetyl-α-D-glucopyranose,  penta-O-acetyl-β-D-glucopyranose, hydrobromic acid (48% in water), hydrobromic acid (30%  in  acetic  acid),  veratrole,  3,5-di(tert-butyl)-2-hydroxybenzaldehyde,  ammonium  formate,  salicylaldehyde,  nickel(II)  acetylacetonate,  zinc(II)  acetylacetonate, nickel(II) acetate, zinc(II) acetate dihydrate, and sodium methoxide were obtained from Aldrich. Silver(I) oxide was obtained from Strem. Palladium on carbon was obtained from Pressure Chemical. Nitric acid was obtained from Fisher.  145  4,5-Bis(hexyloxy)phenylenediamine (46c),18  (46a),18  4,5-bis(tetradecyloxy)phenylenediamine (46d),18  4,5-dimethoxyphenylenediamine  4,5-bis(2-ethylhexyloxy)phenylenediamine  (46e),18  4,5-bis(hexadecyloxy)phenylenediamine  (46f),18  4,5-bis(tetra-O-acetyl-β-D-glucopyranosyl)phenylenediamine  (46g),19  4,5-bis(tetra-O-acetyl-β-D-galactopyranosyl)phenylenediamine  (46h)19  and  (S)-(2-formylphenyl)dimethylthiocarbamate (57)20 were prepared by literature methods.  Equipment: 300 MHz 1H and 75.5 MHz  13  C NMR spectra were recorded on a Bruker  AV-300 spectrometer. 400 MHz 1H and 100.6 MHz 13C NMR spectra were recorded on a Bruker AV-400 spectrometer. UV-vis spectra were performed in methylene chloride and methanol on a Varian Cary 5000 UV-vis/near-IR spectrometer using a 1 cm cuvette. Solid-state UV-vis spectra were obtained by drop-casting the methanol solutions of the complexes onto microscope slides. Mass spectra and elemental analyses were obtained at the UBC Microanalytical Services Laboratory. MALDI mass spectra were obtained on a Bruker Biflex IV TOF mass spectrometer equipped with a MALDI ion source. ESI mass spectra were obtained on a Micromass LCT TOF mass spectrometer equipped with an electrospray ion source. Samples were analyzed in methanol/methylene chloride at 1 μM. Electron Impact (EI) mass spectra were recorded on a Kratos MS-50 double focusing sector mass spectrometer equipped with an EI ion source. Melting points were obtained on a Fisher-John’s melting point apparatus. TEM images were obtained at the UBC BioImaging Facility on a Hitachi H7600 transmission electron microscope. Samples were prepared by dissolving the complexes in methanol or methanol/tetrahydrofuran mixture and drop-cast onto carbon-coated grids. Powder XRD data were recorded on a D8 146  Advance powder X-ray diffractometer by drop-casting the methanol solutions of the complexes onto silicon plates. Powder XRD patterns were indexed with Crysfire. Calculations were performed using Spartan ’04 for Windows (Wavefunction, Inc.). Initially, a trimer was prepared and was minimized from a variety of conformations. This was then expanded to a heptamer, and the energy of the heptamer was minimized. Stable conformations were produced, and the one shown in Figure 5.10 was the lowest of several attempts; it is not the global minimum, but a stable conformation of the oligomer. Figure 5.10 was prepared using Pymol.21  Synthesis of Zinc(II) Salphen Complex 43a. 4,5-Bis(tetradecyloxy)phenylenediamine (46c) (0.300 g, 0.563 mmol) was dissolved in tetrahydrofuran (60 mL) under nitrogen. Salicylaldehyde (0.130 mL, 1.24 mmol) and zinc(II) acetate dihydrate (0.185g, 0.844 mmol) were added, giving a yellow solution. The solution was stirred at reflux (90 oC) for 24 h. After cooling to room temperature, the solvent was removed by rotary evaporation to give a yellow solid. The solid was redissolved in a minimum amount of methylene chloride and precipitated into methanol. After the crude product was isolated by filtration, it was recrystallized from methylene chloride/methanol mixture to yield complex 43a (0.409 g, 90%, yellow solid).  Data for Zinc(II) Salphen Complex 43a. 1H NMR (400 MHz, DMSO-d6) δ 8.95 (s, 2H, CH=N), 7.47 (s, 2H, aromatic CH), 7.41 (d, 2H, aromatic CH), 7.21 (t, 2H, aromatic CH), 6.69 (d, 2H, aromatic CH), 6.50 (t, 2H, aromatic CH), 4.10 (t, 4H, OCH2), 1.76 (quintet, 4H, CH2), 1.48 (quintet, 4H, CH2), 1.23 (broad, 40H, CH2), 0.84 (t, 6H, CH3) ppm.  13  C  NMR (75.5 MHz, chloroform-d1) δ 171.5 (CH=N), 159.2, 149.2, 135.2, 133.7, 132.7, 147  123.8, 119.3, 113.6, 100.3 (aromatic C), 69.5, 31.7, 29.5, 29.2, 29.1, 25.8, 22.4 (CH2), 13.9 (CH3) ppm. MALDI-TOF-MS: m/z = 803.3 ((M+H)+). UV-vis (methylene chloride): λmax (ε) = 247 (3.11x104), 298 (2.74x104), 390 (3.17x104) nm (cm-1 mol-1 L). UV-vis (solid): λmax = 298, 407 nm. Fluorescence (methylene chloride): λmax = 518 nm, λexc = 390 nm; Fluorescence (solid): λmax = 538 nm, λexc = 407 nm. Anal. Calc’d (%) for 43a (C48H70N2O4Zn): C 71.66, H 8.77, N 3.48; Found: C 71.71, H 8.71, N 3.50. m.p. = 130–132 oC.  Synthesis of Zinc(II) Salphen Complex 43b. Complex 43b (91%, yellow solid) was prepared by the same procedure and purification as for complex 43a.  Data for Zinc(II) Salphen Complex 43b. 1H NMR (400 MHz, DMSO-d6) δ 8.99 (s, 2H, CH=N), 7.49 (s, 2H, aromatic CH), 7.42 (d, 2H, aromatic CH), 7.22 (t, 2H, aromatic CH), 6.70 (d, 2H, aromatic CH), 6.51 (t, 2H, aromatic CH), 3.92 (s, 6H, OCH3) ppm. 13C NMR (100.6 MHz, DMSO-d6) δ 171.7 (CH=N), 160.6, 148.9, 135.7, 133.7, 132.6, 122.8, 119.6, 112.8, 99.6 (aromatic C), 56.1 (OCH3) ppm. MALDI-TOF-MS: m/z = 439.4 ((M+H)+). UV-vis (methanol): λmax (ε) = 243 (3.21x104), 297 (2.86x104), 333 (1.87x104), 350 (2.31x104), 393(3.59x104), 433 (2.14x104) nm (cm-1 mol-1 L). UV-vis (solid): λmax = 264, 302, 406 nm. Fluorescence (methanol): λmax = 522 nm, λexc = 393 nm. Fluorescence (solid): λmax = 563 nm, λexc = 406 nm. Anal. Calc’d (%) for 43b (C22H18N2O4Zn): C 60.08, H 4.13, N 6.37; Found: C 57.05, H 4.66, N 6.71. m.p. = did not melt at 300 oC.  Synthesis of Zinc(II) Salphen Complex 43c. Complex 43c (85%, yellow solid) was prepared by the same procedure and purification as for complex 43a. 148  Data for Zinc(II) Salphen Complex 43c. 1H NMR (300 MHz, DMSO-d6) δ 8.97 (s, 2H, CH=N), 7.48 (s, 2H, aromatic CH), 7.43 (d, 2H, aromatic CH), 7.21 (t, 2H, aromatic CH), 6.70 (d, 2H, aromatic CH), 6.51 (t, 2H, aromatic CH), 4.11 (t, 4H, OCH2), 1.76 (broad, 4H, CH2), 1.48 (broad, 4H, CH2), 1.34 (broad, 8H, CH2), 0.90 (t, 6H, CH3) ppm.  13  C  NMR (100.6 MHz, DMSO-d6) δ 171.7 (CH=N), 160.7, 148.8, 135.8, 133.7, 132.8, 122.9, 119.7, 112.8, 101.1 (aromatic C), 68.8, 31.0, 28.8, 25.3, 22.1 (CH2), 13.9 (CH3) ppm. MALDI-TOF-MS: m/z = 578.7 ((M+H)+). UV-vis (methanol): λmax (ε) = 243 (3.37x104), 298 (3.03x104), 351 (2.35x104), 393 (4.02x104) nm (cm-1mol-1 L). UV-vis (solid): λmax = 306, 416 nm. Fluorescence (methanol): λmax = 518 nm, λexc = 393 nm. Fluorescence (solid): λmax = 543 nm, λexc = 416 nm. Anal. Calc’d (%) for 43c·H2O (C32H40N2O5Zn): C 64.26, H 6.74, N 4.68; Found: C 64.06, H 6.70, N 4.67. m.p. = 224–226 oC.  Synthesis of Zinc(II) Salphen Complex 43d. Complex 43d (97%, yellow solid) was prepared by the same procedure and purification as for complex 43a.  Data for Zinc(II) Salphen Complex 43d. 1H NMR (400 MHz, DMSO-d6) δ 8.96 (s, 2H, CH=N), 7.47 (s, 2H, aromatic CH), 7.43 (d, 2H, aromatic CH), 7.21 (t, 2H, aromatic CH), 6.69 (d, 2H, aromatic CH), 6.51 (t, 2H, aromatic CH), 4.01 (d, 4H, OCH2), 1.72 (broad, 2H, CH2), 1.51 (m, 8H, CH2), 1.34 (broad, 8H, CH2), 0.84 (m, 12H, CH3) ppm. 13C NMR (100.6 MHz, DMSO-d6) δ 171.6 (CH=N), 160.5, 149.0, 135.8, 133.6, 132.7, 122.9, 119.6, 112.7, 100.6 (aromatic C), 70.9, 30.2, 28.6, 23.5, 22.5 (CH2), 13.9, 11.2 (CH3) ppm. MALDI-TOF-MS: m/z = 635.8 ((M+H)+). UV-vis (methanol): λmax (ε) = 243 (3.84x104), 299 (3.47x104), 352 (2.74x104), 393 (4.65x104) nm (cm-1 mol-1 L). UV-vis (solid): λmax = 273, 303, 417 nm. Fluorescence (methanol): λmax = 518 nm, λexc = 393 nm. Fluorescence 149  (solid): λmax = 544 nm, λexc = 417 nm. Anal. Calc’d (%) for 43d·H2O (C36H48N2O5Zn): C 66.10, H 7.40, N 4.28; Found: C 66.09, H 7.39, N 4.67. m.p. = 289–291 oC.  Synthesis of Zinc(II) Salphen Complex 43e. Complex 43e (79%, brownish yellow solid) was prepared by the same procedure and purification as for complex 43a. Data for Zinc(II) Salphen Complex 43e. 1H NMR (400 MHz, DMSO-d6) δ 8.95 (s, 2H, CH=N), 7.47 (s, 2H, aromatic CH), 7.42 (s, 2H, aromatic CH), 7.20 (broad, 2H, aromatic CH), 6.69 (d, 2H, aromatic CH), 6.50 (broad, 2H, aromatic CH), 4.11 (broad, 4H, OCH2), 1.76 (broad, 4H, CH2), 1.47 (broad, 4H, CH2), 1.24 (broad, 48H, CH2), 0.85 (broad, 6H, CH3) ppm.  13  C NMR (100.6 MHz, DMSO-d6) δ 171.5 (CH=N), 160.1, 148.8, 135.5,  133.3, 132.6, 122.9, 119.4, 112.7, 100.8 (aromatic C), 68.9, 31.2, 29.1, 29.0, 29.0, 29.0, 29.0, 29.1, 28.8, 28.8, 28.7, 25.6, 22.0 (CH2), 13.7 (CH3) ppm. MALDI-TOF-MS: m/z = 859.7 ((M+H)+). UV-vis (methanol): λmax (ε) = 243 (2.23x104), 298 (2.02x104), 351 (1.54x104), 393 (2.66x104) nm (cm-1 mol-1 L). UV-vis (solid): λmax = 298, 409 nm. Fluorescence (methanol): λmax = 519 nm, λexc = 393 nm. Fluorescence (solid): λmax = 543 nm, λexc = 409 nm. Anal. Calc’d (%) for 43e·H2O (C52H80N2O5Zn): C 71.09, H 9.18, N 3.19; Found: C 71.21, H 9.12, N 3.37. m.p. = 114–117 oC.  Synthesis of Zinc(II) Salphen Complex 43f. Salicylaldehyde (0.086 mL, 0.824 mmol) and zinc(II) acetylacetonate (0.148 g, 0.562 mmol) were added to a solution of 4,5-bis(tetra-O-acetyl-β-D-glucopyranosyl)phenylenediamine 46g (0.300 g, 0.375 mmol) in tetrahydrofuran (40 mL). The yellow solution was stirred at 50oC for 24 h. After cooling down to room temperature, the crude product was isolated by precipitation with petroleum ether then filtration. It was then purified by chromatography on silica gel 150  (ethyl acetate) and yielded the intermediate acetyl-protected glucose-functionalized zinc(II) salphen complex. Triethylamine (30 mL) was added to a solution of the intermediate zinc(II) salphen complex in methanol (50 mL). The yellow solution was stirred at room temperature for 24 h. The solvent was then removed by rotary evaporation to obtain a yellow solid. The crude product was dissolved in methanol and re-precipitated with petroleum ether, followed by filtration to yield salphen complex 43f (0.083 g, 30%, yellow solid).  Data for Zinc(II) Salphen Complex 43f. 1H NMR (300 MHz, DMSO-d6) δ 8.87 (s, 2H, CH=N), 7.71 (s, 2H, aromatic CH), 7.36 (d, 2H, aromatic CH), 7.23 (t, 2H, aromatic CH), 6.70 (d, 2H, aromatic CH), 6.50 (t, 2H, aromatic CH), 5.28 (s, 2H, CH), 5.17 (s, 2H, CH), 5.12 (d, 2H, CH), 4.97 (d, 2H, CH), 4.88 (t, 2H, CH), 3.77 (m, 2H, CH), 3.48 (broad, 8H, OH), 3.21 (m, 2H, CH) ppm. 13C NMR (100.6 MHz, DMSO-d6) δ 171.9 (CH=N), 161.4, 146.9, 136.1, 134.1, 134.0, 123.0, 119.6, 112.9, 105.2 (aromatic C), 101.6, 77.5, 76.6, 73.4, 70.3, 61.1 (CH) ppm. MALDI-TOF-MS: m/z = 734.6 ((M+H)+). UV-vis (methanol): λmax (ε) = 242 (2.75x104), 297 (2.49x104), 342 (1.66x104), 394 (2.68x104) nm (cm-1 mol-1 L). UV-vis (solid): λmax = 296 nm, 404 nm. Fluorescence (methanol): λmax = 507 nm, λexc = 394 nm. Fluorescence (solid): λmax = 527 nm, λexc = 404 nm. Anal. Calc’d (%) for 43f·2H2O (C32H38N2O16Zn): C 49.78, H 4.96, N 3.63; Found: C 45.14, H 4.65, N 3.22. m.p. = 249–252 oC (decomposed at 242 oC).  Synthesis of Zinc(II) Salphen Complex 43g. Complex 43g (38%, yellow solid) was prepared by the same procedure and purification as for complex 43f. The intermediate  151  zinc(II) salphen complex was purified by chromatography on silica gel (95:5 ethyl acetate/acetone).  Data for Zinc(II) Salphen Complex 43g. 1H NMR (400 MHz, DMSO-d6) δ 8.86 (s, 2H, CH=N), 7.73 (s, 2H, aromatic CH), 7.36 (d, 2H, aromatic CH), 7.22 (t, 2H, aromatic CH), 6.70 (d, 2H, aromatic CH), 6.49 (t, 2H, aromatic CH), 5.15 (s, 2H, CH), 4.92 (t, 6H, CH), 4.61 (s, 2H, CH), 3.69 (s, 4H, CH), 3.59 (broad, 4H, OH), 3.45 (broad, 4H, OH) ppm. 13C NMR (75.5 MHz, DMSO-d6) δ 171.9 (CH=N), 161.2, 147.0, 136.0, 134.0, 133.9, 122.9, 119.5, 112.8, 105.2 (aromatic C), 102.2, 76.1, 73.2, 70.4, 68.5, 60.9 (CH) ppm. MALDI-TOF-MS: m/z = 735.1 ((M+H)+); UV-vis (methanol): λmax (ε) = 242 (2.33x104), 297 (1.82x104), 343 (1.23x104), 395 (1.97x104) nm (cm-1 mol-1 L). UV-vis (solid): λmax = 291 nm, 395 nm. Fluorescence (methanol): λmax = 506 nm, λexc = 395 nm. Fluorescence (solid): λmax = 525 nm, λexc = 395 nm; Anal. Calc’d (%) for 43g·H2O (C32H36N2O15Zn): C 50.97, H 4.81, N 3.72; Found: C 46.75, H 4.95, N 3.92; m.p. = 253–256 oC (decomposition started at 240 oC).  Synthesis of Nickel(II) Salphen Complex 54a. Salicylaldehyde (0.130 mL, 1.24 mmol) and nickel(II) acetate (0.210g, 0.844 mmol) were added to a solution of 4,5-bis(tetradecyloxy)phenylenediamine (46c) (0.300 g, 0.563 mmol) in 60 mL of tetrahydrofuran all under nitrogen. The dark red solution was stirred at reflux (90 oC) for 24 h. After cooling to room temperature, the solvent was removed by rotary evaporation to give a red solid. The solid was dissolved in a minimum amount of methylene chloride and precipitated into methanol to remove acetic acid and excess reagents. The product  152  was isolated by filtration and dried under vacuum. Complex 54a (0.421 g, 94%) was isolated as a red solid.  Data for Nickel(II) Salphen Complex 54a. 1H NMR (400 MHz, methylene chloride-d2) δ 8.00 (s, 2H, CH=N), 7.34 (d, 2H, aromatic CH), 7.26 (t, 2H, aromatic CH), 7.09 (s, 2H, aromatic CH), 6.95 (d, 2H, aromatic CH), 6.62 (t, 2H, aromatic CH), 3.99 (t, 4H, OCH2), 1.80 (q, 4H, CH2), 1.56 (s, 4H, CH2), 1.28 (broad, 40H, CH2), 0.88 (t, 6H, CH3) ppm. 13C NMR (75.5 MHz, methylene chloride-d2) δ 166.0 (CH=N), 153.1, 150.2, 136.5, 135.4, 133.8, 121.5, 120.7, 116.1 (aromatic C), 70.3 (OCH2), 32.5, 30.3, 30.2, 30.0, 29.9, 29.8, 26.6, 23.3 (CH2), 14.4 (CH3) ppm. MALDI-TOF-MS: m/z = 797.3 ((M+H)+). UV-vis (methylene chloride): λmax (ε) = 261 (4.70x104), 298 (1.94x104), 383 (3.84x104), 483 (1.33x104) nm (cm-1 mol-1 L). Anal. Calc’d (%) for 54a (C48H70N2NiO4): C 72.27, H 8.84, N 3.51; Found: C 72.65, H 8.76, N 3.49. m.p. = 126–128 oC.  Synthesis of Nickel(II) Salphen Complex 54b. Salicylaldehyde (0.411 mL, 3.92 mmol) and nickel(II) acetate (0.666 g, 2.68 mmol) were added to a solution of 4,5-dimethoxyphenylenediamine (46d) (0.300 g, 1.78 mmol) in 50 mL of tetrahydrofuran under nitrogen. The deep red solution was stirred at reflux (90 oC) for 24 h, and some red precipitate was observed after stirring for several hours. After the reaction was cooled to room temperature, the crude product was precipitated out by adding water to the red solution, then isolated by filtration. The crude product was recrystallized from methylene chloride/methanol to obtain complex 54b (0.730 g, 95%, red solid).  153  Data for Nickel(II) Salphen Complex 54b. 1H NMR (400 MHz, DMSO-d6) δ 8.69 (s, 2H, CH=N), 7.64 (s, 2H, aromatic CH), 7.57 (d, 2H, aromatic CH), 7.28 (t, 2H, aromatic CH), 6.87 (d, 2H, aromatic CH), 6.65 (t, 2H, aromatic CH), 3.88 (s, 6H, OCH3) ppm. 13C NMR (100.6 MHz, DMSO-d6) δ 164.4 (CH=N), 154.6, 149.2, 135.6, 134.5, 133.7, 120.4, 120.0, 115.0, 98.5 (aromatic C), 56.2 (OCH3) ppm. MALDI-TOF-MS: m/z = 433.4 ((M+H)+). UV-vis (methylene chloride): λmax (ε) = 261 (5.77x104), 297 (2.36x104), 383 (4.66x104), 484 (1.58x104) nm (cm-1 mol-1 L). Anal. Calc’d (%) for 54b (C22H18N2NiO4): C 61.01, H 4.19, N 6.47; Found: C 60.51, H 4.46, N 6.84. m.p. = did not melt at 300 oC.  Synthesis  of  Nickel(II)  Salphen  Complex  54c.  4,5-Bis(tetra-O-acetyl-β-D-glucopyranosyl)phenylenediamine 46g (0.300 g, 0.375 mmol) was dissolved in tetrahydrofuran (40 mL) under nitrogen. Salicylaldehyde (0.086 mL, 0.824 mmol) and nickel(II) acetylacetonate (0.14 g, 0.562 mmol) were then added, giving a dark red solution. The solution was stirred at 50 oC for 24 h. After cooling to room temperature, petroleum ether was added to the flask to precipitate the crude product solid, which was isolated by filtration. Chromatography on silica gel (3:1 methylene chloride/ethyl acetate) yielded the intermediate acetyl-protected glucose-functionalized nickel(II) salphen complex. The intermediate nickel(II) salphen complex was dissolved in 120 mL of methanol, giving a red solution. Sodium methoxide (0.122 g, 2.26 mmol) was added and the reaction was stirred at room temperature for 24 h. Orange precipitate was observed after stirring for several hours. The orange solid was filtered and yielded complex 54c (0.164 g, 60%, orange solid).  154  Data for Nickel(II) Salphen Complex 54c. 1H NMR (400 MHz, DMSO-d6) δ 8.57 (s, 2H, CH=N), 7.88 (s, 2H, aromatic CH), 7.51 (d, 2H, aromatic CH), 7.31 (t, 2H, aromatic CH), 6.88 (d, 2H, aromatic CH), 6.66 (t, 2H, aromatic CH), 5.30 (s, 2H, CH), 5.13 (d, 4H, CH), 4.97 (d, 2H, CH), 4.88 (t, 2H, CH), 3.48 (broad, 8H,OH) 3.78 (m, 2H, CH), 3.16 (m, 2H, CH) ppm. 13C NMR (100.6 MHz, DMSO-d6) δ 164.8 (CH=N), 155.2, 147.0, 136.7, 135.0, 134.1, 120.3, 120.2, 115.3, 104.2 (aromatic C), 101.4, 77.5, 76.7, 73.3, 70.2, 61.0 (CH) ppm. MALDI-TOF-MS: m/z = 729.5 ((M+H)+). UV-vis (methanol): λmax (ε) = 228 (3.50x104), 255 (3.97x104), 292 (2.27x104), 375 (3.08x104), 470 (1.63x104) nm (cm-1 mol-1 L). Anal. Calc’d (%) for 54c (C32H34N2NiO14): C 52.70, H 4.70, N 3.84; Found: C 48.70, H 4.68, N 3.75. m.p. = 244–247 oC (decomposition started at 240 oC).  Synthesis of Nickel(II) Salphen Complex 54d. Complex 54d (20%, red solid) was prepared by the same procedure and purification as for complex 43f. The intermediate nickel(II) salphen complex was purified by chromatography on silica gel (3:1 methylene chloride/ethyl acetate).  Data for Nickel(II) Salphen Complex 54d. 1H NMR (400 MHz, DMSO-d6) δ 8.58 (s, 2H, CH=N), 7.93 (s, 2H, aromatic CH), 7.52 (d, 2H, aromatic CH), 7.31 (t, 2H, aromatic CH), 6.88 (d, 2H, aromatic CH), 6.66 (t, 2H, aromatic CH), 5.19 (broad, 2H, CH), 4.94 (d, 6H, CH), 4.62 (broad, 2H, CH), 3.71 (s, 4H, CH), 3.67 (broad, 4H, OH), 3.58 (broad, 4H, OH) ppm. 13C NMR (100.6 MHz, DMSO-d6) δ 164.8 (CH=N), 155.2, 147.2, 136.7, 135.0, 134.1, 120.3, 120.2, 115.2, 104.4 (aromatic C), 102.1, 76.2, 73.4, 70.4, 68.5, 60.4 (CH) ppm. MALDI-TOF-MS: m/z = 729.1 ((M+H)+). UV-vis (methanol): λmax (ε) = 228 (1.97x104), 255 (2.32x104), 294 (1.08x104), 374 (1.74x104), 468 (6.60x103) nm (cm-1 155  mol-1 L). Anal. Calc’d (%) for 54d (C32H34N2NiO14): C 52.7, H 4.70, N 3.84; Found: C 46.03, H 4.41, N 3.68. m.p. = 241–243 oC (decomposition started at 236 oC).  Synthesis of Zinc(II) Salphen Complex 55. Complex 55 (68%, orange solid) was prepared by the same procedure as for complex 43a. It was purified by recrystallization from methylene chloride.  Data for Zinc(II) Salphen Complex 55. 1H NMR (400 MHz, DMSO-d6) δ 8.92 (s, 2H, CH=N), 7.48 (s, 2H, aromatic CH), 7.27 (s, 2H, aromatic CH), 7.23 (s, 2H, aromatic CH), 4.11 (t, 4H, OCH2), 1.76 (broad, 4H, CH2), 1.48 (broad, 4H, CH2), 1.48 (broad, 18H, CH3),1.29 (broad, 18H, CH3), 1.24 (broad, 40H, CH2), 0.85 (t, 6H, CH3) ppm. 13C NMR (100.6 MHz, DMSO-d6) δ 169.6 (CH=N), 160.4, 148.4, 140.5, 132.9, 129.1, 127.6, 118.2, 100.8 (aromatic C), 68.8 (OCH2), 35.1, 33.5 (CCH3), 31.4 (CCH3), 31.2 (CH2), 29.5 (CCH3), 29.1, 29.0, 28.9, 28.8, 28.8, 28.7, 25.7, 22.0 (CH2), 13.8 (CH3) ppm. MALDI-TOF-MS: m/z = 1028.1 ((M+H)+). UV-vis (methanol): λmax (ε) = 251 (3.77x104), 304 (3.13x104), 340 (2.12x104), 361 (2.21x104), 417 (3.85x104) nm (cm-1 mol-1 L). Fluorescence (methanol): λmax = 535 nm, λexc = 417 nm. Anal. Calc’d (%) for 55 (C64H102N2O4Zn): C 74.71, H 9.99, N 2.72; Found: C 74.46, H 10.19, N 3.07. m.p. = 119–121 oC.  Synthesis of Zinc(II) Salphen Complex 56. Sodium hydroxide (57.3 mg, 1.43 mmol) was  added  to  an  isopropanol  solution  (50  mL)  of  (S)-(2-formylphenyl)dimethylthiocarbamate (57, Scheme 5.1) (0.300 g, 1.43 mmol) under nitrogen. The resulting orange solution was then stirred at reflux (110 oC) for 5 h. 156  4,5-Bis(tetradecyloxy)phenylenediamine (46c) (0.306 g, 0.574 mmol) was dissolved in isopropanol (20 mL) under nitrogen and was then transferred to a reaction flask, followed by the addition of zinc(II) acetate dihydrate (0.215g, 0.979 mmol), giving an orange solution. The solution was stirred at reflux for 24 h. After cooling to room temperature, water was added and the product was extracted into methylene chloride. The solvent was removed by rotary evaporation to give a red solid that was recrystallized from a mixture of methylene chloride and methanol, yielding brown solid and was then isolated by filtration. The brown solid was further purified by flushing through a pad of silica gel with ethyl acetate, followed by recrystallization with a mixture of methylene chloride and methanol, yielding salphen complex 56 (0.144 g, 30%, brownish yellow solid).  H29C14O  OC14H29  O 2.5  1) 2.5 NaOH, i-PrOH S N O  2) H29C14O  OC14H29  N  N Zn  S  57  S  56 H2N  NH2  46c 1.7 Zn(OAc)2.2H2O, i-PrOH  Scheme 5.1. Synthesis of zinc(II) salphen complex 56.  Data for Zinc(II) Salphen Complex 56. 1H NMR (400 MHz, DMSO-d6) δ 9.01 (s, 2H, CH=N), 7.60 (d, 2H, aromatic CH), 7.44 (d, 2H, aromatic CH), 7.43 (s, 2H, aromatic CH), 7.13 (t, 2H, aromatic CH), 7.02 (t, 2H, aromatic CH), 4.13 (t, 4H, OCH2), 1.76 (broad, 4H, CH2), 1.48 (broad, 4H, CH2), 1.24 (broad, 40H, CH2), 0.85 (t, 6H, CH3) ppm. 157  MALDI-TOF-MS: m/z = 836.2 ((M+H)+). UV-vis (methanol): λmax (ε) = 264 (1.40x104), 313 (9.06x104), 361 (8.95x103) nm (cm-1 mol-1 L). Fluorescence (methanol): λmax = 431 nm, λexc = 361 nm. Anal. Calc’d (%) for 56·H2O (C48H72N2O3S2Zn): C 67.46, H 8.49, N 3.28; Found: C 68.09, H 8.66, N 3.59. m.p. = 153–155 oC.  158  5.5 References  1.  Grave, C.; Schlüter, A. D. Eur. J. Org. Chem. 2002, 3075.  2.  Yamaguchi, Y.; Yoshida, Z.-i. Chem. Eur. J. 2003, 9, 5430.  3.  Moore, J. S. Acc. Chem. Res. 1997, 30, 402.  4.  Iijima, S. Nature 1991, 354, 56.  5.  Morales, A. M.; Lieber, C. M. Science 1998, 279, 208.  6.  (a) Tamaru, S.-i. ; Nakamura, M.; Takeuchi, M.; Shinkai, S. Org. Lett. 2001, 3, 3631. (b) Tamaru, S.-i.; Takeuchi, M.; Sano, M.; Shinkai, S. Angew. Chem. Int. Ed. 2002, 41, 853. (c) Takeuchi, M.; Tanaka, S.; Shinkai, S. Chem. Commun. 2005, 5539. (d) Morikawa, M.-a.; Yoshihara, M.; Endo, T.; Kimizuka, N. J. Am. Chem. Soc. 2005, 127, 1358. (e) O’Dwyer, C.; Navas, D.; Lavayen, V.; Benavente, E.; Sanata Ana, M. A.; González, G.; Newcomb, S. B.; Sotomayor Torres, C. M. Chem. Mater. 2006, 18, 3016.  7.  For recent examples, see: (a) Rosselli, S.; Ramminger, A.-D.; Wagner, T., Silier, B.; Wiegand, S.; Häußler, W.; Lieser, G.; Scheumann, V.; Höger, S. Angew. Chem. Int. Ed. 2001, 40, 3137. (b) Höger, S.; Bonard, K.; Rosselli, S.; Ramminger, A.-D.; Macromol. Symp. 2002, 177, 185. (c) Venkataraman, D.; Lee, S.; Zhang, J.; Moore, J. S. Nature 1994, 371, 591. (d) Zhao, D.; Moore, J. S. Chem. Commun. 2003, 807.  8.  Kawano, S.; Tamaru, S.; Fujita, N.; Shinkai, S. Chem. Eur. J. 2004, 10, 343.  9.  Balakrishnan, K.; Datar, A.; Zhang, W.; Yang, X.; Naddo, T.; Huang, J.; Zuo, J.; Yen, M.; Moore, J. S.; Zang, L. J. Am. Chem. Soc. 2006, 128, 6576.  159  10. For examples of aggregation of zinc porphyrins, see: (a) Abraham, R. J.; Fell, S. C.; Pearson, H.; Smith, K. M. Tetrahedron 1979, 35, 1759. (b) Kishida, T.; Fujita, N.; Hirata, O.; Shinkai, S. Org. Biomol. Chem. 2006, 4, 1902. 11. Binder, W. H.; Smrzka, O. W. Angew. Chem. Int. Ed. 2006, 45, 7324. 12. For recent examples of gelation, see: (a) Sugiyasu, K.; Fujita, N.; Shinkai, S. J. Mater. Chem. 2005, 15, 2747. (b) Lebel, O.; Perron, M.-E.; Maris, T.; Zalzal, S. F.; Nanci, A.; Wuest, J. D. Chem. Mater. 2006, 18, 3616. (c) Kume, S.; Kuroiwa, K.; Kimizuka, N. Chem. Commun. 2006, 2442. (d) Weng, W.; Beck, J. B.; Jamieson, A. M.; Rowan, S. J. J. Am. Chem. Soc. 2006, 128, 11663. (e) Camerel, F.; Bonardi, L.; Schmutz, M.; Ziessel, R. J. Am. Chem. Soc. 2006, 128, 4548. (f) John, G.; Zhu, G.; Li, J.; Dordick, J. S. Angew. Chem. Int. Ed. 2006, 45, 4772. 13. (a) Reglinski, J.; Morris, S.; Stevenson, D. E. Polyhedron 2002, 21, 2175. (b) Odoko, M.; Tsuchida, N.; Okabe, N. Acta Crystallogr. Sect. E 2006, 62, m708. (c) Sanmartín Matalobos, J.; Garcia-Deibe, A. M.; Fondo, M.; Navarro, D.; Bermejo, M. R. Inorg. Chem. Commun. 2004, 7, 311. (d) Singer, A. L.; Atwood, D. A. Inorg. Chim. Acta 1998, 277, 157. 14. Kleij, A. W.; Kuil, M.; Lutz, M.; Tooke, D. M.; Spek, A. L.; Kamer, P. C. J.; van Leeuwen, P. W. N. M.; Reek, J. N. H. Inorg. Chim. Acta 2006, 359, 1807. 15. Ma, C. T. L.; MacLachlan, M. J. Angew. Chem. Int. Ed. 2005, 44, 4178. 16. Batley, G. E.; Graddon, D. P. Aust. J. Chem. 1967, 20, 885. 17. (a) Kishida, T.; Fujita, N.; Sada, K.; Shinkai, S. J. Am. Chem. Soc. 2005, 127, 7298. (b) Kishida, T.; Fujita, N.; Sada, K.; Shinkai, S. Langmuir 2005, 21, 9432. 18. (a) Kim, D.-H.; Choi, M. J.; Chang, S.-K. Bull. Korean Chem. Soc. 2000, 21, 145. (b) 160  Yilmaz, I.; Bekâroğlu, Ö. J. Chem. Res. 1998, (S) 374; (M) 1585. 19. Hui, J. K.-H.; Yu, Z., Mirfakhrai, T.; MacLachlan, M. J. Chem. Eur. J. 2009, 15, 13456. 20. Brooker, S.; Croucher, P. D.; Davidson, T. C.; Dunbar, G. S.; Beck, C. U.; Subramanian, S. Eur. J. Inorg. Chem. 2000, 169. 21. DeLano, W. L. The PyMOL Molecular Graphics System (2002) on World Wide Web (http://www.pymol.org).  161  CHAPTER 6 SELF-ASSEMBLY OF CARBOHYDRATEFUNCTIONALIZED ZINC(II) SALPHEN COMPLEXES INTO HELICAL NANOFIBERS †  6.1 Introduction  Supramolecular  self-assembly  of  molecules  and  macromolecules  into  one-dimensional long-range-ordered nanofibers through non-covalent interactions, such as hydrogen-bonding and intermolecular π-π stacking, 1 has received a lot of attention in the recent years. The molecule-based construction approach to fibrous nanostructures provides a way to diversify the properties of the aggregates by tuning the functionalities of the building blocks. Nanofibers are an exciting class of materials as these supramolecular aggregates have useful applications in nanosized electronic,2 mechanical 3 and medical fields. 4  The hydrogen-bonding ability of carbohydrates may be used to aggregate supramolecular complexes. 5 For instance, Shinkai and co-workers reported a library of low-molecular weight monosaccharide gelators that exhibit fibrous aggregates. 6 They also found that peripheral carbohydrates on porphyrins can help in the formation of stable †  A version of this chapter has been published as an article: Hui, J. K.-H.; Yu, Z.; Mirfakhrai, T.;  MacLachlan, M. J. “Supramolecular Assembly of Carbohydrate-Functionalized Salphen-Metal Complexes” Chem. Eur. J. 2009, 15, 13456.  162  xerogels, which can then be used as the templates for helical silica superstructures. 7 Macrocycles such as calix[4]resorcarenes and cucurbiturils may be functionalized with oligosaccharides to give macrocyclic glycoclusters and porous aggregates. 8 These new supramolecular structures with biocompatible carbohydrate surfaces are attractive for drug delivery agents.  Metal-salen and metal-salphen derivatives have been studied extensively for their use in catalysis, 9 for oxygen storage/release, 10 and for chemical sensing. 11 More recently, the supramolecular organization of metal-salphen complexes has proven a promising route to new materials. 12 It is surprising that few carbohydrate-functionalized salen derivatives have been reported thus far and none have been investigated for supramolecular assembly. Nevertheless, there has been a great deal of research devoted to the functionalization of coordination complexes with carbohydrates. These substances combine the advantages of the metal complexes, such as catalysis, with the favorable properties of the carbohydrates – water solubility, hydrogen-bonding, and specific recognition capabilities – to produce molecules with new function. The enantiomeric purity of natural carbohydrates renders them particularly useful for developing metal complexes for asymmetric catalysis. 13 For example, manganese(III) salen complexes with chiral carbohydrate groups demonstrate good enantioselectivity for asymmetric epoxidation of non-functionalized olefins. 14 Orvig and co-workers have investigated salen-based ligands with glucose attached as metal-chelating agents for treating Alzheimer’s disease. 15  163  Our research group has been interested in the supramolecular assembly of Schiff-base macrocycles based on salphen. 16,17 With the notion that hydrogen bonding between monosaccharides could facilitate supramolecular assembly of salphen complexes or macrocycles, a series of new Schiff-base complexes with appended glucosyl or galactosyl groups were prepared. In Chapter 5, carbohydrate-functionalized zinc(II) salphen complexes were found to form one-dimensional supramolecular structures that could be imaged by TEM. 18 The reason to incorporate peripheral glucose and galactose on the salphen complexes and study their supramolecular behaviors is because they can be used as model compounds for Schiff-base macrocycles with carbohydrate substituents. The macrocycles utilize the intermolecular hydrogen-bonding ability of carbohydrates in hope of self-assembling into one-dimensional structures with hollow channels that can potentially be used for host-guest chemistry. This chapter focuses on the studies of the synthesis, characterization, and the morphology of the supramolecular assembly of monosaccharide-functionalized salphen complexes 43f,g, 54c,d, and 58a–f (Figure 6.1).  Figure 6.1. Chemical structures of salphen complexes 43f,g, 54c,d, and 58a–f.  164  6.2 Results and Discussion  6.2.1 Synthesis and Characterization of Metallosalphen Complexes 43f,g, 54c,d, and 58a–f  With the long term goal of forming Schiff-base macrocycles that are externally functionalized  with  carbohydrate  groups,  o-phenylenediamine  substituted  with  carbohydrates in the 4,5 positions was required. These particular compounds were unknown and, in fact, there are no examples of two carbohydrates attached to ortho positions on the same phenyl ring; it was uncertain that the compounds could be formed as they look very sterically crowded. Scheme 6.1 shows our route to these compounds. Dinitrocatechol (59) was prepared by a literature procedure then was coupled with acetyl-protected carbohydrate derivatives 60 by the Koenigs-Knorr reaction. To our surprise, two carbohydrate moieties were able to attach ortho to one another on the dinitrocatechol 59 and obtained compound 61 in 60–70% yield. According to the literature preparation for glycoside synthesis in the presence of silver(I) oxide, having an equatorial acetyl protecting group at C2 position of the glycopyranosyl bromide 60 would induce the formation of a β-anomeric product. 19 To confirm that the carbohydrate moieties have β-anomeric centers, a single crystal XRD study of the acetyl-protected galactose-functionalized dinitrobenzene 61b was undertaken. 20 The solid-state structure of the compound (Figure 6.2) verified that the two galactosyl components have β-anomeric centers. The galactose moieties retain the chair conformation and the compound itself possesses C2 rotational symmetry. It packs in an orthorhombic lattice, 165  which contains four compound 61b molecules in each unit cell. The molecules overlap directly on top of each other along the a-axis, but are offset along the c-axis. As they extend along the b-axis, the molecule flips in an alternating fashion.  Scheme 6.1. Syntheses of dinitrobenzenes 61 and phenylenediamines 46g,h.  166  Figure 6.2. (a) Top view and (b) side view of the crystal structure of acetyl-protected galactose-functionalized dinitrobenzene 61b. The hydrogen atoms have been removed for clarity, except the anomeric hydrogen in the side view to show the β-conformation. The acetyl-protecting groups are also removed for clarity in the side view. (Color legend: carbon = black, hydrogen = white, nitrogen = blue, oxygen = red)  The dinitrobenzenes functionalized with acetyl-protected glucose 61a and galactose 61b were then reduced to yield o-phenylenediamines 46. Reduction with hydrazine using a  Pd/C  or  Raney  nickel  catalyst,  reagents  that  worked  well  to  reduce  1,2-dialkoxy-4,5-dinitrobenzenes, resulted in cleavage of some of the acetyl protecting groups as determined by NMR spectroscopy of the products. The resulting partially-deprotected species prevented isolation of pure compound 46. Fortunately, this problem was overcome by using ammonium formate as the reducing agent. With this 167  procedure,  the  air-sensitive  acetyl-protected  carbohydrate-functionalized  phenylenediamines 46g,h were obtained in 70–80% yield.  After the preparation of phenylenediamines 46g,h was completed, they were reacted with salicylaldehyde in situ with the presence of different metal(II) acetylacetonates under nitrogen to obtain metal salphen complexes 62 and 63 (Scheme 6.2). The acetyl protecting groups on the carbohydrate moieties were then cleaved by the use of base (i.e., sodium methoxide or triethylamine) in methanol to yield the target complexes 43f,g, 54c,d, and 58a–f (Scheme 6.2).  168  RO RO  OR O  + H2N  2.2  1.5 M(acac)2  OH  N  THF  NH2  46g R = AcO AcO  O  O AcO  AcOOAc O AcO  N M  OAc  46h R =  OR  AcO  RO  OR  O  62a 62b 62c 62d 62e  M = Zn OAc M = Ni O M = VO R = AcO M = Fe AcO AcO M = Cu  63a 63b 63c 63d 63e  M = Zn AcOOAc M = Ni O M = VO R = M = Fe AcO AcO M = Cu  Et3N, MeOH or NaOMe, MeOH  N  N M  O  O  43f 54c 58a 58c 58e  M = Zn OH M = Ni M = VO R = HO M = Fe HO M = Cu  43g 54d 58b 58d 58f  M = Zn HOOH M = Ni M = VO R = M = Fe HO M = Cu  O HO  O HO  Scheme 6.2. Syntheses of acetyl-protected metal salphen complexes 62 and 63, and metal salphen complexes 43f,g, 54c,d, and 58a–f.  The MALDI-TOF or ESI mass spectra of the complexes indicated the successful deacetylation for most of the complexes, but the deprotection of the acetyl groups did not 169  go to completion for some of the metal complexes 62 and 63 (i.e., complexes 62c, 63c–e). There was always mono- or di-acetyl-protected complexes still present in the sample and they could not be easily removed by purification. Therefore, another route was developed to reach the target glucosyl- and galactosyl-metallosalphen complexes (Scheme 6.3). Compound 61 was first deacetylated with triethylamine in methanol to yield compound 64, followed by reduction by hydrazine with Pd/C catalyst to obtain the new glycopyranosyl phenylenediamines 46i,j. Metal salphen complexes 58a,b,d,f were then synthesized by reacting compound 46i or 46j with salicylaldehyde and the corresponding metal salts. This method successfully overcame the problem of incomplete deprotection, and MALDI-TOF or ESI mass spectra of the resultant complexes showed only the expected products.  Scheme 6.3. Syntheses of the new phenylenediamines 46i,j.  170  6.2.2 Morphological study of the Supramolecular Self-assemblies of the Metal Salphen Complexes  Since carbohydrates are known to facilitate supramolecular assembly, the solid-state structures obtained from the glucose- and galactose-appended metal complexes were examined by electron microscopy. A series of TEM studies was performed by drop-casting methanol solutions of the metallated carbohydrate species onto Formvar carbon-coated grids and viewing them under the electron microscope. Supramolecular structures were observed and their morphologies are strongly dependent on the metal center being coordinated in the pocket of the salphen complexes.  Representative TEM micrographs of the metal complexes 43f,g, 54c,d, and 58a–f are shown in Figure 6.3. The complexes of vanadyl, iron(II), nickel(II) and copper(II) all show similar cluster assemblies (Figures 6.3a–d,f–i). The petal-like aggregates in each case are microns in size and most likely are dominated by hydrogen-bonding interactions between the carbohydrate substituents. There is no apparent difference between the two sets of metal complexes with glucosyl and galactosyl substituents (54c,d, and 58a–f). Vanadyl salphen complexes are known to form polymeric structures with the neighboring units through the ···V-O-V-O··· linking pattern, 21 which would be expected to affect the supramolecular assembly. However, the observation of an absorption band at 980 cm-1 in the IR spectra for complexes 58a,b confirms that the V=O complexes are not coordinated into an extended network (the V-O stretch is observed at 860 cm-1 in the case of polymers).21 171  Figure 6.3. TEM images of (a–e) glucose-functionalized metal salphen complexes 58a, 58c, 54c, 58e and 43f and (f–j) galactose-functionalized metal salphen complexes 58b, 58d, 54d, 58f and 43g, respectively. 172  In contrast to the other metal complexes, the zinc(II) complexes display a fibrillar morphology (Figures 6.3e,j). The discrete nanofibers were found to be microns in length and tens of nanometers in diameter. Clearly, there is a different interaction promoting the self-assembly in this case. Zinc(II) salphen complexes are well-known to behave as Lewis acids, and either coordinate Lewis bases (e.g., pyridine) to the unsaturated metal centers,12,17,22 or aggregate whereby the zinc of one salphen complex is coordinated to the phenoxy oxygen of another. 23 Dimerization of the zinc(II) salphen complexes through this Zn···O interaction may be responsible for changing the molecular shape of the molecule sufficiently that it organizes into a fibrillar structure. Alternatively, the Zn···O interaction may extend beyond a dimer and yield a polymeric structure with a (ZnO)n backbone.18 This Zn···O interaction appears to dominate over the hydrogen-bonding interactions of the peripheral glycopyranosyl groups in directing the structure.  The supramolecular structures of salphen complexes 43f, 54c, and 58a,c,e were also studied with AFM. Methanol solutions of complexes 43f, 54c, and 58a,c,e were drop-cast onto individual microscope glass slides and imaged with AFM by scanning with tapping mode (Figure 6.4). The AFM micrographs generally correlate with the morphologies that were observed from TEM. The vanadyl, iron(II), nickel(II) and copper (II) complexes display micron-sized clusters with no defining features. On the other hand, zinc(II) salphen complex 43f displays well-defined fibers (Figure 6.4e). The fibers are mostly straight, and have diameters of 78±13 nm (based on a count of 100) and extend for microns. The size of the fibers is larger than observed from TEM, and this may be  173  Figure 6.4. AFM images of (a–e) glucose-functionalized metal salphen complexes 58a, 58c, 54c, 58e and 43f, respectively. Insets of (e) top: a closer look of the rectangular-boxed region; bottom, a histogram of the widths of 100 nanofibers counted in (e). 174  explained by two factors: the tip convolution arising from the AFM and sample variation (the fiber density is greater in the case of the AFM sample).  Closer observation of the fibers reveals that they all have helical superstructures (Figure 6.4e inset) and all of the helices are left-handed. The helical pitches measured by AFM range from about 30 to 80 nm. A representation of the helical segment is as shown in Figure 6.5.  Figure 6.5. Graphic representation of the helicity in the fibers of zinc(II) salphen complex 43f.  The helical superstructure of the zinc(II) salphen molecules is surprising and not easily explained as the fiber must contain hundreds of the salphen molecules in diameter. We have modeled the Zn···O polymer that may form from the zinc(II) salphen assembly, and this polymer could have a helical structure.18 This helical polymer structure may be projected onto the superstructure morphology that was observed. As the sugar complexes  175  are the only source of chirality in the complex, they must be responsible for directing the helicity since all of the helices have the same direction.  Helical fibers have been observed with other carbohydrate-based molecules or receptors 24 and other synthetic assemblies. 25 Moreover, fibrous aggregates with a helical morphology can be found in biological systems. For instance, amino acids and sugars can act as supramolecular building units and direct the assembly of helical nanofibers, such as collagen, amyloid and keratin. 26  Shinkai and co-workers have reported that carbohydrate substituents could also be used to promote gelation. 27 Therefore, investigations on such phenomena for our metal salphen complexes that are functionalized with glucose and galactose were performed. Among all complexes (43f,g, 54c,d, and 58a–f) and their acetyl derivatives (62–63) that were synthesized, gelation only occurred for nickel(II) salphen complex 62b and copper(II) salphen complex 63e appended with acetyl-protected glucose and galactose substituents, respectively. In these cases, the gels formed when the corresponding methanol solution was slowly evaporated. Figure 6.6 shows TEM images of the gels of complexes 62b and 63e. From the micrographs, helical bundles were noticed for nickel(II) salphen complex 62c (Figure 6.6a). When the nickel gel was diluted in methanol and inspected further with TEM, the morphology, however, changed from helical bundles to spheres that are linked together (Figure 6.6b). It is believed that the intermolecular interaction between the nickel(II) salphen complex was weakened in the diluted sample, leading to a change in morphology. Copper(II) salphen complex 63e showed a nanofibrillar morphology when viewed under TEM (Figure 6.6c). The one-dimensional 176  fibers are similar to those observed for zinc(II) complexes 43f,g, but the fibers of complex 63e are much shorter, extending only a few hundreds of nanometers. Here, the acetyl groups prevent strong interactions between the carbohydrate groups, and the assembly is likely maintained by stacking of the copper(II) salphen complex groups, known to be nearly flat. No obvious change in the fibril texture was observed as the gel was diluted in methanol.  Figure 6.6. TEM images of the gels of (a) acetyl-protected glucose-functionalized nickel(II) salphen complex 62b and (b) diluted in methanol; (c) acetyl-protected galactose-functionalized copper(II) salphen complex 63e and (d) diluted in methanol.  177  6.3 Conclusions  A series of metal salphen complexes functionalized with peripheral carbohydrates and their acetate-protected derivates has been prepared through two different routes. The use of carbohydrates facilitates the solid-state clustering of the metal complexes as determined by TEM and AFM studies. Surprisingly, the zinc complexes showed a one-dimensional fibrillar assembly that extends over microns in length while the other metal complexes (vanadyl, iron(II), nicke(II), copper(II)) showed a cluster morphology that looks like aggregation of sheets packed into ball-shaped agglomerates. AFM clearly showed that the zinc complexes organize into helical assemblies where the helicity of the fibers is left handed. It is clear that while the carbohydrates have a role in the supramolecular organization of the complexes, the metal has a surprisingly significant and differential role in directing the structure. Further study of the aggregation and textures of the zinc(II)-containing complexes may give useful insight into biological structures, including zinc-rich plaques implicated in Alzheimer’s disease.  6.4 Experimental  General procedures: All reactions were carried out under nitrogen atmosphere by means of standard Schlenk techniques unless otherwise stated. Tetrahydrofuran was distilled from sodium/benzophenone under nitrogen. Acetonitrile, methanol, and triethylamine were purged with nitrogen gas and dried over molecular sieves before use. Deuterated solvents were obtained from Cambridge Isotope Laboratories, Inc.. All reagents were 178  used as received unless otherwise stated. Ammonium formate, hydrazine, salicylaldehyde, vanadyl acetylacetonate, iron(II) acetylacetonate, nickel(II) acetylacetonate, copper(II) acetylacetonate, zinc(II) acetylacetonate, triethylamine and sodium methoxide were obtained from Aldrich. Silver(I) oxide was obtained from Strem. Palladium on carbon was obtained from Pressure Chemical. Nitric acid was obtained from Fisher. 4,5-Dinitrocatechol (59), 28 tetra-O-acetyl-α-D-glucopyranosyl bromide (60a), 29 and tetra-O-acetyl-α-D-galactopyranosyl bromide (60b)29 were prepared by literature methods.  Equipment. 300 MHz 1H and 75.5 MHz  13  C NMR spectra were recorded on a Bruker  AV-300 spectrometer. 400 MHz 1H and 100.6 MHz 13C NMR spectra were recorded on a Bruker AV-400 spectrometer. UV-vis spectra were collected in methylene chloride, dimethyl sulfoxide and methanol on a Varian Cary 5000 UV-vis/near-IR spectrometer using a 1 cm cuvette. Mass spectra and elemental analyses were obtained at the UBC Microanalytical Services Laboratory. MALDI mass spectra were obtained on a Bruker Biflex IV TOF mass spectrometer equipped with a MALDI ion source. ESI mass spectra were obtained on a Bruker Esquire-LC ion trap mass spectrometer equipped with an electrospray ion source. HR-ESI mass spectra were obtained on a Micromass LCT TOF mass spectrometer equipped with an electrospray ion source. Samples for both ESI and HR-ESI were analyzed in methanol, methanol/DMSO mixture or methanol/methylene chloride mixture at 1 μM. Gramicidin S, Rifampicin, and Erythromycin were used as the references for HR-ESI mass spectrometry. EI mass spectra were recorded on a Kratos MS-50 double focusing sector mass spectrometer equipped with an EI ion source. Elemental analyses were obtained on a Carlo Erba Elemental Analyzer EA 1108. Melting 179  points were obtained on a Fisher-John’s melting point apparatus. TEM images were obtained at the UBC BioImaging Facility on a Hitachi H7600 transmission electron microscope. Samples were prepared by dissolving the compounds in methanol and drop-casting onto carbon-coated grids. AFM was performed on an Asylum Research MFP-3D-SA atomic force microscope. Samples were prepared by dissolving the compounds in methanol mixture and drop-casted onto microscope glass slides. An Olympus AC 240TM silicon cantilever was used in tapping (ac) mode. IR spectra were obtained using a Thermo Scientific Nicolet 6700 FT-IR spectrometer equipped with a diamond Attenuated Total Reflectance.  More Information on Crystallography. Crystals of compound 61b suitable for X-ray diffraction were grown from methanol by slow evaporation. All measurements were made on a Bruker X8 diffractometer with graphite monochromated Mo-Kα radiation (λ = 0.71073 Å). The data were collected at a temperature of -100.0 ± 0.1°C to a maximum 2θ value of 54.28°. Data were collected in a series of φ and ω scans in 0.50° oscillations with 15 sec exposures. Of the 21309 reflections that were collected, 8839 were unique (Rint = 0.0377); equivalent reflections were merged. Data were collected and integrated using the Bruker SAINT software package. 30 Data were corrected for absorption effects using a multi-scan technique (SADABS), 31 with max and min transmission coefficients of 0.970 and 0.756, respectively. The data were corrected for Lorentz and polarization effects. The structure was solved by direct methods. 32 All non-hydrogen atoms were refined anisotropically. All hydrogen atoms were included in calculated positions but not refined. The Flack parameter was determined to be -0.2 with an esd of 0.9; this does not give the absolute stereochemistry, but the stereochemistry of the structure was easily verified by 180  the configurations of the chiral centers in the glucose substituents. The final cycle of full-matrix least-squares refinement on F2 was based on 8839 reflections and 541 variable parameters and converged (largest parameter shift was 0.032 times its esd). 33 CCDC-740867 contains the supplementary crystallographic. These data can be obtained free  of  charge  from  the  Cambridge  Crystallographic  Data  Centre  via  www.ccdc.cam.ac.uk/data_request/cif.  Synthesis of 1,2-Bis(tetra-O-acetyl-β-D-glucopyranosyl)-4,5-dinitrobenzene (61a). Tetra-O-acetyl-α-D-glucopyranosyl bromide (60a) (8.42 g, 20.5 mmol) was dissolved in acetonitrile (150 mL) to give a colorless solution. The solution was purged with nitrogen for 15 min, then 4,5-dinitrocatechol (59) (1.65 g, 8.25 mmol) and silver(I) oxide (4.63 g, 20.5 mmol) were added sequentially under nitrogen. The resulting mixture, which was very dark in color, was stirred at 50 oC for 24 h. After cooling to room temperature, the mixture was filtered through a thin layer of celite to obtain a brownish solution. The solvent was removed by rotary evaporation to give a dark brown solid. Chromatography on silica gel (1:1 hexanes/ethyl acetate), followed by recrystallization in methanol yielded compound 61a (4.12 g, 58%, colorless plates).  Data for 1,2-Bis(tetra-O-acetyl-β-D-glucopyranosyl)-4,5-dinitrobenzene (61a).  1  H  NMR (300 MHz, chloroform-d1) δ 7.65 (s, 2H, aromatic CH), 5.29 (m, 2H, CH), 5.21 (m, 4H, CH), 5.10 (t, 2H, CH), 4.17 (m, 4H, CH), 3.96 (m, 2H, CH), 2.08 (s, 6H, CH3), 2.07 (s, 6H, CH3), 2.05 (s, 6H, CH3), 2.01 (s, 6H, CH3) ppm.  13  C NMR (75.5 MHz,  chloroform-d1) δ 170.5, 170.0, 169.4, 168.8 (C(O)CH3), 149.1, 138.1, 113.4 (aromatic C) 99.0, 73.0, 72.3, 70.7, 67.9, 62.0 (CH), 20.5, 20.4 (CH3) ppm. ESI-MS: m/z = 883.3 181  ((M+Na)+). IR: υ = 1754 (m), 1742 (m), 1697 (w), 1600 (w), 1548 (m), 1539 (m), 1511 (m), 1430 (w), 1418 (w), 1375 (m), 1367 (m), 1340 (w), 1294 (m), 1247 (m), 1219 (s), 1212 (s), 1125 (m), 1079 (s), 1034 (s), 968 (m), 922 (m), 895 (m), 870 (m), 816 (m), 761 (w), 754 (w), 725 (w), 701 (w), 682 (w), 665 (w), 644 (w), 601 (m) cm-1. UV-vis (methylene chloride): λmax (ε) = 262 (7.92x103), 278 (7.77x103) nm (cm-1 mol-1 L). Anal. Calc’d (%) for 61a (C34H40N2O24): C 47.45, H 4.68, N 3.25; Found: C 47.67, H 4.75, N 3.49. m.p. = 214–215 oC.  Synthesis of 1,2-Bis(tetra-O-acetyl-β-D-galactopyranosyl)-4,5-dinitrobenzene (61b). Compound 61b was prepared by the same procedure as for compound 61a. Chromatography on silica gel (1:2 hexanes/ethyl acetate), followed by recrystallization in methanol yielded compound 61b (66%, colorless needles).  Data for 1,2-Bis(tetra-O-acetyl-β-D-galactopyranosyl)-4,5-dinitrobenzene (61b).  1  H  NMR (400 MHz, chloroform-d1) δ 7.68 (s, 2H, aromatic CH), 5.45 (m, 4H, CH), 5.19 (d, 2H, CH), 5.13 (d, 2H, CH), 4.16 (m, 6H, CH), 2.17 (s, 6H, CH3), 2.09 (s, 6H, CH3), 2.07 (s, 6H, CH3), 2.00 (s, 6H, CH3) ppm.  13  C NMR (100.6 MHz, chloroform-d1) δ 171.5,  170.9, 169.7 (C(O)CH3), 150.2, 139.1, 114.7 (aromatic C) 100.6, 73.3, 71.5, 69.1, 68.0, 62.9 (CH), 21.6, 21.5, 21.4 (CH3) ppm. ESI-MS: m/z = 883.3 ((M+Na)+). IR: υ = 1739 (s), 1597 (w), 1538 (m), 1511 (m), 1431 (w), 1414 (w), 1367 (m), 1360 (m), 1285 (m), 1273 (m), 1248 (m), 1216 (s), 1145 (w), 1125 (m), 1065 (s), 1037 (s), 969 (m), 943 (w), 914 (m), 892 (m), 881 (m), 839 (w), 831 (w), 813 (m), 768 (w), 756 (w), 744 (w), 721 (w), 713 (w), 669 (w), 656 (w), 628 (w), 590 (m) cm-1. UV-vis (methylene chloride): λmax (ε) = 314 (3.72x103) nm (cm-1 mol-1 L). Anal. Calc’d (%) for 61b (C34H40N2O24): C 47.45%, 182  H 4.68, N 3.25; Found: C 47.44, H 4.76, N 3.43. m.p. = 198–199 oC.  Synthesis of 4,5-Bis(tetra-O-acetyl-β-D-glucopyranosyl)phenylenediamine (46g). Compound 61a (2.30 g, 2.67 mmol) was dissolved in methanol (65 mL) and the solution was purged with nitrogen for 15 min. Palladium on carbon (2 spatula tips) and ammonium formate (1.35 g, 21.4 mmol) were then added to the flask under nitrogen. The resulting mixture was stirred at 70 oC for 2 h until the solution became clear colorless. After cooling to room temperature, the catalyst was removed by filtration through a Schlenk frit and a colorless filtrate was obtained. The solvent was then removed under vacuum. Degassed water and chloroform were added to the flask and the product was extracted into the chloroform under nitrogen. Chloroform removal under vacuum yielded air-sensitive compound 46g (1.39 g, 65%, purple solid). This compound was > 99% pure (1H NMR) and was used without further purification. Attempts to remove colored impurities resulted in further decomposition, so it was best to purify at the next stage.  Data for 4,5-Bis(tetra-O-acetyl-β-D-glucopyranosyl)phenylenediamine (46g).  1  H  NMR (400 MHz, chloroform-d1) δ 6.45 (s, 2H, aromatic CH), 5.22 (t, 2H, CH), 5.11 (q, 4H, CH), 5.03 (d, 2H, CH), 4.27 (d, 2H, CH), 4.09 (d, 2H, CH), 3.67 (d, 2H, CH), 3.47 (broad, 4H, NH2) 2.07 (s, 6H, CH3), 2.04 (s, 6H, CH3), 2.00 (s, 6H, CH3), 1.99 (s, 6H, CH3) ppm.  13  C NMR (100.6 MHz, chloroform-d1) δ 170.5, 170.1, 169.3, 169.2  (C(O)CH3), 140.2, 131.1, 109.6 (aromatic C) 100.7, 72.8, 71.9, 71.4, 68.2, 61.6 (CH), 20.6, 20.5, 20.5, 20.4 (CH3) ppm. EI-MS: m/z = 800 ((M+H)+).  183  Synthesis of 4,5-Bis(tetra-O-acetyl-β-D-galactopyranosyl)phenylenediamine (46h). Compound 46h (83%, greenish solid) was prepared by the same procedure and purification as for compound 46g. This compound was ~90% pure (1H NMR) and was used without further purification. Attempts to obtain a pure product resulted in further decomposition, so it was best to purify at the next stage.  Data for 4,5-Bis(tetra-O-acetyl-β-D-galactopyranosyl)phenylenediamine (46h).  1  H  NMR (400 MHz, chloroform-d1) δ 6.47 (s, 2H, aromatic CH), 5.35 (m, 4H, CH), 5.06 (d, 2H, CH), 4.99 (d, 2H, CH), 4.21 (q, 2H, CH), 4.12 (q, 2H, CH), 3.90 (t, 2H, CH), 3.29 (broad, 4H, NH2) 2.17 (s, 6H, CH3), 2.10 (s, 6H, CH3), 1.99 (s, 6H, CH3), 1.97 (s, 6H, CH3) ppm.  13  C NMR (100.6 MHz, chloroform-d1) δ 170.5, 170.4, 170.3, 169.6  (C(O)CH3), 140.9, 131.4, 109.8 (aromatic C) 101.7, 71.2, 71.1, 69.2, 67.4, 61.5 (CH), 21.0, 20.8, 20.7 (CH3) ppm. EI-MS: m/z = 800 ((M+H)+.  Synthesis of 1,2-Bis(β-D-glucopyranosyl)-4,5-dinitrobenzene (64a). Triethylamine (20 mL) was added to a Schlenk flask containing compound 61a (0.500 g, 0.581 mmol) and dry methanol (30 mL). The yellow solution was stirred at room temperature for 2 d. The solvent was then removed by rotary evaporation at 50 oC to obtain a yellow solid. Recrystallization of the crude product with methanol/ethanol mixture yields compound 64a (0.253 g, 83%, off-while solid).  Data for 1,2-Bis(β-D-glucopyranosyl)-4,5-dinitrobenzene (64a). 1H NMR (300 MHz, DMSO-d6) δ 7.91 (s, 2H, aromatic CH), 5.39 (d, 2H, CH), 5.22 (d, 2H, CH), 5.16 (d, 2H, CH), 5.08 (d, 2H, CH), 4.60 (t, 2H, CH), 3.66 (m, 4H, CH), 3.49 (m, 4H, OH), 3.18 184  (broad, 2H, OH) ppm. 13C NMR (100.6 MHz, DMSO-d6) δ 149.4, 136.5, 112.2 (aromatic C) 100.13, 77.3, 76.5, 73.0, 69.4, 60.5 (CH) ppm. ESI-MS: m/z = 547.3 ((M+Na)+), 1071.5 ((2M+Na)+). IR: υ = 3592 (m), 3363 (w), 1594 (w), 1547 (m), 1524 (s), 1511 (m), 1464 (w), 1387 (w), 1367(m), 1345 (m), 1284 (m), 1267 (m), 1219 (m), 1138 (m), 1076 (s), 1036 (s), 1020 (m), 986 (m), 925 (m), 903 (w), 889 (m), 867 (w), 815 (m), 785 (m), 753 (m), 701 (w), 669 (m), 648 (m), 617 (m) cm-1. UV-vis (DMSO): λmax (ε) = 270 (7.59x103), 306 (6.24x103) nm (cm-1 mol-1 L). Anal. Calc’d (%) for 64a (C18H24N2O16): C 41.35, H 4.54, N 5.19; Found: C 41.23, H 4.61, N 5.34. m.p. = 168–170 oC (turned black as it melted).  Synthesis of 1,2-Bis(β-D-galactopyranosyl)-4,5-dinitrobenzene (64b). Triethylamine (100 mL) was added to a Schlenk flask containing compound 61b (4.00 g, 4.65 mmol) and dry methanol (140 mL). The yellow solution was stirred at room temperature for 3 d, resulting in a pale yellow solid and yellow solution. Filtration of the solid yields compound 64b (2.06 g, 84%, pale-yellow solid) and no further purification was necessary.  Data for 1,2-Bis(β-D-galactopyranosyl)-4,5-dinitrobenzene (64b). 1H NMR (400 MHz, DMSO-d6) δ 7.91 (s, 2H, aromatic CH), 5.28 (d, 2H, CH), 5.19 (d, 2H, CH), 4.94 (d, 2H, CH), 4.67 (t, 2H, CH), 4.63 (d, 2H, CH), 3.69 (m, 6H, CH + OH), 3.51 (m, 4H, OH), 3.43 (m, 2H, OH) ppm. 13C NMR (100.6 MHz, DMSO-d6) δ 149.5, 136.3, 111.9 (aromatic C) 100.7, 75.8, 73.2, 69.9, 67.9, 60.2 (CH) ppm. ESI-MS: m/z = 547.2 ((M+Na)+), 1071.3 ((2M+Na)+). IR: υ = 3512 (m), 3355 (w), 1594 (w), 1548 (m), 1524 (s), 1512 (m), 1464 (w), 1388 (w), 1368 (m), 1344 (m), 1284 (m), 1267 (m), 1220 (m), 1139 (m), 1076 (s), 185  1035 (s), 1020 (m), 986 (m), 925 (m), 903 (w), 889 (m), 867 (w), 815 (m), 785 (m), 753 (m), 701 (w), 683 (w), 671 (w), 648 (m), 615 (m) cm-1. UV-vis (DMSO): λmax (ε) = 270 (8.05x103), 306 (7.00x103) nm (cm-1 mol-1 L). Anal. Calc’d (%) for 64b (C18H24N2O16): C 41.44, H 4.65, N 5.28; Found: C 41.23, H 4.61, N 5.34. m.p. = 185–187 oC (turned black as it melted).  Synthesis of 4,5-Bis(β-D-glucopyranosyl)phenylenediamine (46i). Compound 64a (0.200 g, 0.381 mmol) was added in ethanol (20 mL) and the mixture was purged with nitrogen for 15 min. Palladium on carbon (2 spatula tips) and hydrazine (1.50 mL, 30.9 mmol) were then added to the flask under nitrogen. The resulting mixture was stirred at 90 oC for 20 h until the solution became clear and colorless. Raney nickel (2 spatula tips) was added to the reaction flask under nitrogen and the mixture was refluxed for an additional 1.5 h in order to use up all the remaining hydrazine. After cooling down to room temperature, the catalyst was removed by filtration through a Schlenk frit and a colorless filtrate was obtained. The solvent was then removed under vacuum, yielding air-sensitive compound 46i (0.098 g, 55%, off-white solid). This compound was used without further purification. Attempts to remove colored impurities resulted in further decomposition, so it was best to purify at the next stage.  Data for 4,5-Bis(β-D-glucopyranosyl)phenylenediamine (46i). 1H NMR (400 MHz, DMSO-d6) δ 6.44 (s, 2H, aromatic CH), 5.16 (s, 2H, CH), 5.13 (s, 2H, CH), 5.05, (s, 2H, CH), 4.49 (d, 2H, CH), 4.35 (t, 2H, CH), 4.22 (s, 4H, NH2), 3.67 (d, 4H, CH), 3.48 (broad, 2H, OH), 3.15 (broad, 6H, OH) ppm. 13C NMR (100.6 MHz, DMSO-d6) δ 139.4, 130.8, 107.5 (aromatic C) 104.0, 77.0, 76.2, 73.7, 69.7, 60.8 (CH) ppm. 186  Synthesis of 4,5-Bis(β-D-galactopyranosyl)phenylenediamine (46j). Compound 46j was prepared by the same procedure and purification as for compound 46i.  Data for 4,5-Bis(β-D-galactopyranosyl)phenylenediamine (46j). 1H NMR (400 MHz, DMSO-d6) δ 6.42 (s, 2H, aromatic CH), 4.96 (s, 2H, CH), 4.77 (s, 2H, CH), 4.53, (s, 2H, CH), 4.44 (d, 2H, CH), 4.34 (s, 2H, CH), 4.35 (s, 2H, CH), 4.24 (broad, 4H, NH2), 3.67 (s, 4H, CH), 3.56 (broad, 2H, OH), 3.49 (broad, 6H, OH) ppm.  13  C NMR (100.6 MHz,  DMSO-d6) δ 139.5, 130.8, 107.6 (aromatic C) 104.6, 75.3, 73.0, 71.0, 67.8, 60.1 (CH) ppm.  Synthesis of Acetyl-protected Glucose-functionalized Zinc(II) Salphen Complex (62a). 4,5-Bis(tetra-O-acetyl-β-D-glucopyranosyl)phenylenediamine (46g) (0.300 g, 0.375 mmol) was dissolved in tetrahydrofuran (40 mL) under nitrogen. Salicylaldehyde (0.086 mL, 0.824 mmol) and zinc(II) acetylacetonate (0.148 g, 0.562 mmol) were then added, giving a yellow solution. The solution was stirred at 50 oC for 24 h. After cooling to room temperature, petroleum ether was added to the flask to precipitate the crude product solid, which was isolated by filtration. It was then purified by chromatography on silica gel (ethyl acetate) and yielded complex 62a (0.13 g, 32%, yellow solid).  Data for Acetyl-protected Glucose-functionalized Zinc(II) Salphen Complex (62a). 1  H NMR (400 MHz, DMSO-d6) δ 8.87 (s, 2H, CH=N), 7.59 (s, 2H, aromatic CH), 7.38 (d,  2H, aromatic CH), 7.24 (t, 2H, aromatic CH), 6.71 (d, 2H, aromatic CH), 6.53 (t, 2H, aromatic CH), 5.75 (d, 2H, CH), 5.34 (t, 2H, CH), 5.05 (q, 4H, CH), 4.26 (m, 4H, CH), 4.12 (d, 2H, CH), 2.04 (s, 6H, CH3), 2.03 (s, 6H, CH3), 1.99 (s, 6H, CH3), 1.91 (s, 6H, 187  CH3) ppm.  13  C NMR (100.6 MHz, DMSO-d6) δ 172.0 (CH=N), 170.0, 169.7, 169.3,  168.9 (C(O)CH3), 162.0, 145.4, 136.0, 135.0, 134.3, 123.2, 119.3, 113.0, 105.5 (aromatic C), 97.6, 72.2, 71.2, 70.7, 67.8, 61.5 (CH), 20.4, 20.3 (CH3) ppm. MALDI-TOF-MS: m/z = 1071.2 ((M+H)+), 1093.2 ((M+Na)+). HR-ESI-MS for 62a+Na+ (C48H50N2NaO22Zn): 1093.2044 (calculated), 1093.2057 (found). IR: υ = 1748 (s), 1614 (m), 1536 (m), 1503 (m), 1467 (m), 1442 (m), 1370 (m), 1295 (m), 1219 (s), 1175 (m), 1154 (m), 1118 (m), 1065 (s), 1036 (s), 984 (w), 935 (w), 914 (m), 810 (w), 761 (m), 741 (w), 599 (m) cm-1. UV-vis (methylene chloride): λmax (ε) = 298 (2.27x104), 339 (1.93x104), 377 (1.87x104) nm (cm-1 mol-1 L). m.p. = 187–190 oC (decomposition started at 180 oC).  Synthesis of Acetyl-protected Galactose-functionalized Zinc(II) Salphen Complex (63a). Complex 63a was prepared by the same procedure as for complex 62a. The product was purified by chromatography on silica gel (95:5 ethyl acetate/acetone) to yield complex 63a (42%, yellow solid).  Data for Acetyl-protected Galactose-functionalized Zinc(II) Salphen Complex (63a). 1  H NMR (300 MHz, DMSO-d6) δ 8.87 (s, 2H, CH=N), 7.60 (s, 2H, aromatic CH), 7.38 (d,  2H, aromatic CH), 7.25 (t, 2H, aromatic CH), 6.71 (d, 2H, aromatic CH), 6.54 (t, 2H, aromatic CH), 5.68 (d, 2H, CH), 5.40 (s, 2H, CH), 5.24 (m, 4H, CH), 4.45 (t, 2H, CH), 4.13 (d, 4H, CH), 2.16 (s, 6H, CH3), 2.09 (s, 6H, CH3), 1.97 (s, 6H, CH3), 1.84 (s, 6H, CH3) ppm.  13  C NMR (100.6 MHz DMSO-d6) δ 172.1 (CH=N), 170.0, 169.9, 169.6,  168.9 (C(O)CH3), 161.8, 145.7, 135.9, 134.9, 134.3, 123.2, 119.3, 113.0, 105.4 (aromatic C), 98.2, 70.8, 70.5, 68.4, 67.4, 61.5 (CH), 20.4 (CH3) ppm. MALDI-TOF-MS: m/z = 1071.2 ((M+H)+), 1093.4 ((M+Na)+), 2162.4 ((2M+Na)+). HR-ESI-MS for 63a+H+ 188  (C48H51N2O22Zn): 1071.2225 (calculated), 1071.2209 (found). IR: υ = 1748 (s), 1615 (m), 1537 (m), 1504 (m), 1467 (m), 1445 (m), 1370 (m), 1295 (m), 1219 (s), 1176 (m), 1153 (m), 1125 (m), 1069 (s), 1041 (s), 954 (w), 936 (w), 914 (m), 899 (m), 854 (w), 810 (w), 761 (m), 741 (m), 714 (w), 652 (w), 629 (w), 601 (m) cm-1. UV-vis (methylene chloride): λmax (ε) = 300 (2.29x104), 341 (1.99x104), 379 (1.95x104) nm (cm-1 mol-1 L). m.p. = 194–197 oC (decomposition started at 191 oC).  Synthesis of Glucose-functionalized Zinc(II) Salphen Complex (43f). Triethylamine (30 mL) was added to a solution of complex 62a (0.100 g, 0.09 mmol) in methanol (50 mL). The yellow solution was stirred at room temperature for 24 h. Methanol and excess triethylamine were then removed by rotary evaporation to give a yellow solid. The crude product was dissolved in methanol and re-precipitated with petroleum ether, followed by filtration to yield complex 43f (0.065 g, 94%, yellow solid).  Data for Glucose-functionalized Zinc(II) Salphen Complex (43f). 1H NMR (300 MHz, DMSO-d6) δ 8.87 (s, 2H, CH=N), 7.71 (s, 2H, aromatic CH), 7.36 (d, 2H, aromatic CH), 7.23 (t, 2H, aromatic CH), 6.70 (d, 2H, aromatic CH), 6.50 (t, 2H, aromatic CH), 5.28 (s, 2H, CH), 5.17 (s, 2H, CH), 5.12 (d, 2H, CH), 4.97 (d, 2H, CH), 4.88 (t, 2H, CH), 3.77 (m, 2H, CH), 3.48 (broad, 8H, OH), 3.21 (m, 2H, CH) ppm.  13  C NMR (100.6 MHz,  DMSO-d6) δ 171.9 (CH=N), 161.4, 146.9, 136.1, 134.1, 134.0, 123.0, 119.6, 112.9, 105.2 (aromatic C), 101.6, 77.5, 76.6, 73.4, 70.3, 61.1 (CH) ppm. ESI-MS: m/z = 735.2 ((M+H)+), 757.2 ((M+Na)+), 1471.6 ((2M+H)+), 1495.5 ((2M+Na)+). HR-ESI-MS for 43f+Na+ (C32H34N2NaO14Zn): 757.1199 (calculated), 757.1217 (found). IR: υ = 3351 (m), 2873 (w), 1614 (s), 1532 (m), 1500 (m), 1465 (m), 1440 (m), 1436 (m), 1386 (m), 1346 189  (w), 1293 (m), 1280 (m), 1246 (w), 1172 (m), 1153 (m), 1095 (m), 1065 (s), 1040 (s), 1014 (s), 934 (w), 915 (w), 875 (m), 811 (w), 755 (m), 669 (m), 603 (m) cm-1. UV-vis (methanol): λmax (ε) = 242 (2.75x104), 297 (2.49x104), 342 (1.66x104), 394 (2.68x104) nm (cm-1 mol-1 L). UV-vis (solid): λmax = 296 nm, 404 nm. Fluorescence (methanol): λmax 507 = nm, λexc = 394 nm. Fluorescence (solid): λmax = 527 nm, λexc = 404 nm. m.p. = 249–252 o  C (decomposed at 242 oC).  Synthesis of Galactose-functionalized Zinc(II) Salphen Complex (43g). Complex 43g (90%, yellow solid) was prepared by the same procedure and purification as for complex 43f.  Data for Galactose-functionalized Zinc(II) Salphen Complex (43g). 1H NMR (400 MHz, DMSO-d6) δ 8.86 (s, 2H, CH=N), 7.73 (s, 2H, aromatic CH), 7.36 (d, 2H, aromatic CH), 7.22 (t, 2H, aromatic CH), 6.70 (d, 2H, aromatic CH), 6.49 (t, 2H, aromatic CH), 5.15 (s, 2H, CH), 4.92 (t, 6H, CH), 4.61 (s, 2H, CH), 3.69 (s, 4H, CH), 3.59 (broad, 4H, OH), 3.45 (broad, 4H, OH) ppm.  13  C NMR (75.5 MHz, DMSO-d6) δ 171.9 (CH=N),  161.2, 147.0, 136.0, 134.0, 133.9, 122.9, 119.5, 112.8, 105.2 (aromatic C), 102.2, 76.1, 73.2, 70.4, 68.5, 60.9 (CH) ppm. ESI-MS: m/z = 735.3 ((M+H)+), 757.2 ((M+Na)+), 1493.4  ((2M+Na)+).  HR-ESI-MS  for  43g+Na+  (C32H34N2NaO14Zn):  757.1199  (calculated), 757.1210 (found). IR: υ = 3354 (m), 2874 (w), 1615 (s), 1601 (m), 1538 (m), 1504 (m), 1470 (s), 1441 (m), 1387 (m), 1339 (w), 1290 (m), 1207 (w), 1175 (m), 1155 (m), 1064 (s), 1047 (s), 1022 (s), 936 (w), 915 (w), 883 (w), 811 (w), 756 (s), 700 (w), 668 (w), 599 (w) cm-1. UV-vis (methanol): λmax (ε) = 242 (2.33x104), 297 (1.82x104), 343 (1.23x104), 395 (1.97x104) nm (cm-1 mol-1 L). UV-vis (solid): λmax = 291 nm, 395 nm. 190  Fluorescence (methanol): λmax = 506 nm, λexc = 395 nm. Fluorescence (solid): λmax = 525 nm, λexc = 395 nm. m.p. = 253–256 oC (decomposition started at 240 oC).  Synthesis of Acetyl-protected Glucose-functionalized Nickel(II) Salphen Complex (62b). Complex 62b was prepared by the same procedure as for complex 62a. The product was purified by chromatography on silica gel (3:1 methylene chloride/ethyl acetate) to yield complex 62b (88%, red solid).  Data for Acetyl-protected Glucose-functionalized Nickel(II) Salphen Complex (62b). 1  H NMR (300 MHz, methylene chloride-d2) δ 8.28 (s, 2H, CH=N), 7.54 (s, 2H, aromatic  CH), 7.48 (d, 2H, aromatic CH), 7.32 (t, 2H, aromatic CH), 6.99 (d, 2H, aromatic CH), 6.71 (t, 2H, aromatic CH), 5.32 (m, 4H, CH), 5.18 (m, 4H, CH), 4.24 (d, 4H, CH), 3.86 (m, 2H, CH), 2.10 (s, 6H, CH3), 2.03 (s, 6H, CH3), 2.02 (s, 6H, CH3), 2.01 (s, 6H, CH3) ppm.  13  C NMR (75.5 MHz, chloroform-d1) δ = 170.5, 170.1, 169.4, 169.3 (C(O)CH3),  166.0 (CH=N), 154.7, 146.2, 138.9, 135.4, 133.5, 121.8, 120.0, 116.2, 106.8 (aromatic C) 99.8, 72.6, 72.3, 71.3, 68.2, 61.3 (CH) 20.8, 20.7, 20.6, 20.5 ppm. MALDI-TOF-MS: m/z = 1065.4 ((M+H)+). HR-ESI-MS for 62b+H+ (C48H51N2NiO22): 1065.2287 (calculated), 1065.2299 (found). IR: υ = 1756 (m), 1611 (m), 1589 (m), 1528 (m), 1508 (m), 1464 (m), 1445 (m), 1371 (m), 1331 (w), 1289 (w), 1244 (s), 1221 (s), 1213 (s), 1188 (m), 1152 (m), 1066 (s), 1036 (s), 985 (w), 958 (w), 920 (w), 909 (w), 825 (w), 758 (m), 741 (w), 599 (m) cm-1. UV-vis (methylene chloride): λmax (ε) = 261 (8.79x104), 295 (4.67x104), 381 (6.54x104), 483 (2.22x104) nm (cm-1 mol-1 L). m.p. = 147–149 oC (decomposition started at 142 oC).  191  Synthesis of Acetyl-protected Galactose-functionalized Nickel(II) Salphen Complex (63b). Complex 63b was prepared by the same procedure as for complex 62a. The product was purified by chromatography on silica gel (3:1 methylene chloride/ethyl acetate) to yield complex 63b (82%, red solid).  Data for Acetyl-protected Galactose-functionalized Nickel(II) Salphen Complex (63b). 1H NMR (400 MHz, chloroform-d1) δ 8.12 (s, 2H, CH=N), 7.44 (s, 2H, aromatic CH), 7.41 (d, 2H, aromatic CH), 7.29 (t, 2H, aromatic CH), 7.14 (d, 2H, aromatic CH), 6.65 (t, 2H, aromatic CH), 5.45 (m, 4H, CH), 5.17 (m, 4H, CH), 4.29 (m, 2H, CH), 4.08 (m, 4H, CH), 2.20 (s, 6H, CH3), 2.13 (s, 6H, CH3), 2.01 (s, 6H, CH3), 1.94 (s, 6H, CH3) ppm.  13  C NMR (100.6 MHz, methylene chloride-d2) δ 170.8, 170.6, 170.5, 169.9  (C(O)CH3), 166.7 (CH=N), 154.8, 147.1, 139.3, 136.1, 134.1, 121.7, 120.6, 116.5, 106.5 (aromatic C) 101.0, 72.2, 71.2, 69.3, 67.7, 62.0 (CH) 21.2, 21.1, 20.0, 20.9 (CH3) ppm. MALDI-TOF-MS:  m/z  =  1065.5  ((M+H)+).  HR-ESI-MS  for  63b+Na+  (C48H50N2NaNiO22): 1087.2106 (calculated), 1087.2091 (found). IR: υ = 1747 (s), 1611 (m), 1589 (m), 1524 (m), 1508 (m), 1465 (m), 1445 (m), 1368 (m), 1334 (w), 1215 (s), 1188 (m), 1151 (m), 1126 (m), 1067 (s), 1042 (s), 952 (m), 914 (m), 850 (w), 825 (w), 754 (m), 741 (m), 710 (w), 580 (m) cm-1. UV-vis (methylene chloride): λmax (ε) = 261 (2.89x104), 296 (1.49x104), 381 (2.20x104), 483 (7.35x103) nm (cm-1 mol-1 L). m.p. = 186–188 oC (decomposition started at 177 oC).  Synthesis of Glucose-functionalized Nickel(II) Salphen Complex (54c). Complex 62b (0.160 g, 0.150 mmol) was dissolved in 120 mL of methanol, giving a red solution. Sodium methoxide (0.122 g, 2.26 mmol) was added and the reaction was stirred at room 192  temperature for 24 h. Orange precipitate was observed after stirring for several hours. The orange solid was filtered and yielded complex 54c (0.075 g, 68%, orange solid).  Data for Glucose-functionalized Nickel(II) Salphen Complex (54c). 1H NMR (400 MHz, DMSO-d6) δ 8.57 (s, 2H, CH=N), 7.88 (s, 2H, aromatic CH), 7.51 (d, 2H, aromatic CH), 7.31 (t, 2H, aromatic CH), 6.88 (d, 2H, aromatic CH), 6.66 (t, 2H, aromatic CH), 5.30 (s, 2H, CH), 5.13 (d, 4H, CH), 4.97 (d, 2H, CH), 4.88 (t, 2H, CH), 3.48 (broad, 8H, OH), 3.78 (m, 2H, CH), 3.16 (m, 2H, CH) ppm.  13  C NMR (100.6 MHz, DMSO-d6) δ  164.8 (CH=N), 155.2, 147.0, 136.7, 135.0, 134.1, 120.3, 120.2, 115.3, 104.2 (aromatic C), 101.4, 77.5, 76.7, 73.3, 70.2, 61.0 (CH) ppm. MALDI-TOF-MS: m/z = 729.5 ((M+H)+). HR-ESI-MS for 54c+Na+ (C32H34N2NaNiO14): 751.1261 (calculated), 751.1248 (found). IR: υ = 3314 (m), 2874 (w), 1610 (s), 1590 (m), 1532 (m), 1509 (m), 1465 (m), 1443 (m), 1390 (m), 1373 (m), 1321 (m), 1289 (m), 1250 (m), 1195 (m), 1187 (m), 1149 (m), 1097 (m), 1063 (s), 1037 (s), 1030 (s), 1015 (s), 990 (s), 959 (m), 920 (m), 904 (w), 886 (w), 863 (w), 848 (w), 825 (w), 759 (m), 738 (m), 656 (w), 629 (m), 587 (m) cm-1. UV-vis (DMSO): λmax (ε) = 261 (5.30x104), 294 (2.16x104), 380 (3.66x104), 478 (1.29x104) nm (cm-1 mol-1 L). m.p. = 244–247 oC (decomposition started at 240 oC).  Synthesis of Galactose-functionalized Nickel(II) Salphen Complex (54d). Complex 54d (91%, red solid) was prepared by the same procedure and purification as for complex 43f.  Data for Galactose-functionalized Nickel(II) Salphen Complex (54d). 1H NMR (400 MHz, DMSO-d6) δ 8.58 (s, 2H, CH=N), 7.93 (s, 2H, aromatic CH), 7.52 (d, 2H, aromatic 193  CH), 7.31 (t, 2H, aromatic CH), 6.88 (d, 2H, aromatic CH), 6.66 (t, 2H, aromatic CH), 5.19 (broad, 2H, CH), 4.94 (d, 6H, CH), 4.62 (broad, 2H, CH), 3.71 (s, 4H, CH), 3.67 (broad, 4H, OH), 3.58 (broad, 4H, OH) ppm. 13C NMR (100.6 MHz, DMSO-d6) δ 164.8 (CH=N), 155.2, 147.2, 136.7, 135.0, 134.1, 120.3, 120.2, 115.2, 104.4 (aromatic C), 102.1, 76.2, 73.4, 70.4, 68.5, 60.4 (CH) ppm. MALDI-TOF-MS: m/z = 729.1 ((M+H)+). HR-ESI-MS for 54d+Na+ (C32H34N2NaNiO14): 751.1261 (calculated), 751.1266 (found). IR: υ = 3385 (m), 2873 (w), 1609 (s), 1589 (m), 1532 (m), 1506 (m), 1465 (m), 1445 (m), 1373 (m), 1321 (m), 1285 (m), 1250 (w), 1190 (m), 1187 (m), 1147 (m), 1067 (s), 1044 (s), 1028 (s), 957 (m), 920 (m), 893 (w), 825 (w), 756 (s), 702 (w), 601 (m), 569 (m) cm-1. UV-vis (DMSO): λmax (ε) = 261 (5.43x104), 295 (2.19x104), 380 (3.87x104), 478 (1.36x104) nm (cm-1 mol-1 L). m.p. = 241–243 oC (decomposition started at 236 oC).  Synthesis of Acetyl-protected Glucose-functionalized Oxovanadium(IV) Salphen Complex (62c). Complex 62c was prepared by the same procedure as for complex 62a. The product was purified by chromatography on silica gel (3:1 methylene chloride/ethyl acetate) to yield complex 62c (45%, yellow solid).  Data for Acetyl-protected Glucose-functionalized Oxovanadium(IV) Salphen Complex (62c). MALDI-TOF-MS: m/z = 1073.9 ((M+H)+). HR-ESI-MS for 62c+Na+ (C48H50N2NaO23V): 1096.2142 (calculated), 1096.2172 (found). IR: υ = 1748 (s), 1608 (m), 1588 (w), 1537 (m), 1507 (m), 1468 (m), 1441 (w), 1376 (m), 1313 (w), 1217 (s), 1154 (m), 1152 (w), 1066 (s), 1036 (s), 981 (m), 919 (m), 909 (m), 859 (w), 823 (m), 760 (m), 744 (w), 610 (m), 600 (m) cm-1. UV-vis (methylene chloride): λmax (ε) = 246 (2.76x104), 319 (1.72x104), 411 (1.70x104) nm (cm-1 mol-1 L). m.p. = 149–152 oC 194  (decomposition started at 142 oC).  Synthesis of Acetyl-protected Galactose-functionalized Oxovanadium(IV) Complex Salphen (63c). Complex 63c was prepared by the same procedure as for complex 62a. The product was purified by chromatography on silica gel (1:1 methylene chloride/ethyl acetate) yielded complex 63c (58%, greenish-yellow solid).  Data for Acetyl-protected Galactose-functionalized Oxovanadium(IV) Salphen Complex (63c). MALDI-TOF-MS: m/z = 1074.6 ((M+H)+). HR-ESI-MS for 63c (C48H50N2O23V): 1073.2244 (calculated), 1073.2229 (found). IR: υ = 1749 (m), 1608 (m), 1587 (m), 1536 (m), 1509 (m), 1467 (m), 1442 (w), 1373 (m), 1313 (m), 1221 (s), 1193 (m), 1154 (m), 1125 (m), 1068 (s), 1042 (s), 981 (m), 953 (m), 918 (m), 863 (w), 824 (w), 761 (m), 745 (w), 609 (m), cm-1. UV-vis (methylene chloride): λmax (ε) = 246 (4.06x104), 319 (2.46x104), 412 (2.55x104) nm (cm-1 mol-1 L). m.p. = 182–185 oC (decomposition started at 172 oC).  Synthesis of Glucose-functionalized Oxovanadium(IV) Salphen Complex (58a). Salicylaldehyde (0.040 mL, 0.382 mmol) and vanadyl acetylacetonate (0.069 g, 0.258 mmol) were added to a solution of 4,5-bis(β-D-glucopyranosyl)phenylenediamine (46i) (0.080 g, 0.172 mmol) in ethanol (22 mL). The deep brown solution was stirred at 80 oC for 24 h. After cooling to room temperature, the product was isolated by precipitation with a mixture of petroleum ether and methylene chloride, then filtration to yield complex 58a (0.082 g, 65 %, greenish yellow solid).  195  Data for Glucose-functionalized Oxovanadium(IV) Salphen Complex (58a). ESI-MS: m/z = 737.5 ((M+H)+), 760.3 ((M+Na)+). HR-ESI-MS for 58a+Na+ (C32H34N2NaO15V): 760.1297 (calculated), 760.1287 (found). IR: υ = 3346 (m), 2874 (w), 1606 (s), 1584 (s), 1537 (s), 1507 (m), 1469 (m), 1442 (w), 1379 (s), 1337 (w), 1305 (m), 1277 (s), 1222 (w), 1194 (m), 1151 (w), 1094 (m), 1063 (s), 1038 (s), 1028 (s), 1015 (s), 981 (s), 967 (m), 919 (m), 905 (w), 858 (w), 821 (m), 753 (s), 656 (w), 633 (m), 613 (m) cm-1. UV-vis (DMSO): λmax (ε) = 254 (4.13x104), 316 (2.61x104), 355 (2.01x104), 412 (3.37x104) nm (cm-1 mol-1 L). m.p. = did not melt at 300 oC (decomposition started at 232 oC).  Synthesis of Galactose-functionalized Oxovanadium(IV) Salphen Complex (58b). Complex 58b (61%, greenish yellow solid) was prepared by the same procedure and purification as for complex 58a.  Data for Galactose-functionalized Oxovanadium(IV) Salphen Complex (58b). ESI-MS: m/z = 760.0 ((M+Na)+). HR-ESI-MS for 58b+Na+ (C32H34N2NaO15V): 760.1297 (calculated), 760.1312 (found). IR: υ = 3346 (m), 2874 (w), 1606 (s), 1586 (s), 1537 (s), 1506 (m), 1468 (m), 1440 (w), 1377 (m), 1305 (m), 1277 (m), 1191 (m), 1149 (w), 1064 (s), 1049 (s), 1032 (s), 978 (m), 967 (m), 919 (m), 889 (w), 858 (w), 822 (m), 759 (s), 700 (w), 611 (m) cm-1. UV-vis (DMSO): λmax (ε) = 254 (4.13x104), 309 (2.40x104), 355 (1.77x104), 411 (2.85x104) nm (cm-1 mol-1 L). m.p. = did not melt at 300 o  C (decomposition started at 195 oC).  196  Synthesis of Acetyl-protected Glucose-functionalized Iron(II) Salphen Complex (62d). Complex 62d was prepared by the same procedure as for complex 62a. The product was purified by chromatography on silica gel. Ethyl acetate was used to remove any impurity, followed by methanol to yield pure complex 62d (97%, brown solid).  Data for Acetyl-protected Glucose-functionalized Iron(II) Salphen Complex (62d). MALDI-TOF-MS: m/z = 1064.6 ((M+H)+). HR-ESI-MS for 62d (C48H50FeN2O22): 1062.2205 (calculated), 1062.2228 (found). IR: υ = 1748 (s), 1608 (m), 1588 (w), 1535 (w), 1505 (w), 1466 (w), 1438 (w), 1369 (m), 1316 (w), 1217 (s), 1187 (m), 1152 (w), 1065 (m), 1035 (s), 908 (w), 851 (w), 760 (w), 599 (m) cm-1. UV-vis (methylene chloride): λmax (ε) = 248 (2.53x104), 292 (2.65x104), 320 (2.13x104), 414 (1.06x104) nm (cm-1 mol-1 L). m.p. = 162–165 oC (decomposition started at 149 oC).  Synthesis of Acetyl-protected Galactose-functionalized Iron(II) Salphen Complex (63d). Complex 63d was prepared by the same procedure as for complex 62a. Chromatography on silica gel, first eluted with methylene chloride and ethyl acetate until the eluent became slight yellow to remove any impurity, followed by flushing with 1:1 ethyl acetate/acetone mixture (brown band). Rotary evaporation of the brown solution yielded complex 63d (31%, brown solid).  Data for Acetyl-protected Galactose-functionalized Iron(II) Salphen Complex (63d). MALDI-TOF-MS: m/z = 1062.8 ((M+H)+), 2124.9 ((2M+H)+). HR-ESI-MS for 63d (C48H50FeN2O22): 1062.2205 (calculated), 1062.2208 (found). IR: υ = 1747 (s), 1608 (m), 1587 (m), 1534 (m), 1504 (m), 1465 (m), 1445 (w), 1370 (m), 1317 (w), 1298 (w), 1220 197  (s), 1183 (m), 1151 (m), 1125 (w), 1067 (s), 1041 (s), 953 (w), 916 (m), 900 (w), 850 (w), 839 (w), 819 (w), 759 (m), 741 (w), 711 (w), 629 (w), 599 (m) cm-1. UV-vis (methylene chloride): λmax (ε) = 243 (2.41x104), 296 (3.03x104), 319 (2.42x104), 410 (1.18x104) nm (cm-1 mol-1 L). m.p. = 194–196 oC (decomposition started at 176 oC).  Synthesis of Glucose-functionalized Iron(II) Salphen Complex (58c). Complex 58c (65%, brown solid) was prepared by the same procedure and purification as for complex 43f.  Data for Glucose-functionalized Iron(II) Salphen Complex (58c). MALDI-TOF-MS: m/z = 727.2 ((M+H)+), 1453.6 (2M+H)+). HR-ESI-MS for 58c (C32H34FeN2O14): 726.1359 (calculated), 726.1356 (found). IR: υ = 3329 (m), 2873 (w), 1606 (s), 1586 (m), 1536 (m), 1503 (m), 1466 (m), 1440 (m), 1378 (m), 1305 (m), 1278 (m), 1183 (m), 1153 (w), 1065 (s), 1033 (s), 1013 (s), 916 (w), 846 (w), 817 (w), 757 (m), 669 (w), 583 (m) cm-1. UV-vis (DMSO): λmax (ε) = 296 (2.98x104), 344 (2.12x104), 372 (1.74x104), 418 (1.39x104) nm (cm-1 mol-1 L). m.p. = did not melt at 300 oC (decomposition started at 198 o  C).  Synthesis of Galactose-functionalized Iron(II) Salphen Complex (58d). Complex 58d (92%, brown solid) was prepared by the same procedure and purification as for complex 58a.  Data for Galactose-functionalized Iron(II) Salphen Complex (58d). ESI-MS: m/z = 726.2 ((M+H)+). HR-ESI-MS for 58d (C32H34FeN2O14): 726.1359 (calculated), 726.1363 198  (found). IR: υ = 3361 (m), 2873 (w), 1606 (s), 1590 (m), 1537 (m), 1505 (m), 1466 (m), 1444 (m), 1379 (m), 1299 (m), 1279 (m), 1184 (m), 1149 (m), 1067 (s), 1049 (s), 1032 (s), 944 (w), 917 (w), 856 (w), 817 (w), 756 (m), 700 (w), 665 (w), 600 (m) cm-1. UV-vis (DMSO): λmax (ε) = 296 (3.12x104), 342 (2.31x104), 372 (1.96x104), 417 (1.42x104) nm (cm-1 mol-1 L). m.p. = did not melt at 300 oC (decomposition started at 204 oC).  Synthesis of Acetyl-protected Glucose-functionalized Copper(II) Salphen Complex (62e). Complex 62e was prepared by the same procedure as for complex 62a. The product was purified by chromatography on silica gel (3:1 methylene chloride/ethyl acetate) to yield complex 62e (47%, yellow solid).  Data for Acetyl-protected Glucose-functionalized Copper(II) Salphen Complex (62e). MALDI-TOF-MS: m/z = 1070.4 ((M+H)+), 1092.5 ((M+Na)+). HR-ESI-MS for 62e+H+ (C48H51CuN2O22): 1070.2229 (calculated), 1070.2219 (found). IR: υ = 1751 (m), 1610 (m), 1590 (m), 1524 (m), 1504 (m), 1463 (m), 1448 (w), 1436 (w), 1375 (m), 1330 (w), 1280 (w), 1214 (s), 1183 (m), 1152 (m), 1117 (w), 1064 (m), 1034 (s), 984 (m), 959 (w), 943 (w), 916 (m), 909 (m), 852 (w), 816 (w), 757 (m), 739 (w), 702 (w), 650 (w), 626 (w), 597 (m) cm-1. UV-vis (methylene chloride): λmax (ε) = 245 (5.77x104), 311 (4.56x105), 355 (2.84x104), 407 (3.83x104), 427 (4.27x104) nm (cm-1 mol-1 L). m.p. = 168–171 oC (decomposition started at 153 oC).  Synthesis of Acetyl-protected Galactose-functionalized Copper(II) Salphen Complex (63e). Complex 63e was prepared by the same procedure as for complex 62a. The product was purified by chromatography on silica gel (9.5:0.5 ethyl acetate/acetone) and 199  yielded complex 63e (20%, greenish-yellow solid).  Data for Acetyl-protected Galactose-functionalized Copper(II) Salphen Complex (63e). MALDI-TOF-MS: m/z = 1070.3 ((M+H)+), 1092.4 ((M+Na)+). HR-ESI-MS for 63e+H+ (C48H51CuN2O22): 1070.2229 (calculated), 1070.2238 (found). IR: υ = 1747 (m), 1610 (m), 1591 (m), 1526 (m), 1505 (m), 1464 (m), 1448 (m), 1372 (m), 1328 (w), 1301 (w), 1221 (s), 1183 (m), 1153 (m), 1125 (m), 1068 (s), 1041 (s), 953 (m), 902 (m), 855 (w), 816 (w), 758 (m), 740 (m), 712 (w), 653 (w), 599 (m) cm-1. UV-vis (methylene chloride): λmax (ε) = 245 (4.06x104), 312 (3.18x105), 357 (2.05x104), 408 (2.78x104), 428 (3.03x104) nm (cm-1 mol-1 L). m.p. = 156–159 oC (decomposition started at 144 oC).  Synthesis of Glucose-functionalized Copper(II) Salphen Complex (58e). Complex 58e (81%, brownish-yellow solid) was prepared by the same procedure and purification as for complex 43f.  Data for Glucose-functionalized Copper(II) Salphen Complex (58e). ESI-MS: m/z = 734.5 ((M+H)+), 756.2 ((M+Na)+). HR-ESI-MS for 58e+Na+ (C32H34CuN2NaO14): 756.1204 (calculated), 756.1190 (found). IR: υ = 3346 (m), 2883 (w), 1610 (s), 1592 (s), 1531 (m), 1507 (s), 1466 (m), 1446 (m), 1436 (m), 1381 (m), 1311 (m), 1281 (m), 1273 (m), 1248 (m), 1220 (w), 1190 (m), 1184 (m), 1150 (m), 1126 (m), 1097 (m), 1070 (s), 1061 (s), 1040 (s), 1030 (s), 994 (s), 947 (m), 917 (m), 890 (w), 870 (w), 852 (w), 817 (w), 765 (s), 756 (m), 738 (m), 660 (w), 629 (m), 582 (m) cm-1. UV-vis (DMSO): λmax (ε) = 265 (4.64x104), 302 (3.37x104), 312 (3.20x104), 335 (2.22x104), 357 (2.35x104), 418 (3.62x104) nm (cm-1 mol-1 L). m.p. = 228–231 oC (decomposition started at 226 oC). 200  Synthesis of Galactose-functionalized Copper(II) Salphen Complex (58f). Complex 58f (92%, brown solid) was prepared by the same procedure and purification as for complex 58a.  Data for Galactose-functionalized Copper(II) Salphen Complex (58f). ESI-MS: m/z = 756.3 ((M+Na)+). HR-ESI-MS for 58f+Na+ (C32H34CuN2NaO14): 756.1204 (calculated), 756.1216 (found). IR: υ = 3323 (m), 2874 (w), 1609 (s), 1591 (s), 1531 (m), 1505 (m), 1467 (m), 1445 (m), 1436 (m), 1381 (m), 1313 (m), 1278 (m), 1249 (m), 1185 (m), 1151 (m), 1137 (m), 1067 (s), 1045 (s), 1032 (s), 951 (w), 917 (w), 891 (w), 816 (w), 761 (m), 702 (w), 595 (m) cm-1. UV-vis (DMSO): λmax (ε) = 258 (2.70x104), 304 (2.15x104), 312 (2.18x104), 335 (1.59x104), 357 (1.68x104), 418 (2.60x104) nm (cm-1 mol-1 L). m.p. = 215–218 oC (decomposition started at 212 oC).  201  6.5 References  1.  (a) Ghadiri, M. R. Adv. Mater. 1995, 7, 675. (b) Jonkheijm, P.; Hoeben, F. J. M.; Kleppinger, R.; Van Herrikhuyzen, J.; Schenning, A. P. H. J.; Meijer, E. W. J. Am. Chem. Soc. 2003, 125, 15941. (c) Engelkamp, H.; Middlebeek, S.; Nolte, R. J. M. Science 1999, 284, 785. (d) van Hameren, R.; van Buul, A. M.; Castriciano, M. A.; Villari, V.; Micali, N.; Schön, P.; Speller, S.; Monsù Scolaro, L.; Rowan, A. E.; Elemans, J. A. A. W.; Nolte, R. J. M. Nano Lett. 2008, 8, 253. (e) Kimizuka, N. Adv. Polym. Sci. 2008, 219, 1.  2.  (a) Schenning, A. P. H. J.; Meijer, E. W. Chem. Commun. 2005, 3245. (b) Schenning, A. P. H. J.; Jonkheijm, P.; Hoeben, F. J. M.; Van Herrikhuyzen, J.; Meskers, S. C. J.; Meijer, E. W.; Herz, L. M.; Daniel, C.; Silva, C.; Phillips, R. T.; Friend, R. H.; Beljonne, D.; Miura, A.; De Feyter, S.; Zdanowska, M.; Uji-i, H.; De Schryver, F. C.; Chen, Z.; Würthner, F.; Mas-Torrent, M.; den Boer, D.; Durkut, M.; Hadley, P. Syn. Met. 2004, 147, 43. (c) Kume, S.; Kuroiwa, K.; Kimizuka, N. Chem. Commun. 2006, 2442. (d) Kimizuka, N. Adv. Mater. 2000, 12, 1461.  3.  (a) Roosma, J.; Mes, T.; Leclere, P.; Palmans, A. R. A.; Meijer, E. W. J. Am. Chem. Soc. 2008, 130, 1120. (b) Koenders, M. M. J. F.; Yang, L.; Wismans, R. G.; van der Werf, K. O.; Reinhardt, D. P.; Daamen, W.; Bennink, M. L.; Dijkstra, P. J.; van Kuppevelt, T. H.; Feijen, J. Biomaterials 2009, 30, 2425. (c) Carlisle, C. R.; Coulais, C.; Namboothiry, M.; Carroll, D. L.; Hantgan, R. R.; Guthold, M. Biomaterials 2009, 30, 1205.  4.  (a) Hartgerink, J. D.; Beniash, E.; Stupp, S. I. Science 2001, 294, 1684. (b) Huang, 202  Z.-M.; Zhang, Y.-Z.; Kotaki, M.; Ramakrishna, S. Compos. Sci. Technol. 2003, 63, 2223. (c) Kenawy, E.-R.; Abdel-Hay, F. I.; El-Newehy, M. H.; Wnek, G. E. Mater. Chem. Phys. 2009, 113, 296. 5.  Tamaru, S.-i.; Nakamura, M. ; Takeuchi, M. ; Shinkai, S. Org. Lett. 2001, 3, 3631.  6.  (a) Yoza, K.; Ono, Y.; Yoshihara, K.; Akao, T.; Shinmori, H.; Takeuchi, M.; Shinkai, S.; Reinhoudt, D. N. Chem. Commun. 1998, 907. (b) Yoza, K.; Amanokura, N.; Ono, Y.; Yoshihara, K.; Akao, T.; Shinmori, H.; Takeuchi, M.; Shinkai, S.; Reinhoudt, D. N. Chem. Eur. J. 1999, 5, 2722. (c) Jung, J. H.; Shinkai, S. Top. Curr. Chem. 2004, 248, 223.  7.  Kawano, S.-i.; Tamaru, S.-i.; Fujita, N.; Shinkai, S. Chem. Eur. J. 2004, 10, 343.  8.  (a) Aoyama, Y. Chem. Eur. J. 2004, 10, 588. (b) Kim, J.; Ahn, Y.; Park, K. M.; Kim, Y.; Ko, Y. H.; Oh, D. H.; Kim, K. Angew. Chem. Int. Ed. 2007, 46, 7393.  9. (a) Patel, S. A.; Sinha, S.; Mishra, A. N.; Kamath, B. V.; Ram, R. N. J. Mol. Catal. A: Chem. 2003, 192, 53. (b) Paddock, R. L.; Nguyen, S. T. Chem. Commun. 2004, 1622. (c) Yoon, T. P.; Jacobsen, E. N. Science 2003, 299, 1691. 10. Chen, D.; Martell, A. E. Inorg. Chem. 1987, 26, 1026. 11. (a) Mao, L.; Yamamoto, K.; Zhou, W.; Jin, L. Electroanalysis 2002, 12, 72. (b) Sukwattanasinitt, M.; Nantalaksakul, A.; Potisatityuenyong, A.; Tuntulani, T.; Chailapakul, O.; Praphairakait, N. Chem. Mater. 2003, 15, 4337. 12. (a) Kleij, A. W.; Kuil, M.; Tooke, D. M.; Lutz, M.; Spek, A. L.; Reek, J. N. H. Chem. Eur. J. 2005, 11, 4743. (b) Mishra, L.; Prajapati, R.; Kimura, K.; Kobayahi, S. Inorg. Chem. Commun. 2007, 10, 1040. (c) Jung, S.; Oh, M. Angew. Chem. Int. Ed. 2008, 47, 2049. (d) Cametti, M.; Nissinen, M.; Cort, A. D.; Mandolini, L.; Rissanen, K. J. 203  Am. Chem. Soc. 2005, 127, 3831. 13. (a) Diéguez, M.; Pàmies, O.; Ruiz, A.; Díaz, Y.; Castillón, S.; Claver, C. Coord. Chem. Rev. 2004, 248, 2165. (b) Alexeev, Y. E.; Vasilchenko, I. S.; Kharisov, B. I.; Blanco, L. M.; Garnovskii, A. D.; Zhdanov, Y. A. J. Coord. Chem. 2004, 57, 1447. 14. (a) Zhao, S.; Zhao, J.; Zhao, D. Carbohydr. Res. 2007, 342, 254. (b) Borriello, C.; Del Litto, R.; Panunzi, A.; Ruffo, F. Tetrahedron: Asymmetry 2004, 15, 681. (c) Yan, S.; Klemm, D. Tetrahedron 2002, 58, 10065. 15. Storr, T.; Merkel, M.; Song-Zhao, G. X.; Scott, L. E.; Green, D. E.; Bowen, M. L.; Thompson, K. H.; Patrick, B. O.; Schugar, H. J.; Orvig, C. J. Am. Chem. Soc. 2007, 129, 7453. 16. (a) Gallant, A. J.; MacLachlan, M. J. Angew. Chem. Int. Ed. Engl. 2003, 42, 5307. (b) Ma, C. T. L.; MacLachlan, M. J. Angew. Chem. Int. Ed. 2005, 44, 4178. (c) Depree, C. V.; Beckmann, U.; Heslop, K.; Brooker, S. Dalton Trans. 2003, 3071. 17. Kleij, A. W.; Kuil, M.; Tooke, D. M.; Spek, A. L.; Reek, J. N. H. Inorg. Chem. 2007, 46, 5829. 18. Hui, J. K.-H.; Yu, Z.; MacLachlan, M. J. Angew. Chem. Int. Ed. 2007, 46, 7980. 19. Bill, R. M.; Revers, L.; Wilson, L. B. H. Protein Glycosylation, Kluwer, Boston, 1998, pp. 457–492. 20. Colourless plate (0.50 x 0.30 x 0.25 mm), a = 10.3821(4) Å, b = 16.9702(8) Å, c = 23.1117(11) Å, α = β = γ = 90°, V = 4072.0(3) Å3, space group P212121 (orthorhombic), Z = 4, mol. wt. = 860.68, T = -100.0(1) °C, μ(Mo-Kα) = 1.21 cm-1, 21309 observed (8839 unique) reflections, 541 variables, R1 = 0.0502, wR2 = 0.1431, GOF = 1.036. CCDC-740867 contains the supplementary crystallographic data. 204  These data can be obtained free of charge from the Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. 21. (a) Mathew, M.; Carty, A. J.; Palenik, G. J. J. Am. Chem. Soc. 1970, 92, 3197. (b) Hoshina, G.; Tsuchimoto, M.; Ohba, S.; Nakajima, K.; Uekusa, H.; Ohashi, Y.; Ishida, H.; Kojima, M. Inorg. Chem. 1998, 37, 142. (c) Kojima, M.; Taguchi, H.; Tsuchimoto, M.; Nakajima, K. Coord. Chem. Rev. 2003, 237, 183. (d) Bezaatpour, A.; Behzad, M.; Boghaei, D. M. J. Coord. Chem. 2009, 62, 1127. 22. (a) Kuil, M.; Puijk, I. M.; Kleij, A. W.; Tooke, D. M.; Spek, A. L.; Reek, J. N. H. Chem. Asian J. 2009, 4, 50. (b) Kuil, M.; Goudriaan, P. E.; Kleij, A. W.; Tooke, D. M.; Spek, A. L.; van Leeuwen, P. W. N. M.; Reek, J. N. H. Dalton Trans. 2007, 2311. (c) Wezenberg, S. J.; Escudero-Adán, E. C.; Benet-Buchholz, J.; Kleij, A. W. Inorg. Chem. 2008, 47, 2925. 23. (a) Kleij, A. W.; Kuil, M.; Lutz, M.; Tooke, D. M.; Spek, A. L.; Kamer, P. C. J.; van Leeuwen, P. W. N. M.; Reek, J. N. H. Inorg. Chim. Acta 2006, 359, 1807. (b) Singer, A. L.; Atwood, D. A. Inorg. Chim. Acta 1998, 277, 157. 24. (a) Kimura, T.; Shinkai, S. Chem. Lett. 1998, 1035. (b) Iwaura, R.; Hoeben, F. J. M.; Masuda, M.; Schenning, A. P. H. J.; Meijer, E. W.; Shimizu, T. J. Am. Chem. Soc. 2006, 128, 13298. 25. (a) Messmore, B. W.; Sukerkar, P. A.; Stupp, S. I. J. Am. Chem. Soc. 2005, 127, 7992. (b) Jahnke, E.; Lieberwirth, I.; Severin, N.; Rabe, J. P.; Frauenrath, H. Angew. Chem. Int. Ed. 2006, 45, 5383. (c) Jahnke, E.; Millerioux, A.-S.; Severin, N.; Rabe, J. P.; Frauenrath, H. Macromol. Biosci. 2007, 7, 136. (d) Lohr, A.; Lysetska, M.; Würthner, F. Angew. Chem. Int. Ed. 2005, 44, 5071. 205  26. (a) Okuyama, K. Connect. Tissue Res. 2008, 49, 299. (b) Rubin, N.; Perugia, E.; Goldschmidt, M.; Fridkin, M.; Addadi, L. J. Am. Chem. Soc. 2008, 130, 4602. (c) Pauling, L.; Corey, R. B. Proc. Natl. Acad. Sci. USA 1951, 37, 261. 27. (a) Amanokura, N.; Kanekiyo, Y.; Shinkai, S.; Reinhoudt, D. N. J. Chem. Soc., Perkin Trans. 2, 1999, 1995. (b) Jung, J. H.; Amaike, M.; Shinkai, S. Chem. Commun. 2000, 2343. (c) Jung, J. H.; Shinkai, S.; Shimizu, T. Chem. Rec. 2003, 3, 212. 28. Zeng, Y.; Yang, J.; Qiu, Z.; Chen, J.; Hu, C.; Zhen, P. Tetrahedron Lett. 2002, 43, 869. 29. Blom, P.; Ruttens, B.; Van Hoof, S.; Hubrecht, I.; Van der Eycken, J. J. Org. Chem. 2005, 70, 10109. 30. SAINT. Version 6.02. Bruker AXS Inc., Madison, Wisconsin, USA. 1999. 31. SADABS. Bruker Nonius area detector scaling and absorption correction – V2.05, Bruker AXS Inc., Madison, Wisconsin, USA. 32. SIR92. Altomare, A.; Cascarano, M.; Giacovazzo, C.; Guagliardi, A. J. Appl. Cryst. 1994, 26, 343. 33. Least Squares function minimized: Σw(Fo2-Fc2)2  206  CHAPTER 7 SELF-ASSEMBLY OF DINUCLEAR ZINC(II) SALPHEN COMPLEXES INTO HELICAL NANOFIBERS† 7.1 Introduction  Nanofibers are long-range-ordered, one-dimensional, nanosized supramolecular aggregates that can be linear or helical. 1 With their excellent potential for use in nanosized electronics 2 and mechanics, 3 the construction of fibrous nanostructures has been an important and attractive field for materials scientists. Also, given that one-dimensional nanostructures are widely found in biological systems (e.g., in collagen, axons, and keratin), this field has seen a rapid growth of interest in exploring and generating biomimetic fibrous structures where they might have medically relevant applications. 4  Numerous methods have been employed to make nanofibers that span diverse size ranges.  Fibers  can  be  obtained  by  supramolecular  assembly  mediated  by  hydrogen-bonding, π-π stacking, or a combination of both interactions. 5 In addition, metal-containing nanofibrils can be constructed through coordination chemistry and electrostatic interactions, in which the properties and functionalities of the materials can  †  A version of this chapter has been published as an article: Hui, J. K.-H.; MacLachlan, M. J. “Fibrous  Aggregates from Dinuclear Zinc(II) Salphen Complexes” Dalton Trans. 2010, 7310.  207  easily be tuned by altering the metal centers and modifying the ligands. 6 One-dimensional assemblies of coordination complexes are attractive for their catalytic, electronic, magnetic and optical properties. 7 Self-aggregation of building blocks through coordination chemistry and electrostatic interactions offers a robust strategy to construct diverse fibers with various degrees of control.  The MacLachlan research group has been exploiting Schiff-base chemistry to develop new macrocycles, 8,9 polymers, 10,11 and materials 12,13 that incorporate salphen moieties. 14 The salphen group can be complexed with different metals to generate functional materials. Salphen complexes containing zinc(II) have been of interest to chemists owing to their intriguing properties such as catalysis  15  and transmetalation,  16  and interesting  morphological arrangements in the field of supramolecular chemistry. 17 For instance, Oh and co-workers have prepared a zinc(II) salphen with carboxylate substitutents that led to the formation of nanofibers and further transformed into nanocubes. 18 Kleij and co-workers have reported a dinuclear zinc(II) salphen that self-organized into molecular boxes with linear ditopic ligands 4,4′-bipyridine and 1,2-bis(4-pyridyl)ethane, which can further stack into hollow channels in the solid-state. 19  Much of the interest in zinc(II) salphen complexes stems from their tendency to coordinate additional ligands to the axial sites, thereby giving the metal a coordination number of five. In fact, there are several studies that show that zinc(II) salphen complexes tend to dimerize, this being attributed to intermolecular Zn···O interactions between the zinc(II) center of a salphen unit and the phenolic oxygen of another. This property of zinc(II) salphen has been exploited for chemical sensing, whereby an analyte can 208  coordinate to the metal and induce a change in absorption or luminescence. 20  In the previous two chapters, it is illustrated that monometallic zinc(II) salphen complexes functionalized with linear and branched alkoxy substituents can act as luminescent gelators in methanol and aromatic solvents. TEM and SEM of the gels prepared from methanol revealed that the zinc(II) complexes underwent supramolecular assembly into fibers with diameters of tens of nanometers and lengths of several microns. 21 It is noteworthy that helical structures were observed in segments of the nanofibers. Modification of the peripheral substituents of the salphen complexes with carbohydrates yielded more pronounced helicity in the fibrous aggregates. 22 Experiments indicated that Zn···O interactions between the salphen groups were involved in the assembly, but it could not be confirmed whether the complexes were dimers or polymers in the fibers. Zinc(II) salphen complexes and derivatives have been used as the building units of fibrillar aggregates through metal-ligand interactions. 23  To further our understanding of the fibrillar assembly, dimetallic complexes were chosen to use as building blocks. The potential for multiple metal-ligand interactions may offer a way to modify the morphology and structures of the fibers. This chapter focuses on my studies of the synthesis, characterization and morphology of a series of new bis(zinc(II) salphen) complexes 44 (Figure 7.1). In addition, the work on tuning the morphology of the superstructures with the incorporation of ditopic 4,4′-bipyridine to dinuclear zinc(II) complex 44d will be discussed.  209  n  N  O  O  O  N  Zn O  O Zn  N  OR  RO  N  O  44a R = CH3, n = 1 44b R = C12H25, n = 1 44c R = CH3, n = 6 44d R = C12H25, n = 6  Figure 7.1. Chemical structure of dinuclear zinc(II) salphen 44.  7.2 Results and Discussion  7.2.1 Synthesis and Characterization of Dinuclear Zinc(II) Salphen Complexes 44a–d  To extend our fibrillar aggregation studies to bis(zinc(II) salphen) complexes, the complexes were designed to be bridged by an alkyl spacer between the diamine components. Thus, dinuclear zinc(II) complexes 44a–d, which differ in the length of the spacer between diaminobenzene groups, were constructed. In addition, methoxy or dodecyloxy chains are appended ortho to the bridging chain in order to promote solubility of the target complexes.  In order to make the complexes, bridged bis(diaminoaryl) compounds 68 were required to synthesize first, which can be subsequently reacted with salicylaldehyde to give 210  bis(salphen)  proligands.  Scheme  bis(2-alkoxy-4,5-diaminophenoxy)alkanes  7.1  shows 68.  the In  synthetic the  route  first  to step,  bis(2-alkoxyphenoxy)alkanes 66 were prepared in moderate yield by Williamson ether synthesis  starting  from  the  corresponding  2-alkoxyphenol  65  and  either  1,3-dibromopropane or 1,8-dibromooctane. Nitration in aqueous nitric acid afforded bis(2-alkoxy-4,5-dinitrophenoxy)alkanes 67 in 79–92% yield as yellow solids. Finally, reduction of the tetranitro compounds 67a–d using hydrazine and a palladium on carbon catalyst gave the air-sensitive tetraamino compounds 68a–d.  211  Scheme 7.1. Syntheses of compounds 65–68.  After the preparation of 68a–d was completed, subsequent reaction with salicylaldehyde in the presence of zinc(II) acetate dihydrate yielded bis(zinc salphen) complexes 44a–d. Standard characterization (NMR and IR spectroscopy, mass spectrometry) confirmed the formation of the complexes. Single crystals of bis(zinc salphen) complex 44c suitable for single crystal XRD were obtained from DMSO. 24 The solid-state structure of salphen complex 44c determined by single crystal XRD reveals that  212  both salphen moieties are essentially co-planar and the methoxy chains ortho to the bridging chain are oriented in opposite directions (Figure 7.2a). Moreover, the axial position of each metal center is occupied by one O-bound DMSO molecule, but the solvent molecules are positioned on opposite sides of the plane of the complex (Figure 7.2b). To accommodate the five-coordinate, square pyramidal geometry of the zinc centers, the salphen units are slightly distorted, with the salicylidene groups bent away from the plane of the complex (Figure 7.2c).  213  Figure 7.2. Solid-state structure of bis(zinc(II) salphen) complex 44c·2DMSO as determined by single crystal XRD. (a) Top view and (b,c) side views of the molecular structure. The hydrogen atoms have been removed for clarity. (Color legend: carbon = gray, nitrogen = nitrogen, oxygen = red, sulphur = yellow, zinc = pink) 214  ESI mass spectrometry of all four bis(zinc(II) salphen) complexes showed the molecular ion as the dominant peak, but also showed peaks corresponding to aggregates (dimers and trimers), Figure 7.3. Although quantifying the individual species by ESI mass spectrometry is not feasible, the technique is known to give a realistic snapshot of species present in solution. 25 With this piece of information, it is believed that larger aggregates of salphen complex 44 are formed in solution, similar to the case for the mononuclear analogues mentioned in Chapters 5 and 6.  Figure 7.3. ESI mass spectrum of bis(zinc(II) salphen) complex 44a.  The aggregation of the complexes in solution was further probed by 1H NMR spectroscopy. It is well-known that aggregation of zinc(II) salphen complexes can occur in 215  non-coordinating solvents such as methylene chloride and chloroform. Among the bis(zinc(II) salphen) complexes prepared, only complex 44d with an octyl bridge and dodecyloxy substituents was sufficiently soluble in deuterated methylene chloride to measure a 1H NMR spectrum. Compared to the spectra of salphen complex 44d obtained in DMSO-d6, which is a coordinating solvent that is expected to break up the aggregates, the resonance signals corresponding to aromatic protons in methylene chloride are significantly broadened and the resonances assigned to the imine protons are shifted upfield. As with monomeric zinc(II) salphen complexes, it is believed that in methylene chloride, the dimetallic complex 44d is also aggregating through Zn···O interactions between the metal center of a salphen unit and the neighboring phenolic oxygen. The broadening and upfield changes indicate self-association of the complexes in the non-coordinating solvent. 26 These effects can be diminished by adding DMSO to the sample in deuterated methylene chloride, the signals becoming sharp again and returning to near the chemical shifts observed in neat DMSO-d6. Here, the DMSO coordinates to the zinc centers and disrupts the aggregation of the zinc(II) salphen complexes. The binding of the DMSO molecules to the zinc(II) complexes is consistent with the crystal structure in Figure 7.2.  To gain a better understanding of the aggregation-disaggregation behavior, a UV-vis titration experiment was undertaken by adding DMSO (up to two equivalents) to a solution of chloroform containing zinc(II) salphen complex 44d. Spectra were recorded after each aliquot, as illustrated in Figure 7.4. The absorption band at 368 nm in chloroform was blue-shifted as DMSO was added to the sample at 0.25 equivalent intervals, to 345 nm after the addition of two equivalents of the coordinating solvent. An excess amount of DMSO was added to the sample afterward, but no further shift was observed. This is further 216  evidence that only two DMSO molecules coordinate to the zinc centers (one to each metal, as shown in Figure 7.2). In addition, the bathochromic shift of the absorption band when changing from DMSO to chloroform suggests that the bis(zinc(II) salphen) units self-assemble through J-aggregation in non-coordinating solvents.  Figure 7.4. UV-vis spectra for the titration of bis(zinc(II) salphen) complex 44d (6.05 μM in chloroform) with DMSO.  217  7.2.2 Morphological study of the Supramolecular Structures of the Dinuclear Zinc(II) Salphen Complexes 44a–d  As the ESI-MS and NMR data suggested that the complexes were assembling in solution, their assembly in the solid state were investigated by electron microscopy. Samples were prepared in methanol, chloroform and methanol/chloroform mixture, then the solutions were drop-cast onto carbon-coated grids. The samples were examined by TEM. With monometallic zinc(II) salphen complexes previously examined, nanofibers were obtained only from methanol. However, the solubility of salphen complex 44d in methanol is very poor, even at elevated temperature, and it required chloroform to dissolve it. Nanofibers were observed for all four dinuclear zinc(II) complexes in most samples and their morphologies are dependent on the lengths of the bridging hydrocarbon and peripheral alkoxy chains, and the solvent(s) used for preparation. Figure 7.5 depicts the morphologies obtained from drop-casting from methanol, chloroform and methanol/chloroform mixture.  As anticipated, TEM micrographs of bis(zinc(II) salphen) complexes 44 revealed nanofibers that are tens of nanometers in diameter and microns in length when prepared from methanol (Figures 7.5a–c), except for the zinc(II) salphen complex with octyl bridge and dodecyloxy substituents (complex 44d, Figure 7.5d). Only a cluster-like morphology was observed for salphen complex 44d, which is likely due to its poor solubility in methanol. However, with chloroform added to dissolve complex 44d in methanol (1:1 ratio) for sample preparation, the resulting drop-cast sample displayed a 218  fiber morphology with diameters of over 50 nm and lengths of several microns (Figure 7.5l). The nanofibers of complexes 44a and 44b showed a smooth surface, but when the methanol/chloroform mixtures of those two complexes were dried and examined with TEM, the surface of the fibrous structures appeared less uniform (Figures 7.5i,j). Fibers obtained from a methanol solution of salphen complex 44c have similar dimensions to those of complexes 44a and 44b (Figure 7.5c), but the surface looks different. When viewed under higher magnification, it is observed that the nanofibers were surprisingly formed from bundles of helical aggregates (Figure 7.6a). It is extrapolated that the helical organization originated from the increased flexibility of the bridge (from propyl to octyl chain), providing the complex with more freedom to twist as it underwent self-assembly through Zn···O interactions. Long fibrous networks of salphen complex 44c were observed (Figure 7.5k) for the sample drop-cast from methanol/chloroform mixture. Once again, a magnified view depicted helical bundles of nanofibrils (Figure 7.6c), in which the organization is better defined than that of the bundles obtained from pure methanol. As mentioned, a fiber morphology of salphen complex 44d was only found in the methanol/chloroform sample (Figure 7.5l). In fact, fibrous aggregates with a helical morphology could be viewed under the TEM as shown in Figure 7.6d. Further investigation was pursued on the solid-state supramolecular aggregates with chloroform alone. Since aggregation of the complexes was observed in the solution state with chloroform (NMR) and also in the solid-state when cast from a methanol/chloroform mixture or methanol, the occurrence of one-dimensional fibrous association was predicted for samples prepared from chloroform. TEM micrographs, however, displayed either ill-defined cluster morphology or short, narrow nanofibers (Figures 7.5e–g). Only the chloroform sample of salphen complex 44d exhibited the formation of nanofibers, but 219  they are narrower than those formed from methanol and methanol/chloroform mixtures (Figure 7.5h). In addition, no prominent bundle of fibers or helical arrangement was observed by electron microscopy.  220  Figure 7.5. TEM images of salphen complexes 44a–d in (a–d) methanol, (e–h) chloroform, and (i–l) methanol/chloroform mixture, respectively.  221  Figure 7.6. Higher magnification TEM images of complexes 44c and 44d in (a,b) methanol and (c,d) methanol/chloroform mixture, respectively.  The dramatic difference in morphology obtained from chloroform is rather unexpected, as self-assembly was observed by NMR spectroscopy in non-coordinating solvents. It is speculated that the zinc(II) salphen molecules were already aggregating in chloroform, and the pre-assembled aggregates are not as well structured as the ones emerging from methanol. In methanol, which can coordinate to the zinc and disrupt aggregation, the samples can better anneal and improved morphologies are thus observed. Furthermore, the polarity difference between methanol and chloroform may play a role. With the addition of methanol to chloroform, hydrophobic interactions may cause the salphen molecules to pack tighter. As a result, the modified self-association dictated by  222  the hydrophobic effects organized the salphen moieties to grow into nanofibers.  In addition to the fiber morphology being sensitive to the choice of solvent, the size of nanofibers is also affected by the lengths of the bridge and peripheral substituents. Among the four bis(zinc(II) salphen) complexes synthesized, complexes 44c and 44d with octyl bridges are roughly triple the width of those complexes with propyl bridges (complexes 44a and 44b). On the other hand, between the complexes having the same bridging chain, the ones with dodecyloxy substituents (complexes 44b and 44d) are wider (ca. 10–15 nm) than the methoxy-appended salphen complexes 44a and 44c.  It is noteworthy that the size of the bundles of nanofibers of salphen complex 44d can also be tuned by modifying the ratio of the methanol/chloroform mixture. Initially, the samples for studying supramolecular structures were prepared in 1:1 ratio of methanol/chloroform, and no precipitate was found inside capped vials left at ambient conditions. However, when the ratio changed to 3:1, a yellow precipitate slowly formed. TEM visualization of the precipitate showed bundles of nanofibers with diameters up to 200 nm and lengths of tens of microns (Figures 7.7a,b), which are much longer and wider than those bundles obtained from the 1:1 methanol/chloroform mixture. The surface of the bundles is uniform, which could also be observed by SEM (Figures 7.7c,d). The enhancement in size of the bundles with respect to the change in the methanol content of the mixture is attributed to the increase in hydrophobic effects. Additional methanol facilitates the aggregation of the hydrophobic complexes as well as individual fibers, forming bundles of fibers.  223  Figure 7.7. (a,b) TEM and (c,d) SEM images of salphen complex 44d precipitated from 1:3 chloroform/methanol mixture. The SEM samples are coated with gold/palladium for imaging.  7.2.3 Change in the Surface Morphology with the Addition of 4,4′-Bipyridine  Zinc(II) salphen complexes can behave as Lewis acids, and either coordinate Lewis bases (e.g., pyridine) to the unsaturated metal centers, or aggregate whereby the zinc of one salphen is coordinated to the phenoxy oxygen of another. 27 To date, few dinuclear zinc(II) salphen complexes have been reported.11,19,28 Kleij’s work on their version of bis(zinc(II) salphen) complexes with ditopic linear bipyridine leading to the formation of molecular boxes that can further stack into hollow channels inspired us to investigate ligation of  224  bipyridine to our zinc(II) complexes and observe the effect on the solid-state structures. Salphen complex 44d was combined with 4,4′-bipyridine (ca. one equivalent) in a mixture of methanol and chloroform, then was drop-cast onto a carbon-coated grid for TEM imaging. The micrographs showed helical fibers that are tens of nanometers wide and several microns long (Figures 7.8a,b). When the solution of salphen complex 44d and bipyridine was left in a capped vial at ambient conditions, yellow precipitate was noticed after two days. Surprisingly, when the precipitate was imaged with TEM, not only were bundles of nanofibers with significantly longer lengths (up to 30 microns) and wider diameters (up to 350 nm) detected, but they also showed a remarkable surface texture (Figures 7.8c,d). The surface of the bundles is similar to that of a coarse rope. This feature can be seen clearly by SEM (Figures 7.8e,f), which correlates with the morphology that was observed by TEM. It appears that the addition of ditopic 4,4′-bipyridine leads to a different aggregation mode of metal-ligand coordination. Instead of the salphen molecules linking together only through Zn···O interactions, they can also be bridged by 4,4′-bipyrdine in the fibers.  225  Figure 7.8. (a,b) TEM images of complex 44d with 4,4′-bipyridine drop-cast from methanol/chloroform mixture. (b) is the magnified view of (a). (c,d) TEM and (e,f) SEM images of the yellow precipitate. The SEM samples are coated with gold/palladium for imaging. (The short fibers in the background of (d–f) are from the fibrous aggregates that were still in solution before drop-casting the precipitate onto the grid.)  To prove that the product of bis(zinc(II) salphen) complex 44d with 4,4′-bipyridine is a new species rather than a phase-separated mixture of the starting materials, the yellow precipitate isolated from solution was analyzed by powder XRD for comparison with 226  independent samples of salphen complex 44d and 4,4′-bipyridine prepared in the same way. Figure 7.9 shows the powder XRD patterns of these three samples. 4,4′-Bipyridine is a microcrystalline powder with no peaks at 2θ < 10º. PXRD of complex 44d showed only broad diffracion peaks corresponding to (10), (20), and (30) reflections of a lamellar organization with an interlayer separation of ca. 32 Å. This suggests that the molecules are organized in a way that allows interdigitation of the dodecyloxy chains from the salphen complexes. The powder XRD pattern of salphen complex 44d with 4,4′-bipyridine showed a similar lamellar diffraction pattern to that of salphen complex 44d, with an interlayer spacing of ca. 33 Å. Notably, the peaks are much sharper than in the case of pure salphen complex 44d and additional features are observed at 10, 5.7, 5.0, and 3.5 Å d-spacing. It appears that incorporation of 4,4′-bipyridine into the assembly enhances the organization of the bis(zinc(II) salphen) molecules, leading to improved crystallinity. The 1H NMR spectrum of the yellow precipitate of salphen complex 44d with 4,4′-bipyridine (nanofibers with coarse rope morphology) shows both components and by comparing the integration of their aromatic peaks, the ratio of salphen complex 44d to 4,4′-bipyridine was calculated to be 2.5:1 in the fibers.  227  Figure 7.9. Powder XRD patterns of the precipitate obtained when complex 44d is combined with 4,4′-bipyridine (top), complex 44d (middle), and 4,4′-bipyridine (bottom).  7.3 Conclusions  A series of dinuclear zinc(II) salphen complexes having two salphen units connected by a flexible alkyl bridge and functionalized with alkoxy substituents has been prepared. TEM studies of the solid-state supramolecular structures of the complexes prepared from methanol, chloroform and methanol/chloroform mixtures showed nanofibers that extend several microns in length. Surprisingly, the micrographs of the two zinc(II) complexes with octyl bridges, complexes 44c and 44d, revealed helical arrangements. In addition, the nanofibers organized into bundles and could be widened by increasing the methanol content in the methanol/chloroform mixture, leading to stronger hydrophobic effects. 228  Further study of the aggregation behavior with the introduction of linear bridging ligand, 4,4′-bipyridine, to salphen complex 44d revealed bundles of nanofibers with a coarse-rope-like surface texture. These results show that the fibrillar aggregation of bis(zinc(II) salphen) complexes is sensitive to solvent, substituents, and the bridging group, and that additives (e.g., 4,4′-bipyridine) can strongly influence the morphology of the fibers. This control in the assembly process is important if zinc(II) salphen complexes are to be used for directing the assembly of more sophisticated structures.  7.4 Experimental  General procedures: All reactions were carried out under nitrogen atmosphere by means of standard Schlenk techniques unless otherwise stated. Tetrahydrofuran was distilled from sodium/benzophenone under nitrogen. Ethanol and DMF were purged with nitrogen gas and dried over molecular sieves before use. Deuterated solvents were obtained from Cambridge Isotope Laboratories, Inc.. All reagents were used as received unless otherwise stated.  1,8-Dibromooctane,  1,3-dibromopropane,  hydrazine,  salicylaldehyde  tetra(n-butyl)ammmonium bromide and zinc(II) acetate dihydrate were obtained from Aldrich. Palladium on carbon was obtained from Pressure Chemical. Nitric acid and potassium carbonate were obtained from Fisher. 2-Dodecyloxyphenol (65b) was prepared by a literature method. 29  Equipment. 300 MHz 1H and 75.5 MHz  13  C NMR spectra were recorded on a Bruker  AV-300 spectrometer. 400 MHz 1H and 100.6 MHz 13C NMR spectra were recorded on a  229  Bruker AV-400 spectrometer. UV-vis spectra were obtained of samples dissolved in methylene chloride or dimethyl sulfoxide on a Varian Cary 5000 UV-vis/near-IR spectrometer using a 1 cm cuvette. IR spectra were obtained using a Thermo Scientific Nicolet 6700 FT-IR spectrometer equipped with a diamond Attenuated Total Reflectance. Mass spectra and elemental analyses were obtained at the UBC Microanalytical Services Laboratory. ESI mass spectra were obtained on a Bruker Esquire-LC ion trap mass spectrometer equipped with an electrospray ion source. HR-ESI mass spectra were obtained on a Micromass LCT TOF mass spectrometer equipped with an electrospray ion source. Samples for both ESI and HR-ESI were analyzed in methanol, DMSO/methanol mixture or methylene chloride/methanol mixture at 1 μM. Angiotensin I, angiotensin III, asn-arg-asn-phe-leu-arg-phe amide and substance P were used as the references for HR-ESI. EI and high-resolution electron impact (HR-EI) mass spectra were recorded on a Kratos MS-50 double focusing sector mass spectrometer equipped with an EI ion source. Elemental analyses were obtained on a Carlo Erba Elemental Analyzer EA 1108. Melting points were obtained on a Fisher-John’s melting point apparatus. TEM and SEM images were obtained at the UBC BioImaging Facility on a Hitachi H7600 transmission electron microscope and a Hitachi S-4700 field emission scanning electron microscope, respectively. The TEM and SEM samples were prepared by dissolving the compounds in methanol, chloroform or methanol/chloroform mixture and drop-casting onto carbon-coated grids and aluminum stubs, respectively. Powder XRD data were recorded on a D8 Advance powder X-ray diffractometer by drop-casting the samples onto silicon plates.  More Information on Crystallography. Crystals of complex 44c suitable for X-ray 230  diffraction were grown from DMSO. All measurements were made on a Bruker X8 APEX CCD diffractometer with graphite monochromated Mo-Kα radiation (λ = 0.71069 Å). The data were collected at a temperature of -100.0 ± 0.1°C to a maximum 2θ value of 53°. Of the 51720 reflections that were collected, 8061 were unique (Rint = 0.0485); equivalent reflections were merged. The structure was solved by direct methods and the refinement was performed using SHELXL-97. 30 One DMSO molecule was disordered over two positions with a shared oxygen atom. The disordered DMSO was left isotropic and all atoms in it excluding the shared oxygen were modeled with half occupancy. All other atoms were refined anisotropically. Hydrogen atoms were included at fixed positions. CCDC-771868 contains the supplementary crystallographic data. These data can be obtained free of charge from the Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.  Synthesis of 1,3-Bis(2-methoxyphenoxy)propane (66a). Potassium carbonate (12.57 g, 90.9 mmol), tetra(n-butyl)ammonium bromide (a spatula tip) and guaiacol (65a) (10.00 mL, 90.9 mmol) were added to a DMF solution (200 mL) of 1,3-dibromopropane (3.72 mL, 36.4 mmol). The mixture was stirred at 80 oC for 5 d under nitrogen. After cooling to room temperature, the gray mixture was poured into 600 mL of water, giving a white precipitate. Isolation of the solid by filtration, followed by recrystallization from methanol yielded compound 66a (6.53 g, 62%, white crystals).  Data for 1,3-Bis(2-methoxyphenoxy)propane (66a). 1H NMR (400 MHz, chloroform-d1) δ 6.94–6.85 (m, 8H, aromatic CH), 4.23 (t, 4H, OCH2), 3.83 (s, 6H, OCH3), 2.34 (quintet, 2H, CH2) ppm. 13C NMR (100.6 MHz, chloroform-d1) δ 149.8, 148.6, 121.4, 121.1, 113.8, 231  112.1 (aromatic C) 66.0 (OCH2), 56.1 (OCH3), 29.5 (CH2) ppm. EI-MS: m/z = 288 (M+). IR: υ = 3007 (w), 2955 (w), 2938 (w), 2931 (w), 2882 (w), 2837 (w), 1591 (m), 1508 (s), 1464 (m), 1456 (m), 1438 (m), 1400 (w), 1385 (w), 1368 (w), 1328 (m), 1289 (w), 1250 (s), 1223 (s), 1184 (s), 1163(w), 1151 (w), 1122 (s), 1069 (m), 1054 (m), 1020 (s), 995 (m), 978 (m), 903 (m), 849 (w), 831 (w), 784 (m), 773 (w), 740 (s), 613 (w) cm-1. UV-vis (methylene chloride): λmax (ε) = 277 (5.59x103) nm (cm-1 mol-1 L). Anal. Calc’d (%) for 66a (C17H20O4): C 70.81, H 6.99; Found: C 70.55, H 6.95. m.p. = 110–111 oC.  Synthesis of 1,3-Bis(2-dodecyloxyphenoxy)propane (66b). Compound 66b (63%, white solid) was prepared by the same procedure and purification as for compound 66a.  Data for 1,3-Bis(2-dodecyloxyphenoxy)propane (66b).  1  H NMR (300 MHz,  chloroform-d1) δ 6.97–6.83 (m, 8H, aromatic CH), 4.21 (t, 4H, OCH2), 3.95 (t, 4H, OCH2), 2.30 (quintet, 2H, CH2), 1.77 (quintet, 4H, CH2), 1.42 (m, 4H, CH2), 1.24 (broad, 32H, CH2), 0.86 (t, 6H, CH3) ppm. 13C NMR (100.6 MHz, chloroform-d1) δ 149.5, 149.2, 121.5, 121.2, 114.5, 114.3 (aromatic C), 69.5, 66.2 (OCH2), 32.1, 29.9, 29.9, 29.9, 29.8, 29.7, 296, 29.6, 26.3, 22.9 (CH2), 14.3 (CH3) ppm. EI-MS: m/z = 596 (M+). IR: υ = 2925 (w), 2953 (m), 2912 (m), 2873 (m), 2845 (m), 1594 (m), 1515 (m), 1505 (m), 1467 (w), 1464 (m), 1452 (m), 1435 (w), 1422 (w), 1387 (m), 1369 (w), 1358 (w), 1329 (m), 1287 (m), 1255 (s), 1220 (s), 1198 (w), 1186 (w), 1151 (w), 1122 (s), 1067 (m), 1054 (m), 1045 (w), 1032 (w), 1021 (w), 1000 (m), 977 (m), 959 (w), 917 (w), 905 (w), 894 (w), 868 (w), 851 (w), 823 (w), 795 (w), 753 (w), 727 (s), 609 (w) cm-1. UV-vis (methylene chloride): λmax (ε) = 278 (4.58x103) nm (cm-1 mol-1 L). Anal. Calc’d (%) for 66b (C39H64O4): C 78.47, H 10.81; Found: C 78.63, H 10.75. m.p. = 73–75 oC. 232  Synthesis of 1,8-Bis(2-methoxyphenoxy)octane (66c). Compound 66c (58%, white solid) was prepared by the same procedure and purification as for compound 66a.  Data for 1,8-Bis(2-methoxyphenoxy)octane (66c). 1H NMR (400 MHz, chloroform-d1) δ 6.87 (s, 8H, aromatic CH), 3.99 (t, 4H, OCH2), 3.84 (s, 6H, OCH3), 1.83 (quintet, 4H, CH2), 1.44 (quintet, 4H, CH2), 1.39–1.36 (m, 4H, CH2) ppm.  13  C NMR (100.6 MHz,  chloroform-d1) δ 149.6, 148.8, 121.0, 121.0, 113.3, 112.0 (aromatic C) 69.1 (OCH2), 56.1 (OCH3), 29.5, 29.4, 26.1 (CH2) ppm. EI-MS: m/z = 358 (M+). IR: υ = 2998 (w), 2934 (m), 2919 (m), 2892 (w), 2868 (w), 2851 (w), 2841 (m), 1588 (m), 1502 (m), 1462 (m), 1455 (m), 1439 (m), 1427 (w), 1383 (m), 1330 (m), 1288 (w), 1281 (w), 1248 (m), 1220 (s), 1177 (m), 1157 (m), 1119 (s), 1062 (m), 1052 (m), 1031 (m), 1009 (m), 995 (m), 934 (m), 910 (w), 827 (m), 780 (m), 749 (s), 727 (s), 607 (w) cm-1. UV-vis (methylene chloride): λmax (ε) = 277 (5.05x103) nm (cm-1 mol-1 L). Anal. Calc’d (%) for 66c (C22H30O4): C 73.71, H 8.44; Found: C 73.34, H 8.40. m.p. = 83–86 oC.  Synthesis of 1,8-Bis(2-dodecyloxyphenoxy)octane (66d). Compound 66d (55%, white solid) was prepared by the same procedure and purification as for compound 66a.  Data  for  1,8-Bis(2-dodecyloxyphenoxy)octane  (66d).  1  H  NMR  (300  MHz,  chloroform-d1) δ 6.86 (s, 8H, aromatic CH), 3.97 (t, 8H, OCH2), 1.79 (quintet, 8H, CH2), 1.44 (quintet, 8H, CH2), 1.39 (m, 8H, CH2), 1.24 (broad, 28H, CH2), 0.86 (t, 6H, CH3) ppm.  13  C NMR (100.6 MHz, chloroform-d1) δ 149.5, 149.5, 121.3, 121.2, 114.4, 114.4  (aromatic C), 69.5 (OCH2), 32.1, 29.9, 29.9, 29.9, 29.7, 29.6, 29.6, 26.3, 26.2, 22.9 (CH2), 14.3 (CH3) ppm. EI-MS: m/z = 666 (M+). IR: υ = 2954 (w), 2947 (w), 2914 (m), 2871 (w), 233  2848 (m), 1594 (m), 1517 (m), 1506 (s), 1467 (m), 1452 (m), 1432 (w), 1388 (m), 1332 (w), 1293 (w), 1281 (w), 1256 (s), 1221 (s), 1198 (m), 1162 (w), 1144 (w), 1121 (m), 1063 (m), 1023 (m), 1011 (m), 992 (w), 958 (w), 928 (w), 905 (w), 893 (w), 831 (w), 796 (w), 754 (w), 729 (s), 618 (w), 600 (w) cm-1. UV-vis (methylene chloride): λmax (ε) = 278 (4.90x103) nm (cm-1 mol-1 L). Anal. Calc’d (%) for 66d (C44H74O4): C 79.22, H 11.18; Found: C 78.94, H 11.02. m.p. = 68–70 oC  Synthesis of 1,3-Bis(2-methoxy-4,5-dinitrophenoxy)propane (67a). Compound 67a (5.58 g, 19.4 mmol) was added to 300 mL of nitric acid, giving a yellow solution. The reaction was stirred at 80 oC for 20 h during which time a yellow precipitate formed. After cooling to room temperature, the mixture was poured into 800 mL of water, then isolated by filtration. Recrystallization of the crude product from EtOH yielded compound 67a (7.17 g, 79%, yellow solid).  Data for 1,3-Bis(2-methoxy-4,5-dinitrophenoxy)propane (67a). 1H NMR (300 MHz, chloroform-d1) δ 7.36 (s, 2H, aromatic CH), 7.30 (s, 2H, aromatic CH), 4.33 (t, 4H, OCH2), 3.97 (s, 6H, OCH3), 2.45 (quintet, 2H, CH2) ppm.  13  C NMR (100.6 MHz, DMSO-d6) δ  152.0, 150.8, 136.0, 135.8, 108.6, 107.9 (aromatic C), 66.5 (OCH2), 57.1 (OCH3), 27.9 (CH2) ppm. EI-MS: m/z = 468 (M+). IR: υ = 3124 (w), 3068 (w), 2980 (w), 2897 (w), 2860 (w), 1589 (m), 1530 (s), 1469 (m), 1460 (m), 1444 (m), 1402 (w), 1370 (m), 1332 (s), 1281 (s), 1229 (s), 1194 (m), 1181 (m), 1130 (m), 1043 (s), 1016 (m), 1003 (m), 980 (m), 940 (m), 866 (s), 826 (m), 814 (m), 804 (m), 798 (s), 780 (m), 751 (m), 720 (m), 659 (m), 623 (m) cm-1. UV-vis (DMSO): λmax (ε) = 276 (7.84x103), 344 (7.18x103) nm (cm-1 mol-1 L). Anal. Calc’d (%) for 67a (C17H16N4O12): C 43.60, H 3.44, N 11.96; Found: C 43.52, H 234  3.28, N 11.81. m.p. = 224–227 oC.  Synthesis of 1,3-Bis(2-dodecyloxy-4,5-dinitrophenoxy)propane (67b). Compound 67b (80%, yellow solid) was prepared by the same procedure and purification as for compound 67a.  Data for 1,3-Bis(2-dodecyloxy-4,5-dinitrophenoxy)propane (67b). 1H NMR (300 MHz, chloroform-d1) δ 7.33 (s, 2H, aromatic CH), 7.26 (s, 2H, aromatic CH), 4.31 (t, 4H, OCH2), 4.06 (t, 4H, OCH2), 2.43 (quintet, 2H, CH2), 1.83 (quintet, 4H, CH2), 1.41 (m, 4H, CH2), 1.23 (broad, 32H, CH2), 0.86 (t, 6H, CH3) ppm. 13C NMR (100.6 MHz, DMSO-d6) δ 151.6, 150.9, 136.3, 135.4, 108.9, 108.6 (aromatic C), 69.8, 66.3 (OCH2), 31.2, 29.0, 28.9, 28.9, 28.7, 28.4, 28.0, 27.8, 25.2, 22.0 (CH2), 13.8 (CH3) ppm. EI-MS: m/z = 776 (M+). IR: υ = 2920 (m), 2875 (w), 2848 (m), 1594 (m), 1532 (s), 1514 (s), 1463 (m), 1369 (m), 1339 (m), 1282 (s), 1220 (s), 1178 (w), 1094 (w), 1062 (m), 1042 (m), 1034 (m), 982 (w), 972 (m), 951 (w), 914 (w), 890 (w), 870 (m), 853 (w), 802 (w), 780 (w), 750 (m), 720 (m), 664 (m) cm-1. UV-vis (methylene chloride): λmax (ε) = 271 (1.24x104), 336 (1.08x104) nm (cm-1 mol-1 L). Anal. Calc’d (%) for 67b (C39H60N4O12): C 60.29, H 7.78, N 7.21; Found: C 59.91, H 7.60, N 7.46. m.p. = 64–66 oC.  Synthesis of 1,8-Bis(2-methoxy-4,5-dinitrophenoxy)octane (67c). Compound 67c (83%, yellow solid) was prepared by the same procedure and purification as for compound 67a.  Data for 1,8-Bis(2-methoxy-4,5-dinitrophenoxy)octane (67c). 1H NMR (300 MHz, chloroform-d1) δ 7.31 (s, 2H, aromatic CH), 7.28 (s, 2H, aromatic CH), 4.10 (t, 4H, OCH2), 235  3.98 (s, 6H, OCH3), 1.88 (quintet, 4H, CH2), 1.45 (broad, 8H, CH2), 0.86 (t, 6H, CH3) ppm. 13  C NMR (100.6 MHz, DMSO-d6) δ 151.8, 151.2, 136.0, 135.6, 108.3, 107.8 (aromatic C),  69.8 (OCH2), 57.1 (OCH3), 28.5, 28.1, 25.3 (CH2) ppm. EI-MS: m/z = 538 (M+). IR: υ = 3120 (w), 3092 (w), 3071 (w), 2946 (w), 1587 (m), 1526 (s), 1465 (s), 1441 (w), 1372 (m), 1355 (m), 1332 (m), 1281 (s), 1258 (m), 1229 (s), 1190 (m), 1043 (s), 1012 (m), 979 (m), 872 (m), 855 (w), 814 (m), 797 (m), 751 (m), 733 (w), 721 (m), 664 (m), 621 (w), 600 (w) cm-1. UV-vis (DMSO): λmax (ε) = 277 (6.01x103), 348 (5.70x103) nm (cm-1 mol-1 L). Anal. Calc’d (%) for 67c (C22H26N4O12): C 49.07, H 4.87, N 10.41; Found: C 49.33, H 4.72, N 10.19. m.p. = 201–204 oC.  Synthesis of 1,8-Bis(2-dodecyloxy-4,5-dinitrophenoxy)octane (67d). Compound 67d (92%, yellow solid) was prepared by the same procedure and purification as for compound 67a.  Data for 1,8-Bis(2-dodecyloxy-4,5-dinitrophenoxy)octane (67d). 1H NMR (300 MHz, chloroform-d1) δ 7.27 (s, 4H, aromatic CH), 4.08 (t, 8H, OCH2), 1.85 (quintet, 8H, CH2), 1.42 (broad, 8H, CH2), 1.24 (broad, 36H, CH2), 0.85 (t, 6H, CH3) ppm. 13C NMR (100.6 MHz, DMSO-d6) δ 152.0, 151.9, 136.8, 136.7, 108.2, 108.2 (aromatic C), 70.4, 70.3 (OCH2), 32.1, 29.9, 29.9, 29.8, 29.8, 29.6, 29.4, 29.4, 28.9, 26.0, 26.0, 22.9 (CH2), 14.3 (CH3) ppm. EI-MS: m/z = 846 (M+). IR: υ = 2918 (m), 2861 (w), 2851 (m), 1587 (m), 1519 (s), 1468 (m), 1376 (m), 1355 (m), 1334 (m), 1292 (m), 1223 (s), 1184 (w), 1068 (w), 1039 (m), 1001 (w), 986 (w), 970 (w), 954 (w), 917 (w), 876 (m), 816 (m), 800 (w), 752 (m), 720 (w), 664 (w), 629 (w) cm-1. UV-vis (methylene chloride): λmax (ε) = 273 (1.81x104), 338 (1.54x104) nm (cm-1 mol-1 L). Anal. Calc’d (%) for 67d (C44H70N4O12): C 62.39, H 236  8.33, N 6.61; Found: C 62.13, H 8.20, N 6.78. m.p. = 91–93 oC.  Synthesis of 1,3-Bis(4,5-diamino-2-methoxyphenoxy)propane (68a). Compound 67a (3.00 g, 6.41 mmol) was dissolved in ethanol (200 mL) and the solution was purged with nitrogen for 15 mins. Palladium on carbon (2 spatula tips) and hydrazine (5 mL, 103.1 mmol) were then added to the flask under nitrogen. The resulting mixture was stirred at 90 o  C for 20 h until the solution became clear and colorless. Raney Ni (a spatula tip) was  added to the reaction flask and stirred at 90 oC for 2 h in order to remove any unreacted hydrazine. After cooling the reaction mixture to room temperature, the catalyst was removed by filtration through a Schlenk frit and a colorless filtrate was obtained. The solvent was then removed under vacuum and yielded air-sensitive compound 68a (2.17 g, 97%, white solid). This compound was ~95% pure (1H NMR) and was used without further purification. Attempts to remove colored impurities resulted in further decomposition, so it was best to purify at the next stage.  Data for 1,3-Bis(4,5-diamino-2-methoxyphenoxy)propane (68a). 1H NMR (400 MHz, chloroform-d1) δ 6.40 (s, 2H, aromatic CH), 6.34 (s, 2H, aromatic CH), 4.10 (t, 4H, OCH2), 3.74 (s, 6H, OCH3), 3.16 (s, 8H, NH2), 2.20 (quintet, 2H, CH2) ppm.  13  C NMR (100.6  MHz, DMSO-d6) δ 141.5, 139.9, 129.1, 128.6, 104.9, 103.1 (aromatic C), 66.7 (OCH2), 56.7 (OCH3), 29.5 (CH2) ppm. EI-MS: m/z = 348 (M+). HR-EI-MS for 68a (C17H24N4O4): 348.1798 (calculated), 348.1795 (found).  Synthesis of 1,3-Bis(4,5-diamino-2-dodecyloxyphenoxy)propane (68b). Compound 68b (93%, yellow sticky solid) was prepared by the same procedure and purification as for 237  compound 68a. This compound was ~90% pure (1H NMR) and was used without further purification. Attempts to obtain a pure product resulted in further decomposition, so it was best to purify at the next stage.  Data for 1,3-Bis(4,5-diamino-2-dodecyloxyphenoxy)propane (68b). 1H NMR (300 MHz, chloroform-d1) δ 6.36 (s, 2H, aromatic CH), 6.35 (s, 2H, aromatic CH), 4.08 (t, 4H, OCH2), 3.85 (t, 4H, OCH2), 3.13 (s, 8H, NH2), 2.15 (quintet, 2H, CH2), 1.70 (quintet, 4H, CH2), 1.36 (m, 4H, CH2), 1.22 (broad, 32H, CH2), 0.85 (t, 6H, CH3) ppm. 13C NMR (100.6 MHz, DMSO-d6) δ 140.9, 140.5, 129.3, 129.1, 105.4, 105.1 (aromatic C), 69.9, 67.1 (OCH2), 31.3, 29.7, 29.2, 29.1, 29.1, 29.0, 28.9, 28.8, 25.6, 22.1 (CH2), 13.9 (CH3) ppm. EI-MS: m/z = 656 (M+). HR-EI-MS for 68b (C39H68N4O4): 656.5241 (calculated), 656.5246 (found).  Synthesis of 1,8-Bis(4,5-diamino-2-methoxyphenoxy)octane (68c). Compound 68c (89%, yellow solid) was prepared by the same procedure and purification as for compound 68a. This compound was ~95% pure (1H NMR) and was used without further purification. Attempts to obtain a pure product resulted in further decomposition, so it was best to purify at the next stage.  Data for 1,8-Bis(4,5-diamino-2-methoxyphenoxy)octane (68c). 1H NMR (400 MHz, chloroform-d1) δ 6.38 (s, 2H, aromatic CH), 6.36 (s, 2H, aromatic CH), 3.89 (t, 4H, OCH2), 3.77 (s, 6H, OCH3), 3.21 (s, 8H, NH2), 1.77 (quintet, 4H, CH2), 1.48–1.33 (m, 8H, CH2) ppm.  13  C NMR (100.6 MHz, DMSO-d6) δ 141.5, 140.1, 128.9, 128.6, 104.8, 103.2  (aromatic C), 69.6 (OCH2), 56.7 (OCH3), 29.2, 28.8, 25.6 (CH2) ppm. EI-MS: m/z = 418 238  (M+). HR-EI-MS for 68c (C22H34N4O4): 418.2580 (calculated), 418.2579 (found).  Synthesis of 1,8-Bis(4,5-diamino-2-dodecyloxyphenoxy)octane (68d). Compound 68d (95%, yellow solid) was prepared by the same procedure and purification as for compound 68a. This compound was ~95% pure (1H NMR) and was used without further purification. Attempts to obtain a pure product resulted in further decomposition, so it was best to purify at the next stage.  Data for 1,8-Bis(4,5-diamino-2-dodecyloxyphenoxy)octane (68d). 1H NMR (300 MHz, chloroform-d1) δ 6.35 (s, 4H, aromatic CH), 3.86 (t, 8H, OCH2), 3.20 (s, 8H, NH2), 1.72 (quintet, 8H, CH2), 1.41 (m, 8H, CH2), 1.38–1.24 (m, 36H, CH2), 0.86 (t, 6H, CH3) ppm. 13  C NMR (100.6 MHz, DMSO-d6) δ 140.8, 140.8, 129.1, 129.1, 105.2, 105.1 (aromatic C),  70.0, 69.9 (OCH2), 31.3, 29.4, 29.3, 29.1, 29.0, 29.0, 28.9, 28.7, 25.7, 25.7, 22.1 (CH2), 13.9 (CH3) ppm. EI-MS: m/z = 726 (M+). HR-EI-MS for 68d (C44H78N4O4): 726.6023 (calculated), 726.6028 (found).  Synthesis of Bis(Zinc(II) Salphen) Complex 44a. Compound 68a (0.300 g, 0.861 mmol) was dissolved in tetrahydrofuran (60 mL) under nitrogen. Salicylaldehyde (0.38 mL, 3.62 mmol) and zinc(II) acetate dihydrate (0.473 g, 2.15 mmol) were added, giving a yellow solution. The solution was stirred at 90 oC for 20 h and a yellow precipitate was observed. After cooling to room temperature, the mixture was poured into 400 mL of water and the yellow  solid  was  isolated  by  filtration.  Recrystallization  from  a  methylene  chloride/methanol mixture yielded bis(zinc(II) salphen) complex 44a (0.738 g, 96%, yellow solid). 239  Data for Bis(Zinc(II) Salphen) Complex 44a. 1H NMR (400 MHz, DMSO-d6) δ 9.00 (s, 2H, CH=N), 8.98 (s, 2H, CH=N), 7.57 (s, 2H, aromatic CH), 7.50 (s, 2H, aromatic CH), 7.42 (d, 4H, aromatic CH), 7.21 (t, 4H, aromatic CH), 6.70 (d, 4H, aromatic CH), 6.51 (t, 4H, aromatic CH), 4.35 (t, 4H, OCH2), 3.91 (s, 6H, OCH3), 2.33 (quintet, 2H, CH2) ppm. 13  C NMR (100.6 MHz, DMSO-d6) δ 171.8 (CH=N), 160.7, 149.2, 148.2, 135.8, 133.7,  132.9, 132.7, 122.9, 119.7, 119.6, 112.8, 100.8, 99.7 (aromatic C), 65.6 (OCH2), 56.1 (OCH3), 28.8 (CH2) ppm. ESI-MS: 891.0 ((M+H)+), 913.0 ((M+Na)+), 1780.9 ((2M+H)+), 1806.9 ((2M+Na)+), 2694.8 ((3M+Na)+). HR-ESI-MS for 44a+Na+ (C45H36N4NaO8Zn2): 911.1014 (calculated), 911.0995 (found). IR: υ = 3011 (w), 2929 (w), 2896 (w), 1610 (s), 1531 (m), 1504 (m), 1462 (s), 1439 (m), 1380 (m), 1344 (w), 1314 (m), 1264 (m), 1246 (m), 1213 (w), 1174 (m), 1150 (m), 1130 (w), 1109 (m), 1047 (w), 1033 (w), 1017 (m), 982 (w), 960 (w), 931 (w), 912 (m), 837 (m), 806 (w), 751 (s), 736 (s), 680 (w), 616 (w) cm-1. UV-vis (DMSO): λmax (ε) = 301 (6.90x104), 337 (4.73x104), 354 (5.56x104), 407 (1.11x105) nm (cm-1 mol-1 L). m.p. = did not melt at 300 oC.  Synthesis of Bis(Zinc(II) Salphen) Complex 44b. Bis(zinc(II) salphen) complex 44b (81%, yellow solid) was prepared by the same procedure and purification as for bis(zinc(II) salphen) complex 44a.  Data for Bis(Zinc(II) Salphen) Complex 44b. 1H NMR (400 MHz, DMSO-d6) δ 8.96 (s, 2H, CH=N), 8.95 (s, 2H, CH=N), 7.57 (s, 2H, aromatic CH), 7.48 (s, 2H, aromatic CH), 7.39 (t, 4H, aromatic CH), 7.20 (m, 4H, aromatic CH), 6.69 (d, 4H, aromatic CH), 6.49 (t, 4H, aromatic CH), 4.37 (t, 4H, OCH2), 4.07 (t, 4H, OCH2), 2.29 (quintet, 2H, CH2), 1.70 (quintet, 4H, CH2), 1.38 (quintet, 4H, CH2), 1.20 (m, 8H, CH2), 1.12 (broad, 24H, CH2), 240  0.80 (t, 6H, CH3) ppm. 13C NMR (100.6 MHz, DMSO-d6) δ 171.6 (CH=N), 160.8, 160.6, 148.9, 148.5, 135.8, 135.7, 133.7, 133.6, 133.2, 132.8, 122.9, 119.6, 101.6, 101.1 (aromatic C), 68.8, 65.8 (OCH2), 31.3, 29.1, 19.0, 29.0, 28.7, 25.6, 22.1 (CH2), 13.9 (CH3) ppm. ESI-MS: 1199.4 ((M+H)+), 1223.4 ((M+Na)+), 1239.4 ((M+K)+), 2426.9 ((2M+Na)+), 2437.8 ((2M+K)+), 3623.1 ((3M+Na)+). HR-ESI-MS for 44b+H+ (C67H81N4NaO8Zn2): 1197.4637 (calculated), 1197.4667 (found). IR: υ = 2922 (m), 2852 (m), 1611 (s), 1575 (m), 1532 (m), 1504 (m), 1461 (s), 1447 (m), 1397 (m), 1383 (m), 1340 (w), 1301 (m), 1267 (m), 1245 (w), 1213 (w), 1171 (m), 1152 (m), 1131 (w), 1112 (w), 1035 (w), 1016 (w), 994 (w), 973 (w), 931 (w), 913 (w), 855 (w), 833 (w), 807 (w), 769 (w), 754 (s), 739 (m), 722 (w), 674 (m), 620 (w) cm-1. UV-vis (DMSO): λmax (ε) = 301 (3.41x104), 336 (2.07x104), 354 (2.43x104), 407 (5.22x104) nm (cm-1 mol-1 L). m.p. = 272–275 oC.  Synthesis of Bis(Zinc(II) Salphen) Complex 44c. Bis(zinc(II) salphen) complex 44c (89%, yellow solid) was prepared by the same procedure and purification as for bis(zinc(II) salphen) complex 44a.  Data for Bis(Zinc(II) Salphen) Complex 44c. 1H NMR (400 MHz, DMSO-d6) δ 8.98 (s, 4H, CH=N), 7.48 (s, 4H, aromatic CH), 7.43 (t, 4H, aromatic CH), 7.21 (t, 4H, aromatic CH), 6.70 (d, 4H, aromatic CH), 6.51 (t, 4H, aromatic CH), 4.12 (t, 4H, OCH2), 3.92 (s, 6H, OCH3), 1.80 (quintet, 4H, CH2), 1.49 (quintet, 4H, CH2), 1.42 (broad, 4H, CH2) ppm. 13  C NMR (100.6 MHz, DMSO-d6) δ 171.7 (CH=N), 160.6, 160.5, 149.1, 148.4, 138.8,  135.7, 133.7, 132.7, 132.6, 122.9, 119.6, 112.8, 112.7, 100.5, 99.7 (aromatic C), 68.7 (OCH2), 56.1 (OCH3), 28.8, 28.7, 25.6 (CH2) ppm. ESI-MS: 983.2 ((M+Na)+), 1925.4 ((2M+H)+),  1944.4  ((2M+Na)+),  2986.5  ((3M+H)+).  HR-ESI-MS  for  44c+H+ 241  (C50H47N4O8Zn2): 959.1977 (calculated), 959.1953 (found). IR: υ = 2929 (w), 2915 (w), 2897 (w), 1613 (s), 1529 (m), 1505 (m), 1464 (s), 1446 (m), 1441 (m), 1379 (m), 1348 (w), 1316 (m), 1263 (s), 1244 (m), 1222 (w), 1213 (w), 1173 (s), 1150 (s), 1128 (w), 1111 (s), 1031 (m), 961 (w), 932 (w), 913 (m), 898 (w), 852 (w), 832 (m), 806 (w), 751 (s), 736 (s), 681 (w), 670 (w), 621 (w) cm-1. UV-vis (DMSO): λmax (ε) = 301 (4.66x104), 337 (3.11x104), 355 (3.77x104), 406 (7.62x104) nm (cm-1 mol-1 L). m.p. = 278–281 oC.  Synthesis of Bis(Zinc(II) Salphen) Complex 44d. Bis(zinc(II) salphen) complex 44d (92%, yellow solid) was prepared by the same procedure and purification as for bis(zinc(II) salphen) complex 44a.  Data for Bis(Zinc(II) Salphen) Complex 44d. 1H NMR (400 MHz, DMSO-d6) δ 8.95 (s, 4H, CH=N), 7.48 (s, 2H, aromatic CH), 7.47 (s, 2H, aromatic CH), 7.41 (d, 4H, aromatic CH), 7.21 (t, 4H, aromatic CH), 6.69 (d, 4H, aromatic CH), 6.50 (t, 4H, aromatic CH), 4.10 (q, 8H, OCH2), 1.77 (m, 8H, CH2), 1.54–1.43 (m, 12H, CH2), 1.33 (broad, 4H, CH2), 1.19 (broad, 28H, CH2), 0.80 (t, 6H, CH3) ppm.  13  C NMR (100.6 MHz, DMSO-d6) δ  171.7 (CH=N), 160.6, 148.8, 135.8, 133.6, 132.8, 132.8, 122.9, 119.6, 112.7, 101.1 (aromatic C), 68.8 (OCH2), 31.3, 29.1, 29.0, 29.0, 28.9, 28.9, 28.8, 28.8, 28.7, 25.7, 25.6, 22.1 (CH2), 13.9 (CH3) ppm. ESI-MS: 1271.7 ((M+H)+), 1293.7 ((M+Na)+), 1309.5 ((M+K)+), 2542.2 ((2M+H)+), 2564.0 ((2M+Na)+), 3834.0 ((3M+Na)+). HR-ESI-MS for 44d+Na+ (C72H90N4NaO8Zn2): 1289.5239 (calculated), 1289.5214 (found). IR: υ = 3051 (w), 2919 (m), 2850 (m), 2360 (m), 2341 (m), 1614 (s), 1531 (m), 1503 (m), 1464 (s), 1440 (m), 1380 (m), 1346 (w), 1318 (m), 1304 (w), 1264 (m), 1244 (m), 1222 (w), 1212 (w), 1171 (m), 1151 (s), 1129 (w), 1112 (m), 1032 (w), 962 (w), 938 (w), 913 (w), 847 242  (w), 832 (w), 807 (w), 750 (s), 735 (s), 669 (w) cm-1. UV-vis (DMSO): λmax (ε) = 301 (4.69x104), 337 (2.94x104), 355 (3.52x104), 407 (7.53x104) nm (cm-1 mol-1 L). m.p. = 153–156 oC.  243  7.5 References  1.  (a) Ikkala, O.; Ras, R. H. A.; Houbenov, N.; Ruokolainen, J.; Pääkkö, M.; Laine, J.; Leskelä, M.; Berglund, L. A.; Lindström, T.; ten Brinke, G.; Iatrou, H.; Hadjichristidis, N.; Faul, C. F. J. Faraday Discuss. 2009, 143, 95. (b) Lee, C. C.; Grenier, C.; Meijer, E. W.; Schenning, A. P. H. J. Chem. Soc. Rev. 2009, 38, 671.  2.  (a) Schenning, A. P. H. J.; Meijer, E. W. Chem. Commun. 2005, 3245. (b) Schenning, A. P. H. J.; Jonkheijm, P.; Hoeben, F. J. M.; Van Herrikhuyzen, J.; Meskers, S. C. J.; Meijer, E. 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Orange block (0.40 x 0.25 x 0.20 mm), a = 9.395(5) Å, b = 17.839(5) Å, c = 20.303(5) Å, α = γ = 90.000(5)°, β = 95.383(5)º, V = 3388(2) Å3, space group P21/n (monoclinic), Z = 4, mol. wt. = 731.21, T = 173(2) K, 51720 observed (8061 unique) reflections, R1 = 0.0667, wR2 = 0.1539, GOF = 1.175. 247  CCDC-771868 contains the supplementary crystallographic data. These data can be obtained free of charge from the Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. 25. Inokuchi, F.; Shinkai, S. J. Chem. Soc., Perkin Trans. 2 1996, 601. 26. (a) Ishi-i, T.; Hirashima, R.; Tsutsumi, N.; Amemori, S.; Matsuki, S.; Teshima, Y.; Kuwahara, R.; Mataka, S. J. Org. Chem. 2010, 75, 6858. (b) Petitjean, A.; Cuccia, L. A.; Schmutz, M.; Lehn, J.-M. J. Org. Chem. 2008, 73, 2481. (c) Liang, Y.; Jasbi, S. Z.; Haftchenary, S.; Morin, S.; Wilson, D. J. Biophys. Chem. 2009, 144, 1. 27. (a) Kleij, A. W.; Kuil, M.; Lutz, M.; Tooke, D. M.; Spek, A. L.; Kamer, P. C. J.; van Leeuwen, P. W. N. M.; Reek, J. N. H. Inorg. Chim. Acta 2006, 359, 1807. (b) Singer, A. L.; Atwood, D. A. Inorg. Chim. Acta 1998, 277, 157. (c) Odoko, M.; Tsuchida, N.; Okabe, N. Acta Crystallogr., Sect. E 2006, 62, m708. 28. (a) Kleij, A. W. Dalton Trans. 2009, 4635. (b) Kuil, M.; Goudriaan, P. E.; Kleij, A. W.; Tooke, D. M.; Spek, A. L.; van Leeuwen, P. W. N. M.; Reek, J. N. H. Dalton Trans. 2007, 2311. (c) Castilla, A. M.; Curreli, S.; Carretero, N. M.; Escudero-Adán, E. C.; Benet-Buchholz, J.; Kleij, A. W. Eur. J. Inorg. Chem. 2009, 2467. (d) Kuil, M.; Goudriaan, P. E.; van Leeuwen, P. W. N. M.; Reek, J. N. H. Chem. Commun. 2006, 4679. (e) Escudero-Adán, E. C.; Benet-Buchholz, J.; Kleij, A. W. Inorg. Chem. 2008, 47, 4256. (f) Houjou, H.; Ito, M.; Araki, K. Inorg. Chem. 2009, 48, 10703. 29. Luboch, E.; Wagner-Wysiecka, E.; Biernat, J. F. J. Supramolecular Chemistry 2002, 2, 279. 30. Sheldrick, G. M. SHELXL-97, University of Göttingen, Germany, 1997. 248  CHAPTER 8 CONCLUSIONS AND FUTURE DIRECTIONS  8.1 Overview  Much research in the field of nanofibers has focused on the incorporation of metal centers into the one-dimensional superstructures because metal-containing nanofibers have proven to be fascinating materials with intriguing structures, dynamic properties, and excellent potential for applications. 1 Numerous methods have been used to generate nanofibers, however, construction through coordination chemistry and electrostatic interactions is still in its infancy and has not been widely explored. Self-assembly through electrostatic and metal-ligand interactions provides a robust strategy to build diverse one-dimensional fibrous structures with various degrees of control.  The work presented in this thesis aims to develop and generate metal-containing fibrous structures by utilizing Schiff-base macrocycles and metal salphen complexes organized through electrostatic interaction and coordination chemistry approaches. To understand the self-assembled supramolecular structures prepared, a series of morphological studies was performed by imaging with optical and electron microscopes.  Chapter 3 demonstrated that [3+3] Schiff-base macrocycles 42a and 42b, containing a crown-ether like central pore, mixed with alkali metal and ammonium salts self-assemble into nanofibers with up to four levels of hierarchy. Moreover, the 249  dimensions of the fibrous structures could be affected by the rate of evaporation of the sample solutions. This ion-induced electrostatic self-assembly to construct nanofibers with multi-level hierarchy can serve as a model to understand organizations that employ similar approaches in biological system and to design functional biomimetic materials. Surprisingly, lyotropic liquid crystallinity was observed in various organic solvents when the alkali metal and ammonium salts were introduced to the macrocycles equipped with long alkoxy substituents (macrocycles 42c–e) as illustrated in Chapter 4. Lyotropic liquid crystals in organic solvents through electrostatic assembly can potentially be useful for preparing organized supramolecular materials as anisotropic ion-conductors or templates for nanostructures.  In Chapters 5–7, a series of metallosalphen complexes was synthesized and electron micrographs revealed superstructures with various morphologies that depend on the transition metals being incorporated. Interestingly, zinc(II) salphen complexes (both mono- and dinuclear complexes, 43 and 44, respectively) showed a remarkable helical nanofibrillar morphology, whereas the other metal complexes only displayed micron-sized clusters. Furthermore, the helicity in the nanofibers were enhanced by modifying the peripheral substituents of the zinc(II) salphen complexes with carbohydrates (glucosyl and galactosyl groups, complexes 43f and 43g). In addition, the surface texture and diameter of the fibers can be altered by external stimuli, such as addition of ditopic proligand, and hydrophobic effects. Self-assembly of zinc(II) salphen complexes into bundles of nanofibers through coordination chemistry and the modification of their morphologies with external stimuli may be helpful to provide  250  insight in directing the supramolecular organization for nano-sized wires and biological materials.  Chapter 2 showed that Schiff-base chemistry could be used to form large, conjugated [6+6] macrocycles 40 and 41 from the condensation of six diaminoaryl and six dialdehyde-functionalized aromatic rings. These new macrocycles are promising for the complexation of transition metals, possibly even clusters, on their interiors. This work is an important step in the development of large macrocycles under thermodynamic control, and it illustrates the powerful paradigm of self-assembly. Metal complexes of these macrocycles may prove useful for developing new imaging agents 2 and magnetic clusters. 3  Overall, the goals of this thesis were achieved. A firm understanding of the supramolecular self-assembly of shape-persistent macrocycles and zinc(II) salphen complexes into nanofibers through electrostatic and metal-ligand interactions has been developed. The work in this thesis lays the groundwork for future investigations in this field for designing and constructing fiber superstructures.  251  8.2 Future Directions  The work presented in this thesis is part of an effort to develop metal-containing nanofibers, both linear and helical, from Schiff-base complexes using coordination chemistry and electrostatic interactions. A benefit of this supramolecular approach is the ability to control the size and properties of the fibrous structures by modifying the functionality of the organic Schiff-base components (e.g., the peripheral substituents and shape of the ligands). In addition, changes in the oxidation state and electronic configuration of the metal centers in the coordination polymers may alter the morphology and properties of the fibrous aggregates.  In the context of expanding fibrous nanostructures from electrostatic self-assembly of Schiff-base macrocycles, the diameters of one-dimensional aggregates can possibly be enhanced by incorporating bigger macrocyclic building blocks, and [6+6] Schiff-base macrocycle 40 would be a good candidate. However, solubility has been a challenge for macrocycle 40 and this is the first obstacle that needs to be overcome. It is postulated that the poor solubility is associated to the aggregation of the macrocycles in solution. Rather than having longer substituents on the phenylenediamine units to promote solubility, a derivative of 4,6-diformylresorcinol (45) with a phenyl ring on each carbonyl group was synthesized (i.e., compound 69). It was proposed that the phenyl rings would orient perpendicular to the macrocycle, which is supported by computation modelling, to prevent the macrocyclic units from stacking together, leading to an increase the solubility. Similar to the synthetic route for macrocycle 40 mentioned in Chapter 2, compound 69  252  was first reacted with 4,5-dihexyloxyphenylenediamine (46a) to give a new intermediate compound 70 (Scheme 8.1). It could then undergo Schiff-base condensation with compound 45 to obtain a new macrocycle with improved solubility. 4 Based on our previous studies of [6+6] Schiff-base macrocycles 40 and 41, the condensation between compounds 45 and 70 was anticipated to lead to a hexagon-shaped macrocycle. Surprisingly, however, 4,6-diformylresorcinol and compound 70 reacted to give exclusively a [2+2] Schiff-base macrocycle (71, Scheme 8.1). MALDI-TOF mass spectrometry clearly indicated the [2+2] macrocycle was selectively formed, with no evidence of the anticipated hexagon-shaped macrocycle. Macrocycle 71 appears highly strained and must adopt a non-planar geometry, which is illustrated by computational modelling (Figure 8.1). It is hypothesized that the additional phenyl rings on compound 70 forced the imine groups and phenylenediamine components to be out of plane, which made the geometry of compound 70 no longer fit to assemble into a hexagonal macrocycle. Similar [2+2] Schiff-base macrocycle (72, Figure 8.2) was obtained when compound  70  reacted  with  2,7-diformyl-3,6-dihydroxynaphthalene 49.  Further  investigation is required to solve the solubility problem, possibly by modifying the peripheral substituents, in order to undertake experiments for fiber construction.  253  H13C6O  OC6H13  H13C6O  OC6H13  H13C6O  OC6H13  + 2 O  O  HO  OH  69  N H2N  NH2  H2N  HO  46a  + 2H2O  N NH2  OH  70 O  O  HO  OH  45 H13C6O  OC6H13  H13C6O  OC6H13  N  N  N  OH HO  OH HO  N  + 4H2O N  OH HO  OH HO  N  N  H13C6O  N  OC6H13  H13C6O  OC6H13  71  Scheme 8.1. Syntheses of compound 70 and [2+2] Schiff-base macrocycle 71.  Figure 8.1. Calculated structure of [2+2] Schiff-base macrocycle 71. Please note that the hexyloxy chains were removed for clarity. 254  H13C6O  OC6H13  H13C6O  OC6H13  N  N  N  N  OH HO  OH HO  OH HO  OH HO  N  N  H13C6O  N  N  OC6H13  H13C6O  OC6H13  72  Figure 8.2. Chemical structure of [2+2] Schiff-base macrocycle 72.  Recent investigations in the field demonstrate the potential of using the metal-ligand interactions to produce fibrillar materials. Coordination polymers can be self-assembled from monomeric ditopic ligands with suitable metals. Here, metal salphen complexes 73 and 74 having two imidazolyl units on the salicylaldehyde moieties were proposed as shown in Scheme 8.2. There are reports on compounds with imidazolyl groups coordinating to copper and silver salts to form intriguing metal complexes. 5 Therefore, the incorporation of copper and silver to complexes 73 and 74 may lead to the formation of helical coordination polymers. Scheme 8.2 illustrated the proposed route reaching the target salphen complexes, which involves the preparation of salicylaldehydes 77 and 78 first from bromosalicylaldehydes 75 and 76 with imidazole. The use of facile Schiff-base chemistry on salicylaldehydes 77 and 78 with phenylenediamine 46 in the presence of transition metal salts would yield metal salphen complexes 73 and 74. The metallosalphen complexes could then be reacted with copper and silver salts to obtain the 255  potential helical coordination polymers. If salphen complexes 73 and 74 can self-assemble into the target polymers, the resulting supramolecular structures would have alternating metal centers along the backbones. This may lead to interesting electronic properties with different combinations of transition metal within the salphen unit and the bridging metal. The formation of supramolecular structure and network would be studied and confirmed through imaging by various electron microscopies.  R  R R  O OH  H N  O  N  OH  H2N  N  Br  R  NH2  46  N  M(OAc)2  O  N M O  N  75  N  77  N R  N  73  N  R R  H N O  O  N  OH  OH N  NH2  46  N  N  N M  M(OAc)2  Br  76  H2N  R  O  O  N  78  N  N  74  N  Cu or Ag salts 73 or 74  helical coordination polymers  Scheme 8.2. Proposed synthetic route to metallated salphen complexes 73 and 74.  Another interesting area of exploration is the use of coordination chemistry and electrostatic interactions to develop new materials with hierarchical supramolecular structures. While significant advances using hydrogen-bonding and π-stacking have 256  advanced this field, coordination chemistry and electrostatic assembly have been rarely applied. Given the large number and diversity of coordination structures available, it should be possible to construct very interesting, functional hierarchically-structured nanofibers. Without a doubt, one can expect many new exciting developments to emerge in the field of fibrillar coordination chemistry in the coming decade.  In spite of the significant advances that have been seen, there are still many areas to explore. For instance, nanofibers with hollow interiors would be an exciting area, which is also a topic we are interested to explore with our Schiff-base macrocycles. The development of hollow nanofibers based on coordination chemistry may be useful to generate catalytic materials and for host-guest chemistry. Although not in the coordination chemistry and electrostatic interaction categories of this thesis, two possible routes are outlined in Scheme 8.3 to prepare [3+3] Schiff-base macrocycle 79 that has the potential to generate hollow nanofibers. This formation of fibrous structure involves taking advantage of the intermolecular hydrogen-bonding and π-stacking abilities of the peripheral carbohydrate substituents and the perimeter of the conjugated macrocycle, respectively. Shinkai and co-workers have reported this bottom-up approach to form self-assembled fibrous superstructures from their carbohydrate-appended porphyrins. 6 One foreseeable problem with this approach is the formation of random hydrogen-bonded aggregates rather than one-dimensional fibers. This random aggregation can possibly be minimized by having very diluted sample solutions when performing morphological analyses.  257  RO  RO O  O HO  N  OR  N  OH HO  +  OH  OR  H2N  OH  NH2  HO  N  N HO  RO  OH  N  N  OR  RO  80  OR  81  46 OAc O  46g, 81a R = AcO AcO  AcO  deacetylation  AcOOAc O  46h, 81b R = AcO  AcO  RO  RO O  O HO  OH  OR  N  OR  N  OH HO  + H2N  OH  NH2  HO  N  N HO  RO  OH  N  N  RO  80  OR OR  79  46 OH O  46i, 79a R = HO HO  HO  HOOH O  46j, 79b R = HO  HO  Scheme 8.3. Proposed synthetic route to [3+3] Schiff-base macrocycle 79.  258  8.3 References  1.  (a) Tu, T.; Assenmacher, W.; Peterlik, H.; Weisbarth, R.; Nieger, M.; Dötz, K. H. Angew. Chem. Int. Ed. 2007, 46, 6368. (b) Gansäuer, A.; Winkler, I.; Klawonn, T.; Nolte, R. J. M.; Feiters, M. C.; Börner, H. G.; Hentschel, J.; Dötz, K. H. Organometallics 2009, 28, 1377. (c) Wang, Z.; Medforth, C. J.; Shelnutt, J. A. J. Am. Chem. Soc. 2004, 126, 16720. (d) Jung, J. S.; Lee, J. W.; Kim, K.; Cho, M. Y.; Jo, S. G.; Joo, J. Chem. Mater. 2010, 22, 2219.  2.  (a) Henig, J.; Tóth, E.; Engelmann, J.; Gottschalk, S.; Mayer, H. A. Inorg. Chem. 2010, 49, 6124. (b) Huang, C.-H.; Morrow, J. R. Inorg. Chem. 2009, 48, 7237.  3.  (a) Paraschiv, C.; Andruh, M.; Journaux, Y.; Žak, Z.; Kyritsakas, N.; Ricard, L. J. Mater. Chem. 2006, 16, 2660. (b) Bartoli, S.; Bazzicalupi, C.; Biagini, S.; Borsari, L.; Bencini, A.; Faggi, E.; Giorgi, C.; Sangregorio, C.; Valtancoli, B. Dalton Trans. 2009, 1223.  4.  Frischmann, P. D.; Jiang, J.; Hui, J. K.-H.; Grzybowski, J. J.; MacLachlan, M. J. Org. Lett. 2008, 10, 1255.  5.  (a) Zhang, S.; Yang, S.; Lan, J.; Yang, S.; You, J. Chem. Commun. 2008, 6170. (b) Dobrzańska, L.; Lloyd, G. O.; Raubenheimer, H. G.; Barbour, L. J. J. Am. Chem. Soc. 2006, 128, 698. (c) Dobrzańska, L.; Lloyd, G. O.; Raubenheimer, H. G.; Barbour, L. J. J. Am. Chem. Soc. 2005, 127, 13134.  6.  Kawano, S.-i.; Tamaru, S.-i.; Fujita, N.; Shinkai, S. Chem. Eur. J. 2004, 10, 343.  259  

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