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Structure-property relationships in cyclopentadienyliron containing compounds Vakili, Sarrah A. C. 2008

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STRUCTURE-PROPERTY RELATIONSHIPS IN CYCLOPENTADIENYLIRON CONTAINING COMPOUNDS  by  Sarrah A. C. Vakili  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF  DOCTOR OF PHILOSOPHY in The College of Graduate Studies (Chemistry)  THE UNIVERSITY OF BRITISH COLUMBIA (OKANAGAN)  November 2008 © Sarrah A. C. Vakili, 2008  Abstract Within this thesis, several classes of compounds containing cyclopentadienyliron complexes were prepared. These compounds were of the following four classes: linear polymers – containing ester, ether and thioether linkages with varying ratios of aliphatic to aromatic spacers within the backbone of the polymer; star-shaped molecules – discrete molecules containing either one or two branch points as well as ether and ester linkages within the backbone of the molecule; hyperbranched polymers – highly branched one-pot synthesis polymers with ether linkages for the polymeric backbone; and water soluble complexes and chelates – discrete molecules containing the amino acid cysteine used to induce water solubility in otherwise water insoluble compounds as well as their subsequent complexation/chelation to various transition and main group metals. For each of these classes, the thermal and spectroscopic properties were probed. In addition, the linear polymers were demetallated to examine the influence of the metal on the aforementioned compounds as well as the molecular weights. Various viscometric parameters were examined for the star-shaped, linear and hyperbranched polymers. The degree of branching and molecular weights of the hyperbranched polymers were determined. For the novel water soluble complexes and chelates, biological testing along with increased spectroscopic data was collected and will be presented. Keywords: cyclopentadienyliron, thermal anaylsis, spectroscopic anaysis, viscometry, transition metals, iron, polymer, star-shaped molecules, hyperbranched polymers, metal coordination  ii  Table of Contents Section  Page  Abstract __________________________________________________________ ii Table of Contents __________________________________________________ iii List of Tables ______________________________________________________ viii List of Figures _____________________________________________________ xii Abbreviations _____________________________________________________ xvi Acknowledgments __________________________________________________ xix 1  Introduction 1.1  _______________________________________________ 1  Polymer topologies  ___________________________________ 2  1.1.1 Linear polymers prepared by condensation polymerization  2  1.1.2 Star-shaped molecules, polymers and dendrimers _________ 8 1.1.3 Hyperbranched polymers ____________________________ 12 1.2  Water-soluble polymers _________________________________ 15  1.3  Incorporation of metals into polymers ______________________ 16 1.3.1 Metal coordination _________________________________ 17 1.3.2 Cyclopentadienyliron complexes ______________________ 17  1.4  Instrumental methods not commonly studied during undergraduate _________________________________________ 24 1.4.1 Polarized optical microscopy (POM) __________________ 24 1.4.2 Viscometry ______________________________________ 24  2  Linear polymers containing cyclopentadienyliron moieties as well as ether, ester and thioether linkages ________________________________ 32  iii  2.1  Introduction ___________________________________________ 32  2.2  Results and discussion ___________________________________ 33 2.2.1 Synthesis and properties of cyclopentadienyliron containing monomers ____________________________________ 33 2.2.2 Synthesis and properties of cyclopentadienyliron containing polymers with an aliphatic spacer _________________ 43 2.2.3 Synthesis and properties of cyclopentadienyliron containing polymers with an aromatic spacer _________________ 49 2.2.4 Synthesis and properties of demetallated polymers with an aliphatic spacer _____________________________________ 55 2.2.5 Synthesis and properties of demetallated polymers with an aromatic spacer ______________________________________ 60  2.3  Conclusions ___________________________________________ 65  2.4  Experimental __________________________________________ 66 2.4.1 Characterization ___________________________________ 66 2.4.2 Materials ________________________________________ 67 2.4.3 Procedures _______________________________________ 67 2.4.3.1 Synthesis of 2.3 ___________________________ 67 2.4.3.2 Synthesis of 2.5a-h _________________________ 68 2.4.3.3 Synthesis of 2.7a, c-e, g, h, 2.9a-h _____________ 68 2.4.3.4 Synthesis of 2.10a, c-e, g, h, 2.11a-h ___________ 68  3  Linear and singly branched star-shaped molecules containing cyclopentadienyliron moieties _________________________ 70  iv  3.1  Introduction __________________________________________ 70  3.2  Results and discussion __________________________________ 71 3.2.1 Synthesis and properties of allyl-capped star-shaped molecules _____________________________________________ 71 3.2.2 Synthesis and properties of ester-containing star-shaped molecules ____________________________________________ 83 3.2.3 Synthesis and properties of ester-containing singly branched star-shaped molecules (1st generation dendrimers) ____ 89 3.2.4 Other star-shaped molecules attempted and tested ________ 97 3.2.5 Viscometric studies of cyclopentadienyliron compounds ___ 99  3.3  Conclusions ___________________________________________ 116  3.4  Experimental __________________________________________ 117 3.4.1 Materials ________________________________________ 117 3.4.2 Characterization __________________________________ 117 3.4.3 Procedures _______________________________________ 118 3.4.3.1 Synthesis of 3.2, 3.5, 3.7, 3.9 _________________ 118 3.4.3.2 Synthesis of 3.4, 3.6, 3.8 _____________________ 118 3.4.3.3 Synthesis of 3.12-3.16 ______________________ 118 3.4.3.4 Synthesis of 3.17, 3.18 ______________________ 119 3.4.3.5 Synthesis of 3.20, 3.21, 3.24 _________________ 119 3.4.3.6 Synthesis of 3.23a,b ________________________ 120  4 Hyperbranched polymers containing cyclopentadienyliron _______________ 4.1  121  Introduction ___________________________________________ 121  v  4.2  Results and discussion ___________________________________ 122 4.2.1 Synthesis and properties of hyperbranched polymers based upon phloroglucinol _______________________________ 122 4.2.2 Synthesis and properties of hyperbranched polymers based upon chlorostar ___________________________________ 129 4.2.3 Synthesis and properties of hyperbranched polymers based upon alcohol star _________________________________ 136  4.3  Conclusions __________________________________________ 140  4.4  Experimental _________________________________________ 141 4.4.1 Characterization __________________________________ 141 4.4.2 Materials ________________________________________ 142 4.4.3 Procedures _______________________________________ 142 4.4.3.1 Synthesis of 4.1a, 4.2a, 4.6a, 4.11a _____________ 142 4.4.3.2 Synthesis of 4.1b, 4.2b, 4.6b, 4.7-4.9, 4.11b ______142 4.4.3.3 Synthesis of gelation product 4.6c ______________ 143 4.4.3.4 Synthesis of 4.3, 4.4, 4.10, 4.12 ________________143  5  Conclusions _________________________________________________ 144  6  Future work _________________________________________________ 146 6.1 Water soluble complexes _____________________________ 146 6.1.1 Introduction ________________________________ 146 6.1.2  Results and discussion _______________________ 149 6.1.2.1 Synthesis and properties of cyclopentadienyliron amino acids ______________ 149  vi  6.1.2.2 Synthesis and properties of metal chelates of cyclopentadienyliron amino acids ____________ 161 6.1.3  Experimental ____________________________________ 171 6.1.3.1 Characterization ___________________________ 171 6.1.3.2 Materials ________________________________ 171 6.1.3.3 Procedures ________________________________ 172 6.1.3.3.1 Synthesis of 6.2a-c _________________ 172 6.1.3.3.2 Synthesis of 6.2d ___________________ 172 6.1.3.3.3 Synthesis of 6.4-6.6 _________________ 172  6.1.4 Conclusions _______________________________________ 173 7  References __________________________________________________ 174  vii  List of Tables Table  Page  2.1  NMR shifts for compound 2.3 in acetone-d6 _______________________ 36  2.2  1  2.3a  13  38  2.3b  13  39  2.4  Thermal analysis of 2.5d, e, g, h ________________________________ 41  2.5  1  2.6  13  2.7  Solubility data for 2.7a, c-e, g, h ________________________________ 47  2.8  Thermal analyses of 2.7a, c-e, g, h _______________________________ 48  2.9  Viscosity and molecular weight of 2.7c, e _________________________ 49  2.10  1  2.11  13  2.12  Solubility data for polymers 2.9a-h ______________________________ 53  2.13  Thermal analysis of 2.9a-h _____________________________________ 54  2.14  Viscosity and molecular weight of 2.9c, e _________________________ 55  2.15  1  2.16  Solubility data for 2.10a, c-e, g, h _______________________________ 58  2.17  Thermal analysis for 2.10a, c-e, g, h ______________________________ 59  2.18  Molecular weights of 2.10a, c-e, g, h in THF _______________________ 60  2.19  1  2.20  Solubility data for 2.11a-h ______________________________________ 63  H NMR values, IR and yields for monomers 2.5a-h _________________ 37 C NMR values for 2.5a-h in acetone-d6 ________________________ C NMR values for 2.5a-h in DMSO-d6 ________________________  H NMR values, IR and yields for 2.7a, c-e, g, h in DMSO-d6 _________ 45 C NMR shifts for 2.7a, c-e, g, h in DMSO-d6 ____________________ 46  H NMR values, IR and yields for 2.9a-h in DMSO-d6 _______________ 51 C NMR shifts for 2.9a-h in DMSO-d6 __________________________ 52  H NMR shifts and yields for 2.10a, c-e, g, h ______________________ 57  H NMR shifts, IR and yields for 2.11a-h in DMSO-d6 _______________ 62  viii  2.21  Thermal analysis for 2.11a-h ___________________________________ 63  2.22  Molecular weights of 2.11a-h in THF ____________________________ 65  3.1  1  3.2  13  3.3  1  3.4  13  3.5  Percent yields and elemental analysis of 3.13-3.16 __________________ 81  3.6  Thermal analysis and viscosity data for 3.12-3.16 ___________________ 82  3.7  1  3.8  13  3.9  Percent yields and elemental analysis of 3.20, 3.21 __________________ 88  3.10  Thermal analysis of 3.20, 3.21 __________________________________ 89  3.11  Percent yields and elemental analysis of 3.24 ______________________ 91  3.12  1  3.13  13  3.14  1  3.15  13  3.16  Thermal analysis of 3.24 _______________________________________ 97  3.17  Glass transitions of 3.10, 3.12, 3.25 and viscosity of 3.10, 3.11, 3.25a,c,d 98  3.18  Intrinsic viscosities and constants determined by graphing of the  H NMR and yields for 3.2, 3.4-3.9 _____________________________ C NMR values for 3.2, 3.4-3.9 _______________________________  74 76  H NMR values for 3.12-3.16 __________________________________ 79 C NMR values for 3.12-3.16 _________________________________  80  H NMR values of 3.20 and 3.21 in DMSO-d6 _____________________ 86 C NMR values for 3.20 and 3.21 in DMSO-d6 ___________________  88  H NMR values and yields of 3.23a, b ____________________________ 92 C NMR values of 3.23a, b ____________________________________ 93  H NMR values of 3.24 in DMSO-d6 _____________________________ 94 C NMR of 3.24 in DMSO-d6 _________________________________ 96  viscometric data _____________________________________________ 101 3.19  Intrinsic viscosity and molecular weights as used for the Mark-Houwink plots __________________________________________ 103  ix  3.20  Intrinsic viscosity values and related constants for the linear polymers  106  3.21  Intrinsic viscosity values for the linear polymers ___________________ 107  3.22  Viscometric radii, hydrodynamic radii and molecular compactness for the star-shaped molecules and linear polymers __________________ 108  3.23  Shrinking factors for linear polymers of similar molecular weight to star-shaped molecules _________________________________________ 111  3.24  Molecular weight estimation using the calibration curve for the linear polymers as compared to GPC data ______________________________ 114  3.25  Intrinsic viscosity values and constants as calculated for the Huggins, Kramer and Fuoss equations ___________________________________ 115  3.26  Molecular weights of the hyperbranched polymers __________________ 116  4.1  1  4.2  13  4.3  Thermal analysis for 4.1b, 4.2b, 4.3, 4.4 __________________________ 127  4.4  Inherent viscosity and molecular weights of 4.1b, 4.2b, 4.3, 4.4 ________ 128  4.5  1  4.6  13  4.7  Thermal analysis for 4.6b,c, 4.7-4.10 _____________________________ 134  4.8  Inherent viscosity and molecular weights of 4.6b, 4.7-4.10 ___________ 135  4.9  1  4.10  13  4.11  Thermal analysis for 4.11b, 4.12 ________________________________ 140  4.12  Inherent viscosity and molecular weights for 4.11b, 4.12 _____________ 140  H NMR values and yields for 4.1-4.4 in DMSO-d6 __________________ 124 C NMR values for 4.1-4.4 in DMSO-d6 __________________________ 126  H NMR and yields for 4.6-4.10 in DMSO-d6 _____________________  131  C NMR values for 4.6-4.10 in DMSO-d6 _________________________ 133  H NMR values and yields for 4.11, 4.12 in DMSO-d6 ______________ C NMR for 4.11, 4.12 in DMSO-d6 ___________________________  137 139  x  6.1  1  6.2  13  6.3  Vis data for 6.2 in nm ________________________________________ 157  6.4  IR data for 6.2 in cm-1 ________________________________________ 158  6.5  Thermal analysis of 6.2 ________________________________________ 159  6.6  Biological testing of 6.2 _______________________________________ 160  6.7  1  6.8  13  6.9  Vis data for 6.4-6.6 in nm _____________________________________ 167  6.10  IR data for 6.4-6.6 in cm-1 ______________________________________ 168  6.11  Thermal analysis for 6.4-6.6 ____________________________________ 169  6.12  Biological testing for 6.4-6.6 ___________________________________ 170  H NMR values and yields for 6.2 _______________________________ 152 C NMR values for 6.2 _______________________________________ 154  H NMR values and yields of 6.4-6.6 in D2O _______________________ 163 C NMR values for 6.5a ______________________________________ 165  xi  List of Figures Figure  Page  1.1  Polyesters formed by condensation polymerization _________________ 3  1.2  Schematic examples of (A) dendrimer; (B) star-shaped molecule; (C) star-shaped polymer _______________________________________ 9  1.3  Methods of dendrimer growth __________________________________ 10  1.4  A schematic of dendrimer generations ___________________________ 11  1.5  Schematic showing dendritic, linear and terminal units in a hyperbranched polymer _______________________________________ 13  1.6  Orbital diagram for octahedral complexes where (a) is the stable form of iron in ferrocene and (b) is unstable ___________________________ 19  2.1  1  2.2  13  2.3  1  2.4  13  2.5  13  2.6  DSC thermogram of 2.5d ______________________________________ 41  2.7  Optical microscopy micrographs of the thin film sections of 2.5d and  H NMR spectrum of compound 2.3 in acetone-d6 __________________ 35 C APT NMR of compound 2.3 in acetone-d6 _____________________ 36  H NMR spectrum of 2.5d in acetone-d6 __________________________ 38 C APT NMR of 2.5d in acetone-d6 _____________________________ 40 C APT NMR of 2.5d in DMSO-d6 ____________________________  40  2.5g depending on the temperature ______________________________ 42 2.8  1  2.9  13  2.10  TGA thermogram of 2.7d ______________________________________ 48  2.11  1  H NMR spectrum of 2.7e in DMSO-d6 __________________________ 44 C APT NMR of 2.7e in DMSO-d6 _____________________________ 47  H NMR spectrum of 2.9f in DMSO-d6 __________________________  50  xii  2.12  13  2.13  DSC thermogram of 2.9b ______________________________________ 54  2.14  TGA thermogram of 2.9d ______________________________________ 55  2.15  1  2.16  TGA thermogram of 2.10d _____________________________________ 58  2.17  DSC thermogram of 2.10a _____________________________________ 59  2.18  1  2.19  TGA thermogram of 2.11d _____________________________________ 64  2.20  DSC thermogram of 2.11b _____________________________________ 64  3.1  1  3.2  13  3.3  1  3.4  13  3.5  Viscosity of 3.13 as determined in DMSO at 25 oC at 100 RPM _______ 83  3.6  1  3.7  13  3.8  1  3.9  13  3.10  1  3.11  13  3.12  Structure of 3.25a-d __________________________________________ 99  3.13  Classic Kramer and Huggins plots outside of the polyelectrolyte region  C NMR of 2.9f in DMSO-d6 _________________________________  53  H NMR spectrum for 2.10c in chloroform-d ______________________ 57  H NMR spectrum for 2.11g in DMSO-d6 ________________________  62  H NMR spectrum of 3.2 in acetone-d6 ___________________________ 73 C APT NMR of 3.2 in acetone-d6 _____________________________  75  H NMR spectrum of 3.13 in DMSO-d6 __________________________ 78 C APT NMR of 3.13 in DMSO-d6 ____________________________  80  H NMR spectrum of 3.20a in DMSO-d6 _________________________ 85 C APT NMR of 3.20a in DMSO-d6 ____________________________ 87  H NMR spectrum of 3.23b in DMSO-d6 _________________________ 92 C APT NMR of 3.23b in DMSO-d6 ___________________________  93  H NMR spectrum of 3.24b in DMSO-d6 _________________________ 95 C APT NMR of 3.24b in DMSO-d6 ____________________________ 96  for star 3.11 _________________________________________________ 100  xiii  3.14  Fuoss plot for star 3.11 _______________________________________  3.15  Mark-Houwink plots for the star-shaped molecules, including the  101  equation of the lines ___________________________________________ 103 3.16  Mark-Houwink plots for the star-shaped molecules with cyclopentadienyliron complexes at the periphery (3.10, 3.25a,c,d) _______________ 104  3.17  Mark-Houwink plots for the star-shaped molecules with an organic group at the periphery (3.11, 3.13-3.16) ___________________________ 105  3.18  Mark-Houwink plots for the linear polymers based upon the approximate weights calculated from the organic anologues estimated by GPC __________________________________________  3.19  107  Graph of the molecular weight of the star-shaped molecules versus the calculated viscometric radii _____________________________________ 109  3.20  Graph of the molecular weight of the star-shaped molecules versus the calculated hydrodynamic radii __________________________________ 110  3.21  Graph of the inherent viscosity of star-shaped molecules versus the molecular weight ____________________________________________ 112  3.22  Calibration graph with the equation of the line prepared from the inherent viscosity at 0.5 g/dL versus the molecular weight ___________________ 113  4.1  1  4.2  13  4.3  1  4.4  13  4.5  TGA thermogram of 3.12, 4.6c, 4.10, 4.6b ________________________ 135  H NMR spectrum of 4.1b in DMSO-d6 __________________________ 124 C APT NMR of 4.3 in DMSO-d6 _____________________________  125  H NMR spectrum of 4.6b in DMSO-d6 __________________________ 132 C APT NMR of 4.6b in DMSO-d6 _____________________________ 133  xiv  4.6  1  4.7  13  C APT NMR of 4.11b in DMSO-d6 ___________________________  139  6.1  1  H NMR spectrum of 6.2b in D2O ______________________________  152  6.2  COSY NMR of 6.3b in D2O ___________________________________ 153  6.3  13  6.4  HSQC of 6.2b in D2O _________________________________________ 155  6.5  HMBC of 6.2b in D2O ________________________________________ 156  6.6  Vis spectrum of 6.2b _________________________________________ 157  6.7  IR spectra of 6.2 _____________________________________________ 158  6.8  TGA thermogram of 6.2b ______________________________________ 160  6.9  1  6.10  COSY NMR of 6.5a in D2O ___________________________________ 164  6.11  13  6.12  HSQC of 6.5a in D2O _________________________________________ 166  6.13  Vis spectra of 6.5d ___________________________________________ 167  6.14  Vis spectra of 6.4b ___________________________________________ 167  6.15  IR spectra of 6.4b, 6.5d, 6.6a ___________________________________ 168  6.16  DSC thermogram for 6.3a, 6.4b,c ________________________________ 169  6.17  TGA thermogram for 6.5a ______________________________________ 170  H NMR spectrum of 4.11b in DMSO-d6 _________________________ 138  C APT NMR of 6.2c in DMSO _______________________________  154  H NMR spectrum of 6.5a in D2O _______________________________ 163  C DEPT135 NMR of 6.5a in D2O ______________________________ 165  xv  Abbreviations α  alpha, Mark-Houwink constant  APT  attached proton test  B  Fuoss constant  c  concentration  COSY  correlation spectroscopy  Cp  cyclopentadienyl  cP  centipoises (gcm-1s-1)  DB  degree of branching  DCC  dicyclohexylcarbodiimide  DCM  dichloromethane  DCU  dicyclohexylurea  DEPT  distortionless enhancement by polarization transfer  DMAP  4-dimethylaminopyridine  DMF  dimethylformamide  DMSO  dimethylsulphoxide  DP  degree of polymerization  DSC  differential scanning calorimetry  D2O  deuterated water  [η]  intrinsic viscosity  ηinh  inherent viscosity  ηr  relative viscosity  ηred  reduced viscosity  xvi  ηsp  specific viscosity  EtOH  ethanol  g  geometric shrinking factor  h  hydrodynamic shrinking factor  HMBC  heteronuclear multiple bond correlation  HPLC  high performance liquid chromatography  HSQC  heteronuclear single quantum correlation  k  constant, Mark-Houwink  kH  Huggins constant  kK  Kramer constant  IR  infrared  MeOH  methanol  MHz  mega hertz  Mn  number average molecular weight  MRI  magnetic resonance imaging  MW  molecular weight  Mw  weight average molecular weight  n  number of repeat units  NA  Avagadro’s number  NMR  nuclear magnetic resonance  PEEK  poly(ether ether ketone)  PET  poly(ethylene terephthalate)  PDI  polydispersity index  xvii  POM  polarized optical microscopy  RPM  rotations per minute  Rη  viscometric radius  RH  hydrodynamic radius  ρ  molecular compactness  Tendset  endset temperature  Tg  glass transition temperature  TGA  thermogravimetric analysis  THF  tetrahydrofuran  Tonset  onset temperature  vis  visible  xviii  Acknowledgments There are many people and places that I would like to thank for their support though out the duration of my thesis research and writing. These people and places include: - my husband Ramin, my son Amanj, my parents, Larry and Margery Carruthers, and my in-laws Esmaeil, Sharafat, Hana, Yosra, Fardin and Hassina Vakili; - my graduate supervisor Alaa S. Abd-El-Aziz; - my lab mates, including but not limited to Dr. Ahmed El-Bedair, Dr. Ahmed ElAgrody, Dr. Erin Todd, Basil Elmayergi, Leslie May, Jennilee Gavina, Chris Corkery and Diana Winram; - my committee members at The University of British Columbia Okanagan, Drs. McNeil and Smith; - my previous committee members at the University of Manitoba, Drs. Hegmann, Freund, and at The University of Winnipeg, Dr. Civetta; - my research collaborators and sounding boards, Drs. Goltz, Kroeker, Hegmann, Donald, Ata, Jayaraman, Mr. Jordan Betteridge and The University of Winnipeg, Department of Biology; - for technical expertise, support and repair, Drs. Marat, Shipley, Mr. Reinfelds, Mr. Balagus; - for research space and instrumentation, The Universities of Winnipeg, British Columbia Okanagan and Manitoba.  xix  1 Introduction Linear polymers are the oldest and most well known class of synthetic polymer. Initial work by Wallace H. Carothers illustrated the versatility, diversity and ease of synthesis of these new ‘rubbers’ during the 1920s and 1930s. His work introduced the world to the process and concept of polymerization in the form of polyesters and polyamides. He succinctly summarized polymerization in three main classes still used today, namely, condensation, addition and ring opening polymerizations.1 For this, he has been referred to as the father of synthetic polymer science.2 Sadly, he committed suicide, convinced that his life’s work was a failure.3 Great gains have been made in the field of polymer chemistry in the last eighty years. Several Nobel Prizes in Chemistry have been distributed to polymer chemists.4 These include a peer of Carothers, L. Ruzicka in 1939 for work on polymethylenes, as well as the development of polymerization catalysts for high molecular weight polymers by K. Ziegler and G. Natta in 1963 and by Y. Chauvin, R. H. Grubbs and R. R. Schrock in 2005. A Nobel Prize was also awarded for work in the field of conductive polymers to A. Heeger, A. G. MacDiarmid and H. Shirakawa in 2000.4 Polymer properties may be systematically varied by small changes in monomer composition allowing for great variety. For example, polymers need not be prepared solely from organic monomers and may contain metals. These metals may be introduced to the polymer backbone, pendent to the polymer backbone or be present in the side chain of the polymer. The introduction of this thesis as well as the introductions to each of the experimental chapters will contain basic information pertaining to the nomenclature and  1  chemistry of the studied compounds, the general chemical reactions that were conducted with them as well as an overview of the literature available and a general introduction to the unusual forms, at the undergraduate level, of analysis used. Over the course of this introduction and the more specific introductions found at the beginning of each of the experimental chapters, it will become clear that some areas of research involving cyclopentadienyliron complexes had not yet been investigated when this thesis was begun. These areas included different topographies of polymer such as starshaped, dendrimeric, crosslinked and hyperbranched and different chemical bonds such as esters and amides within the backbone of the polymer. As a result, my research focused on developing these areas and exploring the properties of the resultant compounds prepared. 1.1 Polymer topologies 1.1.1 Linear polymers prepared by condensation polymerization Condensation polymers are those long chained molecules prepared from monomers that contain complimentary functional groups that react to release a small molecule.2 Two scenarios may occur as seen in figure 1.1. The first scenario being that there is one monomer that has two complimentary functional groups attached to it. In this case the monomer would self-polymerize. The second option would be that there are two different monomers, each being bi-functional with complimentary functional groups. Condensation polymers include polyesters, polyethers, polyamides, polyamines and polyurethanes.  2  OH  OH  HO  HO  HO  O  O HO  O  O  HO  O  O  O  OH  OH OH  O O  O  O  O  O  O  O  n  n  (a) (b) Figure 1.1 Polyesters formed by condensation polymerization: (a) self-polymerizable monomer releasing water; (b) use of two complementary monomers, releasing water The method of synthesis for condensation polymers is not overly different than that for the preparation of a small molecule with the same type of linkage. For example, esterification5 may be accomplished using the Fisher-Speier method,6, 7 the acid halide or cyanide6,  8  or via an activating system.6,  9, 10  Esterification resulting in polymerization is  commonly accomplished via a modified Fisher-Speier method involving heating to the melt, usually in the presence of a transition metal catalyst.5,11-19 This method has been used in the preparation of polyesters since the beginning of polymer chemistry.1 The most pronounced difference between the synthesis of a small molecule and a polymer lies in the use of the bi-functional monomer(s) and commonly a very small solvent volume or lack thereof during the reaction.  3  The reaction mechanism of the Fisher-Speier method can be seen in scheme 1.1.7 The addition of a small amount of acid causes protonation of the carboxylic acid. This leaves it prone to attack from the alcohol. After alcoholic attack of the carbonyl carbon, one of the protonated oxygens is lost as water. The remaining protonated oxygen then loses the proton catalyst and the carbonyl group is regenerated resulting in the formation of the ester linkage. A transition metal catalyst works via the same mechanism, that is, by bonding with oxygen. H  H  O  O  O  H+ H R  H  O  R  H  O  1.1 R = aliphatic or aromatic  R  O  1.3  1.2  H H  O  H  O  O H H  R  R  R'  O  O R'  1.5  O  O R'  O  H  H  R  O  1.4  1.6  1.7  H  H  -H2O  H  -H+  O  R'  R  O  1.8  O  R' R  O  1.9  Scheme 1.1  4  The use of an activating agent such as dicyclohexylcarbodiimide (DCC) follows a different mechanism.6 In this, the DCC is converted to dicyclohexylurea (DCU) while the carboxylic acid is activated to react with the alcohol to yield the ester. The reaction mechanism, as seen in scheme 1.2, starts with the formation of a carboxylate, unlike the Fisher-Speier mechanism. The first step is the removal of the proton from the carboxylic acid by the DCC. This is then followed by attack of the carboxylate on the central DCC carbon. Further protonation of the DCC causes increased cationic character of the carbonyl carbon. Attack on this carbon by the alcohol results in a protonated form of the ester and formation of DCU. O H R  O  1.1  N  C  R = aliphatic or aromatic  N  1.10  O R  O  N  1.11  C  H  N  C  H  N  1.12  N  O  1.13  R O  H+ H N  C  H  N  O  R  1.14  O O R'  H  1.5  H O  R  R' N  O  1.15  H  -H+  C O  N H  1.16 O  R  R'  1.17 O  Scheme 1.2  5  Degradation of an ester linkage via base in water is known as saponification.6 This is commonly employed in the recycling and waste disposal of commercial polyesters.20 Oligomers find use as resins and are often repolymerized forming a copolymer. Strong bases are effective, although hydrolysis of the ester may also be carried out using acid.5,6,20 The mechanism of saponification may be seen in scheme 1.3.6,20 Weak bases such as potassium carbonate are not as effective at initiating the breakdown.20 This is beneficial as carbonate is an excellent means of preparing phenolic nucleophiles in situ for the preparation of ethers.21 Etherification reactions rarely utilize water as a reaction solvent thus hydrolysis is unlikely. 1.11 O  1.1 O  O  OR'  R  O  1.17  OH-  H  slow R' R  O OH  R  O R' O1.19  1.18  O-  R  R'  H O 1.5  Scheme 1.3 Another  example  of  condensation  polymers  includes  polyethers.  These  commercially useful aromatic polyethers were introduced to market in the early 1960s.21 These polymers contained both ether and ketone linkages and ushered in the polymer type commonly known as poly(arylene ether)s. Synthesis of these may take place using several methods depending on the starting materials chosen, including: electrophilic aromatic substitution;6,21 nucleophilic aromatic substitution;6,21 various metal coupling reactions7,21 and the Williamson sythesis.6,7 Nucleophilic aromatic substitution reactions have been the best studied method for forming the ether and the thioether bond. The mechanism may be found in scheme 1.4.6, 21  6  In this, Y is an electron withdrawing group, X a leaving group and Nu- the attacking nucleophile. The factor determining the speed of the rate determining step is the electron withdrawing ability of Y. This may be predicted based upon the stabilization of the Meisenheimer intermediate. The nucleophilicity of the attacking group also has an effect upon the rate of formation of the Meisenheimer intermediate. The relative rates are based on the strength of the nucleophile and the rates are as follows: ArS- > RO- > ArO- > OH- > ArHN2 > Cl- > H2O. The choice of leaving group plays less of a role in the rate of the overall reaction as it does not take place during the rate determining step. The relative rates of leaving groups is as follows: F- > NO2- > Cl- > Br- ~ I- > -OAr > -OR > -SR.6, 20 1.20  O  O  X  slow  N  N  X  O  O  O  X N  Nu  O 1.22  Nu  1.23  O fast  Nu  N O  Nu-  X-  1.21  1.24  Scheme 1.4 Both polyesters and polyethers are part of a class of polymers known as engineering thermoplastics.5,21 This class displays high glass transitions, high thermal stability and good mechanical properties. Polyesters find use in the textiles, food packaging and other industries such as fibers, molding resins, and films, whereas polyethers are slightly more limited due to increased temperature requirements.5,21 The most popular polyester is poly(ethylene terephthalate) or PET, followed by Dacron and mylar.5 Poly (ether ether ketone) or PEEK, and poly(ether sulphone) are well known commercial examples of polyethers.21 Polyesters can be easily blended with other polymers allowing easy property modifications post synthesis.5 The preparation of various types of copolymers is also  7  common. These can be readily found in the form of block copolymers, random copolymers or by judicious design of the monomer. An advantage to using polyesters as opposed to other polymers such as polyethers is that polyesters are biodegradable.5 This allows an added application of the medical arts as stents, staples, pins and bone plates which may be recognized and used by the body without rejection during a lifetime. The ease of the degradation of the ester linkage under acidic or basic conditions causing hydrolysis results in an environmentally friendly polymer post consumer use.5 On the other hand, the ether linkage does not easily degrade by hydrolysis or even by oxidation.21 1.1.2 Star-shaped molecules, polymers and dendrimers Star-shaped molecules and dendrimers are a topology of macromolecules with exactly known molecular weights, exactly known structures and a set number of branch points.22,23 Star-shaped polymers are a closely related field.23 For these, linear polymerization starting from a branched core molecule gives the desired polymer with a single branch point. Schematic examples of these may be found in figure 1.2.23 In the case of star-shaped molecules there is one branch point in the centre of the molecule, whereas dendrimers contain a branch point at the centre as well as at set points in the arms.22,23 Starshaped polymers, like star-shaped molecules contain only one branch point at the centre of the polymer, unlike star-shaped molecules they are prepared using standard linear polymerization techniques resulting in average molecular weights.23  8  A  B  C  Figure 1.2 Schematic examples of (A) dendrimer; (B) star-shaped molecule; (C) starshaped polymer Dendrimer chemistry began with the independent publishing of what was initially called cascades, starbursts and arborols as a communication in 1978 and as several papers in 1985/1986 by the research groups of Vogtle,24 Tomalia25,26 and Newkome.27 Since these seminal publications, the field has grown to include star-shaped molecules and star-shaped polymers. The original papers described the synthesis of polyamines24 and polyamides25-27 by the divergent method meaning preparation starting with the core of the molecule and building outwards.22,27 Dendrimer and star-shaped molecules now commonly include polyethers, polyesters, heteroatoms and metals.23,28-33 Preparation may also take place via convergent synthesis, that is, the preparation of the dendrimer or star arms with subsequent attachment to the core to result in the desired molecule (figure 1.3).22,23,28-33  9  Divergent Growth  Convergent Growth  Figure 1.3 Methods of dendrimer growth Divergent syntheses was the first reported method of synthesis.22,28 It does, however, suffer from several drawbacks including the large number of reactions that must occur for each successive generation. If these reactions do not occur, defects in the resultant dendrimer will form. Separation of the defective dendrimers can be difficult and, with purification of each generation, the higher generations can be low yielding. As a result, convergent synthesis was born. This allowed for purification of the arms prior to connection to the core and a decreased chance of defects in the final product.22,28 In most cases, the dendrimers and star-shaped molecules are prepared by a combination of the two techniques. These two methods may be seen in figure 1.3.22 Dendrimers are classified by the linkages that form the branch points as well as the generation (figure 1.4).22,25,26,28 The dendrimer generation may be found by the number of branch points that are found radiating from the central core of the dendrimer. Star-shaped 10  molecules contain only one branch point, that of the central core. First generation dendrimers contain two branch points, that is, the central core plus one branch per arm. A second generation dendrimer would contain three branch points, those of the core plus two branches per arm, and so on for the higher generations.22,25,26,28 Star-shaped or Core  1st Generation  2nd Generation  3rd Generation  Figure 1.4 A schematic of dendrimer generations General properties of dendrimers include: a predictable, spherical shape in which size varies with generation; lower glass transition temperatures resulting in amorphous compounds; viscosity variation with generation, displaying a minimum and a maximum; large number of end groups with a hollow-like interior; and increased solubility with increased molecular weight.22 Star-shaped molecules show similar characteristics based upon molecular weight. Drawbacks to working with dendrimers lie predominately with  11  their synthesis, that is, they require several steps and several purifications to prepare and have, at higher generations defects due to De Gennes dense packing.22 The advantages of dendrimers and star-shaped molecules can be found in their applications. Many examples of them being used in catalysis exist.34-37 The compound may contain a catalyst in the interior of the molecule or on the outer periphery. This catalyst may be bound to the molecule or absorbed within the inner cavity. Metallated dendrimers have also been reported to function as molecular batteries,38,39 sensors40-46 and in medicine as Magnetic Resonance Imaging (MRI) contrast agents47-49 and cancer therapy.49 1.1.3 Hyperbranched polymers Hyperbranched or dendritic polymers are one-pot synthesis of dendrimer-like molecules, that is, highly branched polymeric compounds with irregular structures. P. J. Flory initially predicted them theoretically in the 1940s and early 1950s.50-55 Flory was investigating the physical properties of the polymers prepared by Carothers as well as polymers that had not yet been synthetically prepared such as dendrimers. Flory won the Nobel Prize in Chemistry in 1974 for his work in examining the physical chemistry of macromolecules.4 Due to the random nature of hyperbranched polymers, analysis and characterization can be difficult. Omitting extremely high degrees of polymerization, the generic hyperbranched polymer may be broken down into three main units, terminal, linear and dendritic as seen in figure 1.5.56,57 Each of these areas results from differing numbers of reactions around the branching monomer during polymerization. The dendritic unit results when all available reactive functional groups on the branching monomer have reacted. If only dendritic units occurred in the hyperbranched polymer, a dendrimer would be the  12  result. Linear units/areas in the hyperbranched polymer occur when only two of the possible reactive functional groups on the branching monomer react, resulting in the formation of a linear polymer. If only one of the possible reactive functional groups on the branching monomer reacted, then a terminal unit was formed. A terminal unit is the equivalent of the end group or periphery of a dendrimer. L in e a r  D e n d ritic  T e rm in a l  Figure 1.5 Schematic showing dendritic, linear and terminal units in a hyperbranched polymer Manipulation of the ratios of dendritic to linear to terminal units in the hyperbranched polymer give rise to the degree of branching (DB).50,56-58 This ratio allows calculation of the amount of branched versus linear areas of a hyperbranched polymer to be compared to other hyperbranched polymers. Under ideal conditions the DB is 67% for hyperbranched polymers. Linear polymers have a DB of 0 % and perfect dendrimers have a DB of 100%. If low molecular mass hyperbranched polymers have been prepared equation 1.1 has been suggested to have better accuracy, whereas at high molecular masses, equation 1.2 is more accurate.57 The relative amounts of terminal, linear and dendritic units are often estimated from nuclear magnetic resonance (NMR) values. The degree of polymerization (DP) may also be calculated from the relative amounts of linear, terminal and dendritic  13  units in the hyperbranched polymers (equation 1.3).50,57 In each of the equations, T is for terminal units, L for linear units and D for dendritic units.  2D  DB (%) =  100  2D + L   [1.1]   D +T  DB (%) =  100  D +T + L  [1.2]  DPn =  D + L +T T −D  [1.3]  There are several methods employed in the synthesis of hyperbranched polymers. The most common is that of the self-polymerization of an ABx monomer.56-59 In this method, network polymers do not form but the monomers are rarely available commercially. The second most popular method is that of the polymerization of two monomers of complimentary functionality, that is, the A2 +B3 system.58 The monomers for this are readily available commercially, but the method does suffer from network formation and cyclization/backbiting.58 Hyperbranched polymers may also be prepared via grafting to linear polymers,58,61 ring opening polymerization,56-58 and vinyl polymerization.56-58,61 In attempts to curb the defects of the A2 +B3 synthesis, several variations exist, usually using monomers with complimentary functionalities but differing reactivities or via the addition of another linear monomer to reduce the amount of branching resulting in a decreased likelihood of backbiting and cyclization.58-61 Due to the large amount of branching present in hyperbranched polymers, this topological class tends to be unsuitable for engineered thermoplastics even when polyesters and polyethers are involved.57,58 Some characteristic properties depend on the degree of branching, such as a globular shape and a lack of chain entanglements in the linear  14  portion.56-58 The glass transition temperature tends to be low due to the amount of branching inhibiting crystallization at high temperatures.56,57 As a result, the melting temperatures of hyperbranched polymers also tend to be low.56,58 The glass transition temperature of hyperbranched polymers is affected by the number of end groups, their ability to hydrogen bond and the molar mass of the polymer.57 Viscosity is highly dependent on the method of synthesis and on the chosen monomers and thus varies greatly, although it tends to be low in relation to analogous linear polymers.56-58 The branching also gives a high number of functional groups that may be reacted post-polymerization.56 This large number of unreacted functional groups also allows for increased solubility.56 Commercially, hyperbranched polymers are sold under several trademarked names and generally include poly(ester amides), aliphatic polyethers, aliphatic polyesters and poly(ethylene imines).57 They have found use as crosslinkers, UV-curing precursors and additives for waterborne resins and flexible polyurethane foams.57 Several uses have been suggested in the scientific literature, including controlled release agents,56-58,62,63 coatings,56-58 dental composites for dentures,56,57 lubricants,57,64 and catalysts.56-58,65  1.2 Water-soluble polymers Water-soluble polymers contain water-soluble functional groups such as amines, amides, carboxylic acids, carboxylates, sulphates, phosphates and aliphatic ethers.66,67,68 Naturally occurring water-soluble polymers have specific uses and include DNA, RNA, proteins and enzymes as well as polysaccharides.66 For example, the enzyme 1aminocyclopropane-1-carboxylate oxidase (ACC Oxidase) is known to cleave carboncarbon bonds of ACC in the presence of diatomic oxygen to give ethene, carbon dioxide, hydrogen cyanide and two molecules of water.69 This enzyme, like several other enzymes  15  functions via a non-heme iron stabilized by two histidines and one carboxylic amino acid in facial formation around an octahedral iron.69,70 Synthetic water-soluble polymers are commonly prepared via the use of polyelectrolytes and ionic functional groups.66,68 Watersoluble polymers may be linear, branched or dendritic in structure and may also be prepared as copolymers with either water-soluble or non-water-soluble copolymers.66 The synthesis of water-soluble polymers may occur via the routes used by nonwater-soluble polymers so long as the monomers are soluble in water.67,68,71As a result, free radical initiators and cationic or Friedel-Crafts type initiators may be used.67,71 Emulsion or biphasic polymerization techniques may also be used, especially if preparing a copolymer in which one of the monomers is not water-soluble.68,71 Water solubility of the polymer may also be introduced via post-polymerization modification to introduce water-soluble functional groups.67 The most common application of water-soluble polymers is in the medical arts. To this end, they have been suggested and used predominately for drug delivery,49,68,71-83 and to a lesser extent for removal of toxic compounds from the body,73 as MRI contrasting agents,47-49 and for antimicrobial activity.79-81 A proposed industrial application involving a reduction in oil viscosity following the addition of a water soluble polymer has been reported.84  1.3 Incorporation of metals into polymers Metals may be incorporated into polymers via several different methods. For example, they may be present in the backbone, pendent to the backbone or in a side chain of the polymer. The method of attachment of the metal to the polymer also varies. The metal may be sigma or pi bonded to a carbon or a heteroatom.85-88 These bonds may also  16  range from metallic to covalent to purely ionic depending on the metal and the ligand choice.85 The metal may or may not be important for the integrity of the polymer, that is, the effects of metal removal vary from collapse of the polymer backbone to monomer to modifications to the polymer properties.  1.3.1 Metal coordination The strength to which ligands bind to metals may be found based upon the metal, the ligand and spectroscopic information.85-89 The orbitals that are used for bonding are based upon ligand-field theory and require symmetry operations and molecular orbital energy diagrams to assign.86-88 In crystal-field theory, ligands have been ranked based upon energy transitions that occur when they are present in a complex. The metal to which the ligand is coordinated to also has an effect on the strength of the bond that is formed.86-88 Chelation may occur when the ligand of choice contains two or more groups capable of binding with the metal and a ring is formed.89 Common chelating groups for metals include carboxylic acids, phenols, thiols and amines. The formation of a five or six membered ring is common for bidentate ligands. Control over which groups may bind in a bidentate ligand with two different coordination groups may be governed by pH and ionic radius of the metal.89 The coordination and chelation of metal atoms has allowed for the formation of conducting polymers,90 controlled hydrogen bonding in supramolecular compounds,91 and the analysis of metal ions in natural water samples.92,93  1.3.2 Cyclopentadienyliron complexes Metallocene chemistry first began with the discovery of a compound whose name was proposed to be ferrocene in 1952.94 Several derivatives of ferrocene were reported  17  shortly after its preparation, usually involving substitution95,96 of a proton from the cyclopentadienylion rings to contain a carboxylic acid, an amide, an amine, various alkyl groups or the vinyl group and also bisferrocene salts.97,98 Preparation of poly(vinyl ferrocene)95 was accomplished in 1955 and polyferrocene98 in 1972. The 1973 Nobel Prize in chemistry was awarded to Fisher and Wilkinson for the study of organometallic sandwich compounds.4 Cyclopentadienyliron complexes may be prepared using ferrocene as a starting material according to a method by the research group of Nesmeyanov and Vol’kenau.99-102 Synthesis of these compounds occurs via the production of a ferrocenonium ion from the ferrocene in the presence of aluminum chloride, aluminum powder and the desired arene.99102  The ligand exchange102 between one of the cyclopentadienylions and an arene follows  that of a Friedel-Crafts mechanism (scheme 1.5).7 AlCl3 NH3 1.29 NH4+  AlCl3 Fe  AlCl3  1.27  Al-Cl3  Fe  Fe+  1.28 1.25  1.26 1.30  1.32  Fe+PF6-  PF6-  Fe+  1.31  Scheme 1.5  18  Bonding within ferrocene and η6-arene-η5-cyclopentadienyliron complexes has been previously studied and may be seen in figure 1.6.86,88,103-107 In the case of complexes in which both cyclopentadienylion groups have been substituted, the symmetry is D6d while staggered and D6h when eclipsed.103 Iron forms e”1 molecular orbitals from the 3dyz and 3dxz that allow the donation of electrons from the aromatic rings.103-106 Also formed by the iron are e’2 orbitals from the 3dxy and 3dx2-y2 that participate in back bonding to the aromatic rings.103-106 Ferrocene displays D5d symmetry while staggered and D5h symmetry when eclipsed with an a’1 orbital alon with the e”1 and e’2 orbitals.88,103,105-107 low spin octahedral diamagnetic t2g6eg0  high spin octahedral paramagnetic t2g4eg2  dyz dxz  dyz dxz dz2  dz2  dx2-y2 dxy  dx2-y2 dxy (a)  (b)  Figure 1.6 Orbital diagram for octahedral complexes where (a) is the stable form of iron in ferrocene and (b) is unstable86,88 It has been estimated that approximately 65% of the electron density is centered on the arene whereas the cyclopentadienyl group only has 11% and iron 24% of the electron density.105 The presence of electron withdrawing substitution on the aromatics cause an increase in the amount of back bonding while electron donating substitution decrease the amount of back bonding via e’2 orbitals that are of higher energy than those directly  19  involved in bonding. Complexes will not form if the number of electron withdrawing substitutions are too high/strong due to the required amount of back bonding being more than the iron is able to supply.105 These orbitals give rise to a crystal field splitting pattern with three spin allowed d-d transitions and a spin-forbidden transition while the iron is in low spin.103 If the iron is high spin, electrons are present in the antibonding orbitals as opposed to the bonding and non-bonding orbitals thus inhibiting complex formation.88 Due to the presence of the complexed iron, the aromatic signals in the proton and carbon NMR spectra are shifted.102,108-114 As a result, aromatic protons normally appearing in the range of 7-8 ppm in an uncomplexed aromatic shift to the range of 6-7 ppm when complexed102,108-114 due to back bonding with the iron e’2 orbitals.104 Restricted rotation around an arene-subsitution bond in the presence of bulky groups ortho to the substitution and the cyclopentadienyliron unit has been reported to cause favoured interactions and couplings with only one side of the arene ring.113, 114 Removal of the bulky groups allows for free rotation around the arene-substitution bond in the presence of the cyclopentadienyliron moiety.113, 114 The cyclopentadienylion shifts from around 4 ppm in ferrocene to the range of 5-5.5 ppm in η6-arene-η5-cyclopentadienyliron complexes. This is due to the electronic donation of the cyclopenadienylion group to the iron e”1 orbitals.104 Complexed carbons also display a shift from the aromatic region around 120 ppm to approximately 75 ppm. This allows for easy identification and analysis of cyclopentadienyliron containing compounds in the proton and carbon NMR spectra. The η6-arene-η5-cyclopentadienyliron complex can undergo reactions depending upon the substituents on the aromatic rings.115-118 Nucleophilic aromatic substitution reactions118-122 for the formation of aromatic ethers is one of the more common  20  reactions.120-122 The effect of the iron complex acts as an electron withdrawing group allowing for the reaction to be conducted at ambient temperatures and pressures.121-123 Polymers containing cyclopentadienyliron complexes can be easily prepared as a result of this reaction.121,124-129 A benefit of polymers containing the cyclopentadienyliron cation includes an increase in the solubility of the polymer as well as gentler reaction conditions during synthesis in relation to the preparation of the purely organic polymer.121,127,128,130-134  Other  proposed  uses  of  η6-arene-η5-cyclopentadienyliron  containing compounds take advantage of iron’s redox capability and include electrode modification, batteries, electron reservoirs, sensors, and catalytic behaviour.121,127-129,133-141 Reports of η6-arene-η5-cyclopentadienyliron compounds being used as azobenzene dyes142 and phase-transfer agents for radioactive wastes143 may also be found. Later removal of the metal by decomplexation may be accomplished via photolysis (degradation by light) or thermoloysis (degradation by heat) leaving the organic analog of either the polymeric compound or an organic precursor.118,121,127,129,144-150 Various  η6-arene-η5-cyclopentadienyliron  containing  monomers/monomer  precursors have been used multiple times by the Abd-El-Aziz research group.136,141,151-154 Compound 1.33 may be prepared via a nucleophilic aromatic substitution reaction136,141,151154  at room temperature between 4,4-bis(4-hydroxyphenyl)valeric acid where as  compounds 1.39a,b have been previously prepared via an indirect route135,151,155 as seen in scheme 1.6. The usage of these organometallic precusors and monomers allows for the easy preparation of organic polymers via two steps, namely organometallic polymer formation followed by demetallation.  21  HO  O  Cl  Cl  O  Fe+PF6-  Fe+PF6-  O  1.33  HO  H H2N  1.35  1.34  O  Benzene HO  N  1.36 1)K2CO3, DMF R  Cl  2) 30% HCl  1.37a, R = H b, R = CH3  Fe+PF6-  H R O  Fe+PF6-  O  1.38a,b CrO3, Acetone OH  R O  Fe+PF6-  O  1.39a,b  Scheme 1.6 Removal of the cyclopentadienyliron unit may be accomplished via pyrolysis, electrolysis or photolysis.121 Pyrolysis may occur in the solid or solution state so long as the 22  solvent boils above 200 oC and electrolysis potentials for demetallation tend to be in the range of -1.50 to -2.00V.121 Photolysis is the most common method used for cleavage of the cyclopentadienyliron unit and may be seen in scheme 1.7. The cyclopentadienyliron complex is first exited by a photon causing an electron to be promoted to an antibonding orbital from a bonding or non-bonding orbital. This high spin, triplet state causes destabilization of the iron-arene bond followed by ring slippage. The iron may then be coordinated by solvent, commonly acetonitrile. Upon sufficient coordination, the arene is released and may be removed from various iron salt impurities by column chromatography or extraction with washing.121 *  hv Fe+  Fe+  Fe+  1.41 triplet state  1.40  1.42 CH3CN 1.43  Fe+ NCCH3  1.44 2 equiv 1.43 [CpFe(NCCH3)3]+ 1.45  + Arene 1.46  Scheme 1.7  23  1.4 Instrumental methods not commonly studied during undergraduate 1.4.1 Polarized optical microscopy (POM) Polarized Optical Microscopy (POM) is also known as polarized light microscopy. It is an older technique used to visually identify refractive indices and more commonly, differentiate between isotropic and anisotropic samples.156-158 Isotropic samples do not interact with polarized light as they only have one refractive index in all directions. Anisotropic samples do interact with polarized light and display multiple refractive indices allowing for birefringence. The observation of refractive index changes and birefringence patterns such as spherulites allows for identification of sample characteristics such as phase changes in the presence of different temperature regimes or nucleating agents. The light polarizers may be removed from the microscope for the observation of samples under ordinary light. This allows for the identification of properties such as thermochromism as opposed to liquid crystallinity.156-158  1.4.2 Viscometry Viscosity in liquids is commonly defined as resistance to flow due to friction when there is an applied force.159-165 It is given the symbol η whereas its reciprocal is known as fluidity. Measurements require laminar or Newtonian flow and the value is most often measured in centipoises (cP, gcm-1s-1). The viscosity of solutions in known to have a dependence on pressure and will increase with decreasing temperature. The functional groups present within the molecule also affect the viscosity of the solution. When there are more interactions (e.g. hydrogen bonding, dipoles) between the molecules, the amount of energy required to maintain laminar flow increases resulting in an increased viscosity.195-165  24  The term viscoelastic refers to the ability of a chain to repeatedly stretch and deform while still exhibit flow and motion in either the melt or solution form.159 There are several different viscosity values that may be reported for solutions.160-167 The relative viscosity takes into account the solvent of the solution and has the abbreviation ηr. This may be calculated as seen in equation 1.4, where η is the measured viscosity of the solution at a given concentration and ηo is the viscosity of the solvent.  ηr =  η ηo  [1.4]  Viscosity is commonly reported as the inherent viscosity, ηinh at a particular concentration, usually 0.5 g/dL.161 In cases where the viscosity can not be measured at the given concentration, the value is calculated via the equation of the line formed by plotting the concentration versus measured inherent viscosity values. The calculation of ηinh may be seen in equation 1.5, where c refers to the concentration.160-163,165-167 Although this value is unit less, the units pertaining to the reduced viscosity and the mass concentration are suggested to be used by the International Union of Pure and Applied Chemists (IUPAC).165  ηr    c   η inh = ln  [1.5]  Graphing the inherent viscosity versus the concentration resulted in a linear relationship for neutral compounds. However, when a charged compound is graphed, there is a sharp increase in the inherent viscosity at dilute concentrations.167-173 This is known as the polyelectrolyte effect and it refers to an increase in the hydrodynamic volume at dilute solutions due to formation of an ion sphere. This charged ion sphere causes increased interactions between the molecules in the dilute solution which, in turn, causes the viscosity to increase. As the solution becomes more concentrated, the ion sphere reduces in size and  25  disappears as the solution becomes more ionic resulting in a marked decrease in the measured viscosity with increasing concentration of electrolyte.167,168 The viscosity of the solute at a specific concentration may be determined via the specific viscosity (ηsp) as is seen in equation 1.6. In this, the relative viscosity may be used to determine the specific viscosity.160-163,165-167  η sp =  η −ηo η ηo = − = ηr −1 ηo ηo ηo  [1.6]  The effect of concentration on the viscosity may be taken into effect via calculation of the reduced specific viscosity, ηred, where the mass concentration of the solution is given by ρ. This may be calculated using equation 1.7.160-163,165-167   1  η − η o   1   =  η sp η red =    ρ  η o   ρ   [1.7]  Intrinsic viscosity, [η], is the change in the viscosity of the solution at infinite dilution. Like inherent viscosity, the intrinsic viscosity is suggested to have the units of volume per mass (i.e. mL/g).165 This value may be calculated via the equation of the line that is resultant by graphing of the reduced viscosity versus concentration or by equation 1.8.160-167,171 This type of graph is known as a Huggins plot.160,161,166,167,171 When the solvent used to test the viscosity is ideal, the extrapolation of the natural log of the relative viscosity versus the concentration to a concentration of zero will give the same value for the intrinsic viscosity. The plot of lnηr versus the concentration is called a Kramer plot.160,161,166,167 Most intrinsic viscosity values reported are derived from the Huggins plot and equation. Linear polystyrene has been reported to have [η] of 0.049 dL/g with an Mw of 5110 g/mol and [η] of 0.126 dL/g with a Mw of 19000 g/mol in THF.174 Polystyrene fractals with molecular weights between 4.96 x 105 to 3.07 x 106 gave [η] between 0.044  26  to 0.090 L/g.169 Upon sulphonation, these same fractals showed an increase in [η] to 0.139 to 0.182 L/g.169  [η ] =  lim  1  η − η o   ρ → 0  ρ  η o  lim   = η red  ρ → 0  [1.8]  When polyelectrolytes are graphed to give the Huggins and Kramer equations, the lines are non-linear in the polyelectrolyte region. Removal of this region may be accomplished visually, but it is arbitrary. As a result the inherent viscosity may be found using the Fuoss equation and plot.167,171-174 In the Fuoss plot, the reciprocal of the reduced viscosity is plotted against the square root of the concentration to give a straight line. The inherent viscosity (A) is the reciprocal of b where the equation of the line is in the form of y = mx + b. The Fuoss equation may be seen as equation 1.9 when in the form of the equation of the line from the plot. B is a constant relating to the compound in a particular solvent/temperature system.167,171-174  c  η sp  =  B 1 c+ A A  [1.9]  The intrinsic viscosity may be used to calculate molecular weights as well as make approximations in regards to the shape of the molecules in question. The relationship between [η] and molecular weight, M, is known as the Mark-Houwink equation and it may be seen in equation 1.10.160-166,168-170,174-176  [η ] = kM rα  [1.10]  Plotting the log of the intrinsic viscosity versus the log of the molecular weight should give a straight line. From the equation of the line (y = mx + b), the constants k and α may be determined. The constant k is found from the antilog of b and α from the slope m. Values for k range from 10-1 to 10-4mL/g for flexible organic neutral molecules.164,170,174-177 27  The general shape of the molecule is derived from the value of α. Hyperbranched polymers in good solvents174 have values below 0.4. Coiled chains have been found to give values between 0.6 and 0.75, whereas elongated chains give values above 1.3. When α = 0 or is near 0, the molecule is spherical in nature.160,161,162,174 Linear polystyrene has been reported to have k = 39 x 103 cm3mol1/2g-3/2 (European units) and α equal to 0.58 when the solvent was butanone at 25oC.160 Linear polystyrene in THF at 30oC has been reported to display an α of 0.73, whereas star-shaped polystyrene had α equal to 0.68 and hyperbranched polystyrene showed α to be 0.39 under the same conditions.174 Spherical molecules display a non-linear increase in hydrodynamic volume with increasing molecular weight. This gives rise to a situation where the intrinsic viscosity does not change with increasing molecular weight and the Mark-Houwink equation/graph may no longer be used to estimate molecular weight.175 This has been characterized for dendrimers and branched dendrons graphically via comparison of inherent viscosity versus molecular weight. At low generations, the inherent viscosity is seen to increase as expected for linear molecules and at higher, more spherical generations, the inherent viscosity decreases. Once the intrinsic viscosity and reduced viscosity are known, the Huggins constant or coefficient, kH, may be determined. This constant gives information regarding binary hydrodynamic events and is dependent on the temperature and solvent in which a particular polymer is tested in.160,161,165,169 Cross-linked sulphonated polystyrene fractals with molecular weights between 4.96 x 105 and 3.07 x 106 gave Huggins constants between 0.2 and 0.9.169 The lower molecular weight fractal gave a lower Huggins constant. Values near 0.99 tend to act as hard spheres whereas values closer to 0.35 are indicative of linear  28  polymers.167 The Huggins constant may be determined by equation 1.11, where c is mass concentration.  η red = [η ] + k H [η ]2 c  [1.11]  The Kramer constant may also be calculated once the inherent viscosity and the intrinsic viscosity are known.160,161,166,167 Values near 0.50 are reported for hard spheres and random coils give values around -0.15. Traditionally for linear neutral polymers,167 the addition of the Kramer constant and the Huggins constant should give a value of 0.5. The Kramer equation is seen below, where kK is the Kramer constant (equation 1.12). ln (η rel ) 2 = [η ] − k K [η ] c c  [1.12]  Using the Einstein viscosity law, the viscometric radius of the dissolved compound may be determined.165,169,174-176 In this equation (1.13), the compound is assumed to be a hard neutral sphere. Modification of equation 1.13 to directly pertain to electrolytes requires a perturbation correction beyond the scope of general mathematics.169 A linear polystyrene polymer of approximately 8300 g/mol gave a viscometric radius of 2.08 nm, while an eight armed star of approximately 74000 g/mol had a radius of 6.0 nm.174 The viscometric radius has the symbol Rη, while NA is Avogadro’s number. 1  Rη = (3[η ]M ) 3 (10π  1  A  )− 3  [1.13]  Application of Einstein’s viscosity law to a particular polymer may be accomplished via substitution with the Mark-Houwink equation (1.10).176 This new equation (1.14), allows for the determination of the hydrodynamic radius of the dissolved compound in the solvent, RH. This value may differ from Rη as it is specific to the compound of interest and the units of length are dependent on k.  29   3kM R H =   10π  α +1  A      1 3  [1.14]  The molecular shrinkage between the linear and branched molecules of similar molecular weights may be determined as may the molecular compactness.161,165,174 The shrinking factor g gives the geometrical shrinkage and expansion of the molecule (equation 1.15)161,165,174 whereas shrinking factor h is related to hydrodynamic size (equation 1.16).174 The shrinking factor g is usually calculated from the radius of gyration although the use of intrinsic viscosity has also been reported.161 Shrinking factors for polystyrene have been previously reported. For hyperbranched polystyrene polymers,174 g ranged from 0.104 to 0.148 while h ranged from 0.44 to 0.56. Shrinking factor h has been calculated between 0.75 to 0.81 for star-shaped polystyrene polymers.174 The molecular compactness, ρ, allows the difference between the dimensions and the molecular geometry to be established for a particular compound (equation 1.17).174 Polystyrene polymers174 that were linear in nature have been reported to molecular compactness ranging between 0.73 to 0.78 while hyperbranched polystyrenes reported 0.971 and 1.043. Molecular compactness is expected to be greater than one when working with high generation dendrimers and stars with many arms. Values below one are expected for stars with few arms, linear polymers and low generation dendrimers.174 The three equations relating to molecular size may be seen below. 2 [η ] sbranched g= 2 = branched [η ]linear s linear  h=  (R ) (R )  η branched  [1.15]  [1.16]  η linear  30  ρ=  Rη  =  Rη  ( R ) (R ) 2 g  1 2  2 H  1 2  [1.17]  Commonly viscosity measurements are done in conjunction with other methods of molecular weight determination such as gel permeation chromatography (GPC) with refractive index and light scattering detectors.164,170,174-177 GPC, like viscometry, depends on hydrodynamic volume and calibration. It is also dependent on the interactions between the polymer and the column packing gel.164 Problems with finding suitable standards for calibration of the GPC to new polymers, especially branched polymers are well known. For example, a column calibrated using linear polystyrene was used to analyze star-shaped polystyrene. The molecular weights by GPC were underestimated by up to 90% when compared to molecular weights calculated by light scattering techniques.176 As a result, values are reported relative to an unrelated commercial standard such as polystyrene and often do not reflect the true molecular weight of the new polymer.164  31  2 Linear polymers containing cyclopentadienyliron moieties as well as ether, ester and thioether linkages 2.1 Introduction One method for the preparation of linear polymers is using nucleophilic aromatic substitution reactions between two di-functional monomers or starting materials. Examples of these include polyethers, polythioethers and polyesters. The monomers of these linear polymers may include areas that are aromatic or aliphatic. These linkages have been used to create various well known engineered thermoplastics such as poly(ethylene terephthalete) or PET and poly(2,6-naphthalate-co-1,4-benzoate) or polyester LCP which displays liquid crystalline properties in the melt.5 Viscosity measurements are often used to compare molecular weights of copoly(ester ether). Molecular weights range drastically based upon the method of synthesis and the comonomers chosen. In the case of a poly(ether ester) prepared by esterification of an etheric aromatic monomer, the weight average molecular weights were in the range of 16 500 g/mol and the number average molecular weights were reported in the range of 8 800 g/mol.9 These values are higher than those reported within this thesis using nucleophilic aromatic subsitution to achieve the poly(ether ester). Thermochromism, or the changing of colour with a change in temperature156 has been shown to occur in iron containing compounds.178-189 This property has predominately been attributed to a spin transition and/or crossover between high and low spin in iron178-186 containing octahedral complexes containing nitrogen based ligands.182,184-188 Structural changes within the iron containing molecule as well as shifts in the electronic state of the bound ligands have been reported to cause thermochromism.187-190 Liquid crystallinity has  32  been reported for polymers prepared via iron-mediated synthesis9 and for chromium complexes. Linear polymers containing cyclopentadienyliron complexes have been reported to be thermally stable to 205-270 oC and show glass transition temperatures between 140-180 oC.137,151,191,192 Previously reported inherent viscosity values for linear cyclopentadienyliron containing polymers were in the range of 25-42 cm3/g.193 Within this chapter, polymers containing cylcopentadienyliron have been prepared with the ester, ether or thioether linkage from monomers containing either aliphatic or a mixture of aliphatic/aromatic regions. The introduction and alteration of aliphatic/aromatic regions was hoped to give liquid crystalline/thermochromic properties. The presence of the ester linkage was hoped to give potential degrability of the polymer while still mintaining the desired thermal properties introduced by the use of the ether and thioether linkages. The polymers were demetallated using photolysis to examine the influence of the metal on the polymer’s properties. The monomers, metallated polymers and demetallated polymers were analyzed thermally using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) as well as spectroscopically with nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy. The molecular weights of the metallated polymers were also determined using viscosity and compared to the molecular weights of the demetallated polymers determined via gel permeation chromatography (GPC) in tetrahydrofuran.  2.2 Results and discussion 2.2.1 Synthesis and properties of cyclopentadienyliron containing monomers As shown in scheme 2.1, several steps were required to prepare the cyclopentadienyliron containing monomers. The initial step was the reaction of the iron complex (2.1) and the phenolic carboxylic acid (2.2) to give the metallated carboxylic acid  33  complex (2.3). Various diols (2.4a-h) were then esterified with the metallated carboxylic acid giving bimetallic compounds with free and reactive chloro-groups that are suitable for polymerization reactions. Monomer analysis (2.5a-h) was done with 1H and 13C NMR, IR spectroscopy, TGA and DSC. O Cl  Cl -  HO OH  F6P+Fe 2.2 60o, 16 hr DMF/THF  2.1  O Cl  OH M=Fe+PF6-  O  M  2.3  HO  2.4a, x = 2; c, x = 4; e, x = 8; g, x = 10;  OH  b, x = 3; d, x = 6; f, x = 9; h, x = 12.  x  DCC/DMAP DCM/DMSO, 16 hr O Cl  O O  M  2.5a-h  O  O  M  x O Cl  Scheme 2.1 1  H and  13  C NMR spectral analysis confirmed that the chloro-capped carboxylic acid  complex, 2.3, was indeed mono-substituted, that is, still having a free chlorine for future reaction. This may be seen in figures 2.1 and 2.2 and the data summarized in table 2.1. As can be seen for compound 2.3, the cyclopentadienyl protons resonates at 5.43 ppm in the 1  H NMR spectra. The complexed aromatic protons were visible as doublets at 6.64 and  6.88 ppm with J coupling of 6.6 Hz. The aromatic protons also appeared as a set of doublets with J coupling of 8.6 Hz at 7.45 and 8.18 ppm. The carboxylic acid was not  34  visible in the proton NMR and thus the region is not shown in figure 2.1. The peaks around 3 ppm are due to the presence of water in the sample being split into two due to hydrogen bonding with the samples carboxylic acid. Residual acetone in the deuterated solvent appears at 2.04 ppm and was used to reference the sample.  Figure 2.1 1H NMR spectrum of compound 2.3 in acetone-d6 (at 200 MHz) The carboxylic carbon of monomer 2.3 was however present in the  13  C NMR  spectrum with a shift of 166.58 ppm. The uncomplexed aromatic carbons were at 121.03 and 133.17 ppm and the quaternary uncomplexed aromatic carbons were at 132.43 and 158.01 ppm. The cyclopentadienyl carbons resonated at 80.69 ppm with the complexed aromatics bracketing it at 78.39 ppm and 87.98 ppm. The quaternary complexed aromatics were found at 105.27 and 129.33 ppm. The strong resonances at 29.9 ppm and 206.7 ppm are due to residual acetone in the deuterated solvent. This may be seen in figure 2.2 with both proton and carbon shifts found in table 2.1.  35  Figure 2.2 13C APT NMR of compound 2.3 in acetone-d6 (at 200 MHz) Table 2.1 NMR shifts for compound 2.3 in acetone-d6 (* quaternary carbons) Cp Complexed Aromatics Aromatics Carboxylic Acid 1 H 5.43 (s, 5H) 6.64 (d, J=6.6 Hz, 2H), 7.45 (d, J=8.6 Hz, 2H), --NMR 6.88 (d, J=6.6 Hz, 2H) 8.18 (d, J=8.6Hz, 2H) 13 C 80.69 78.39, 87.98, 105.27*, 121.03, 132.43*, 166.58 NMR 129.33* 133.17, 158.01* In the 1H NMR spectra of monomer 2.5d, the two methylenes next to the ester linkage were visible at 4.36 ppm. The central methylenes were at 1.57 ppm and the remaining two CH2 appeared at 1.83. The appearance of only three aliphatic resonances illustrates the symmetry in the molecule. The sample contained residual ether from washing as seen by the peaks just below 4 ppm and just above 1 ppm. The cyclopentadienyl protons, both sets being symmetrically the same, appeared as a singlet at 5.41 ppm. The complexed aromatics appeared as two doublets at 6.62 and 6.87 ppm, both with coupling of 7.0 Hz. The uncomplexed aromatics were visible at 7.45 and 8.17 ppm with J coupling of 8.6 and  36  9.0 Hz, respectively. It should be noted that the triplet like appearance of the reported singlets are due to the presence of spinning side bands and the strong peak at 2.04 ppm due to residual acetone in the deuterated solvent. This maybe seen in figure 2.3 with values for all monomers found in table 2.2. Table 2.2 1H NMR values, IR and yields for monomers 2.5a-h (run in acetone d-6 at 200 MHz instrument unless denoted by †, then at 300 MHz). §Due to oiliness of the samples, preparation of KBr pellets was not possible and salt plates were not available for use Yield Aliphatics Cp Complexed Aromatics Carbonyl by (%) Aromatics IR (cm-1) 46 4.73 (s, 4H) 5.41 6.62 (d, J = 6.6 Hz, 7.46 (d, J = 1721 2.5a (s, 4H), 6.86 (d, J = 7.0 8.6 Hz, 4H), 10H) Hz, 4H) 8.19 (d, J = 8.6 Hz, 4H) 1.80 (s, 5.37 6.58 (d, J = 6.4 Hz, 7.42 (d, J = ---§ 2.5b† 79 2H), 4.41 (t, (s, 4H), 6.82 (d, J = 6.6 8.6 Hz, 4H), 4H) 10H) Hz, 4H) 8.14 (d, J = 8.4 Hz, 4H) 72 1.81 (s, 5.40 6.61 (d, J = 6.3 Hz, 7.45 (d, J = 1715 2.5c 4H), 4.43 (t, (s, 4H), 6.86 (d, J = 6.6 8.6 Hz, 4H), 4H) 10H) Hz, 4H) 8.17 (d, J = 8.2 Hz, 4H) 79 1.57 (s, 5.41 6.62 (d, J = 7.0 Hz, 7.45 (d, J = 1715 2.5d 4H), 1.83 (s, 4H), 6.87 (d, J = 7.0 8.6 Hz, 4H), (s, 4H), 10H) Hz, 4H) 8.17 (d, J = 4.36 (t, 4H) 9.0 Hz, 4H) 69 1.44 (br s, 5.41 6.61 (d, J = 6.6 Hz, 7.45 (d, J = 1714 2.5e 8H), 1.79 (s, 4H), 6.86 (d, J = 6.6 8.6 Hz, 4H), (br s, 4H), 10H) Hz, 4H) 8.16 (d, J = 4.33 (t, 4H) 8.2 Hz, 4H) 1.43 (br s, 5.36 6.58 (d, J = 6.6 Hz, 7.42 (d, J = ---§ 2.5f† 91 10H), 1.76 (s, 4H), 6.82 (d, J = 6.8 8.4 Hz, 4H), (br s, 4H), 10H) Hz, 4H) 8.13 (d, J = 4.29 (t, 4H) 8.2 Hz, 4H) 55 1.36 (br s, 5.40 6.60 (d, J = 6.6 Hz, 7.44 (d, J = 1715 2.5g 12H), 1.77 (s, 4H), 6.85 (d, J = 6.3 7.8 Hz, 4H), (br s, 4H), 10H) Hz, 4H) 8.16 (d, J = 4.32 (t, 4H) 8.3 Hz, 4H) 84 1.32 (br s, 5.40 6.61 (d, J = 4.3 Hz, 7.45 (d, J = 1716 2.5h 16H), 1.77 (s, 4H), 6.84 (d, J = 4.2 7.8 Hz, 4H), (br s, 4H), 10H) Hz, 4H) 8.16 (d, J = 4.32 (t, 4H) 7.4 Hz, 4H)  37  Figure 2.3 1H NMR spectrum of compound 2.5d in acetone-d6 (at 200 MHz) The 13C NMR of monomer 2.5d may be seen in figures 2.4 and 2.5, data for each of the monomers prepared found in tables 2.3a and 2.3b. When acetone-d6 was used as a NMR solvent, overlap was found to occur between the solvent residue peak used to reference the spectrum and the aliphatics of the monomers. Acetone residue appears at 29.9 ppm and 206.7 ppm whereas DMSO at 39.5 ppm. Table 2.3a 13C NMR values for 2.5a-h in acetone-d6 (200 MHz unless denoted by †, then at 300 MHz)(*quaternary carbons) Aliphatics Cp Complexed Aromatics Carbonyl 80.52 78.24, 87.74, 120.91, 128.30*, 165.53 2.5a 63.67 105.06*, 131.91* 132.91, 158.03* 80.65 78.31, 87.93, 120.99, 128.95*, 165.70 2.5b† 25.70, 63.60 105.18*, 132.16* 132.84, 157.91* 25.60, 65.31 80.30 77.99, 87.56, 120.71, 128.30*, 165.85 2.5c 104.85*, 131.63* 132.67, 157.72* 80.40 78.04, 87.62, 120.81, 128.84*, 165.59 2.5d 26.03, 65.47 105.02*, 132.16* 132.67, 157.79* 25.92, 65.31 80.20 77.78, 87.43, 120.56, 128.36*, 165.17 2.5e 104.61*, 131.55* 132.36, 157.29* 80.33 78.00, 87.61, 120.68, 128.71*, 165.40 2.5f† 26.03, 65.21 104.91*, 131.89* 132.46, 157.63* 87.69, 120.85, 128.78*, 165.45 2.5g 26.32, 29.56, 80.48 78.10, 65.50 105.00*, 131.94* 132.66, 157.69* 87.81, 120.78, 128.45*, 165.14 2.5h 26.11, 26.52, 80.52 78.15, 28.84, 29.63, 104.74*, 131.66* 132.51, 157.37* 65.43  38  Table 2.3b 13C NMR values for 2.5a-h in DMSO-d6 (200 MHz unless denoted by †, then at 300 MHz)(* means quaternary carbon) Aliphatics Cp Complexed Aromatics Carbonyl 79.41 77.31, 86.70, 120.14, 126.91*, 164.63 2.5a 62.93 103.87*, 130.44* 131.89, 157.08* 78.94 76.75, 86.26, 120.90, 127.00*, 164.30 2.5b† 28.82, 67.88 103.42*, 130.14* 131.34, 156.67* 24.98, 64.60 79.60 77.30, 86.88, 120.36, 127.56*, 164.93 2.5c 104.05*, 130.81* 132.02, 157.01* 86.78, 120.27, 127.56*, 164.83 2.5d 25.09, 28.00, 79.50 77.18, 64.79 103.95*, 130.74* 131.88, 156.89* 25.28, 28.01, 79.47 77.25, 86.77, 120.27, 127.47*, 164.78 2.5e 28.44, 64.79 103.92*, 130.66* 131.80, 156.92* 87.43, 120.89, 128.06*, 165.37 2.5f† 25.91, 28.65, 80.07 78.03, 29.09, 29.30, 104.52*, 131.23* 132.42, 159.57* 65.38 87.05, 120.34, 127.48*, 164.83 2.5g 25.41, 28.10, 79.77 77.42, 28.60, 28.95, 103.99*, 130.65* 131.90, 156.85* 64.93 86.55, 121.04, 127.12*, 164.38 2.5h 25.03, 27.74, 79.24 77.01, 28.26, 28.54, 103.60*, 130.32* 131.47, 156.56* 28.55, 64.48  In the case of 2.5d, only two of the three CH2 appeared in the acetone solution spectrum at 26.03 and 65.47 ppm as may be seen in figure 2.4. Whereas in the DMSO solution spectrum, the expected three CH2 resonances appeared at 25.09, 28.00 and 64.79 ppm (figure 2.5). The cyclopentadienyl carbons appeared at 80.40 ppm in acetone and at 79.50 ppm in DMSO. The complexed aromatic CHs bracketed the cyclopentadienyl carbons and were found at 78.04 and 87.62 ppm in acetone and 77.18 and 86.78 ppm in DMSO. The quaternary complexed carbons were found at 105.02 and 132.16 ppm in acetone and 103.95 and 130.74 ppm in DMSO. The aromatics were visible at 120.81 and 132.67 ppm in acetone and 120.27 and 131.88 ppm in DMSO. The quaternary aromatics resonated at 128.84 and 157.79 ppm in acetone and 127.56 and 156.89 ppm in DMSO.  39  Finally, the carbonyl carbon appeared at either 165.59 ppm in acetone or 164.83 ppm in DMSO.  Figure 2.4 13C APT NMR of monomer 2.5d in acetone-d6 (at 200 MHz)  Figure 2.5 13C APT NMR monomer 2.5d in DMSO-d6 (at 200 MHz) Differential scanning calorimetry (DSC) as seen in figure 2.6 was run on selected monomers. The results illustrated that there was a transition at 77 oC and at 143 oC for  40  monomer 2.5d with transitions for other monomers found in table 2.4. Further investigations into these transitions using polarized optical microscopy (POM) showed that a colour change was involved with a possible change in density of samples of the monomer at these temperatures as indicated by the formation of bubbles and movement thereof. The colour change was reversible and repeatable as well, going from yellow at low temperatures to brown at higher temperatures as may be seen in figure 2.7. This colour change, known as thermochromism,156 was found to cease after several cycles due to degradation of the monomer to a black colour. The observed thermochromism may be due to structural changes around the iron center via a change in the η6-arene ligand bonding187190  or weak charge transfer between the η6-arene ligand and the iron.103-106 Degradation may  be caused by a spin transition from low spin to high spin103-106,178-186 resulting in the iron center not being able to participate in bonding with the η6-arene ligand.88 Table 2.4 Thermal analysis of 2.5d, e, g, h Transition One (oC) 77 2.5d 68 2.5e 69 2.5g 54 2.5h  Transition Two (oC) 143 148 144 146  Figure 2.6 DSC thermogram of monomer 2.5d  41  (a)  (b)  (c)  (d)  (e)  (f)  (g)  (h)  (i)  (j)  Figure 2.7 Optical microscopy micrographs (bright field, 20x) of the thin film sections of 2.5d and 2.5g depending on the temperature. Pictures a-d correspond to monomer 2.5d whereas e-j correspond to monomer 2.5g. Pictures a and e were taken before heating at 23.3 ºC. b, c and f were taken on heating at 73.2, 140.3 and 105.2 ºC, respectively. Picture  42  g was taken after one minute at 105.2 ºC. d, h, i and j were taken on cooling at 77.0, 131.2, 121.6 and 36.3 ºC, respectively.  2.2.2 Synthesis and properties of cyclopentadienyliron containing polymers with an aliphatic spacer Condensation polymerization of the monomers with 1,8-octanedithiol (2.6) was accomplished using elevated temperature and small solvent volumes. The nucelophic aromatic substitution reaction between the aliphatic thiol and the chlorinated iron complex formed thio-ethers giving a polymer that contained ether, thio-ether and ester linkages as seen in scheme 2.2. Yields between 85-95% were obtained for the polymers with colours ranging between yellow and brown. Polymer analysis was conducted using TGA, DSC, 1H and  13  C NMR, IR and POM. Polymers 2.7b,f were prepared several times; each time  products were isolated in negligible yields. As a result the compounds were not analyzed. 2.5a-h  60o, 2 ml DMF, 8 hr  2.6= 1,8-octanedithiol M=Fe+PF6O  O O O  M  O x  M  S O  S 4 n  2.7a-h  Scheme 2.2 Upon polymerization of the metallated monomer with an aliphatic comonomer, the aliphatic region becomes more complex. This may be seen in figure 2.8 with data in table 2.5. The polymer based on 1,8-octanediol (2.7e) shows that there are four aliphatics present. The CH2 groups next to the ester and the thiol were found at 4.27 and 3.17 ppm  43  and the internal CH2 groups resonated at 1.36 and 1.71 ppm with significant overlap present between the two sets of aliphatics. The two sharp singlets between 2.5 ppm and 3.0 ppm along with the singlet around 8 ppm are characteristic of the polymerization solvent DMF. The cyclopentadienyl protons appeared as a singlet at 5.14 ppm and the complexed aromatics also collapsed to a singlet at 6.45 ppm. This is due to the similarity between a thio-ether and an ether linkage. The uncomplexed aromatics were found at 7.42 and 8.08 ppm as doublets with J coupling of 8.4 and 8.6 Hz. The strong resonance at 2.49 ppm correspondes to the residual DMSO in the deuterated solvent whereas the peak around 3.5 ppm is that of water in the solvent. Spinning side bands cause the appearance of a triplet like pattern for the singlets.  Figure 2.8 1H NMR spectrum of 2.7e in DMSO-d6 (at 200 MHz)  44  Table 2.5 1H NMR values, IR and yields for 2.7a,c-e,g,h in DMSO-d6 (200 MHz unless denoted by †, then at 300 MHz) Yield Aliphatics Cp Complexed Aromatics Carbonyl by (%) IR (cm-1) 1.33 (br s, 8H), 5.13 6.44 (s, 8H) 7.38 (s, 4H), 1719 2.7a† 90 1.62 (br s, 4H), (s, 8.08 (s, 4H) 3.16 (br s, 4H), 10H) 4.65 (br s, 4H) 95 1.30 (br s, 8H), 5.15 6.45 (s, 8H) 7.40 (s, 4H), 1715 2.7c 1.63 (br s, 4H), (s, 8.10 (s, 4H) 1.87 (br s, 4H), 10H) 3.17 (br s, 4H), 4.36 (br s, 4H) 1.30 (br s, 8H), 5.15 6.45 (s, 8H) 7.41 (s, 4H), 1717 2.7d 95 1.63 (br s, 8H), (s, 8.09 (s, 4H) 1.74 (br s, 4H), 10H) 3.17 (br s, 4H), 4.30 (br s, 4H) 93 1.36 (br s, 16H), 5.14 6.45 (s, 8H) 7.42 (d, J = 1716 2.7e 1.71 (br s, 18H), (s, 8.4Hz, 4H), 3.17 (br s, 4H), 10H) 8.08 (d, J = 4.27 (br s, 4H) 8.6 Hz, 4H) 1.29 (br s, 16H), 5.14 6.44 (s, 8H) 7.37 (s, 4H), 1716 2.7g† 85 1.67 (br s,12H), (s, 8.08 (s, 4H) 3.17 (br s, 4H), 10H) 4.26 (br s, 4) 1.25 (br s, 20H), 5.13 6.43 (s, 8H) 7.37 (s, 4H), 1716 2.7h† 93 1.66 (br s, 12H), (s, 8.05 (s, 4H) 3.16 (br s, 4H), 10H) 4.26 (br s, 4H) The 13C NMR spectrum of 2.7e may be found in figure 2.9, with data found in table 2.6. Upon forming the polymer, a noticeable difference in the complexed aromatics and the aliphatic regions may be seen. For the aliphatics, an overlap with the residual DMSO solvent was noted with only two of the expected four carbons appearing for the 1,8octanedithiol comonomer (2.6) appearing at 28.25 and 31.32 ppm. The remaining aliphatics from the metallated monomer appeared at 25.08, 27.82 and 64.57 ppm, with the remaining aliphatic carbon hidden by the solvent peak. The cyclopentadienyl carbons resonated at  45  78.50 ppm and complexed aromatic carbons next to the ether linkage were at 76.83 and 129.29 ppm. The complexed aromatic CH next to the thio-ether of the polymer appeared at 82.46 ppm and the quaternary carbon bonded to the sulphur was at 106.33 ppm. The uncomplexed aromatics and the carbonyl carbon were essentially unchanged upon polymer formation as expected. The aromatic CHs resonated at 119.86 and 131.55 ppm with the quaternary carbons at 126.91 and 157.14 ppm and the carbonyl carbon of the ester remaining at 164.00 ppm. The peaks at approximately 30, 35 and 163 ppm are due to the presence of DMF in the sample. Table 2.6 13C NMR shifts for 2.7a,c-e,g,h in DMSO-d6 (200 MHz unless †, then at 300 MHz)(* denotes quaternary carbons) Aliphatics Cp Complexed Aromatics Carbonyl 82.46, 119.70, 126.36*, 164.46 2.7a† 23.97, 27.71, 28.06, 78.41 76.95, 30.96, 62.70 106.34*, 129.11* 131.62, 157.35* 24.78, 27.89, 28.29, 78.59 76.96, 82.55, 119.96, 126.95*, 164.75 2.7c 31.35, 64.34 106.47*, 129.39* 131.73, 157.36* 82.67, 120.33, 127.09*, 164.83 2.7d 25.01, 27.98, 28.37, 78.68 77.15, 31.44, 64.71 106.53*, 129.48* 131.78, 157.39* 25.08, 27.82, 28.25, 78.50 76.83, 82.46, 119.86, 126.91*, 164.00 2.7e 31.32, 64.57 106.33*, 129.29* 131.55, 157.14* 82.32, 119.56, 126.54*, 164.21 2.7g† 24.78, 27.48, 27.89, 78.12 76.64, 31.05, 64.18 105.93*, 129.88* 131.20, 156.77* 82.60, 119.81, 126.23*, 164.62 2.7h† 25.13, 27.79, 27.85, 79.59 77.39, 28.16, 28.35, 28.65, 106.30*, 129.30* 132.17, 157.16* 31.33, 64.57  46  Figure 2.9 13C APT NMR spectrum of 2.7e in DMSO-d6 (at 200 MHz) The solubility of the polymers was tested in a variety of solvents. Overall, it was found that there was increased solubility in the more polar solvents such as DMF and DMSO and little to no solubility in the non-polar organic solvents such as chloroform. A summary of the data may be found in table 2.7. Table 2.7 Solubility data for 2.7a,c-e,g,h (S = soluble, PS = partially soluble, I = insoluble) DCM Acetone Acetonitrile DMF DMSO Chloroform THF PS S S S S I PS 2.7a PS S S S S I I 2.7c PS S S S S I PS 2.7d PS S S S S I I 2.7e PS S S S S PS PS 2.7g S S S S S I I 2.7h  The metallated polymers showed only a single transition in the DSC (table 2.8). This transition was found to decrease in temperature as the number of aliphatics increased. This has been noted for other polymers prepared and was also found for the monomers that were tested. The TGA showed that the metal was cleaved between 205-245 oC for each of  47  the metallated polymers and the backbone began to be degraded in all cases with the omission of 2.7c between 375-410 oC. In polymer 2.7c, the backbone did not begin to degrade until 510 oC. An example may be found in figure 2.10. Table 2.8 Thermal analyses of 2.7a,c-e,g,h Tg Weight Tonset Loss (%) (oC) 99 22 212 2.7a 87 23 218 2.7c 72 23 209 2.7d 70 24 208 2.7e 67 22 211 2.7g 65 21 209 2.7h  Tendset (oC) 243 230 239 236 234 235  Weight Loss (%) 36 45 28 39 52 48  Tonset (oC) 388 512 407 390 379 393  Tendset (oC) 454 593 440 460 454 456  Figure 2.10 TGA thermogram of 2.7d The inherent viscosities of selected metallated polymers were tested and compared to those of star-shaped molecules containing cyclopentadienyliron with known molecular weights (see chapter 3, section 3.2.5). Based upon this calibration, the degree of polymerization of the metallated polymers could be approximated and was found to be  48  within an expected range for polymers of this type.137,151,191-193 Molecular weights of the other polymers were found by GPC of the demetallated analogs. Table 2.9 Viscosity and molecular weight of 2.7c,e Inherent viscosity in DMSO molecular weight 0.236 36 100 2.7c 0.236 36 000 2.7e  n 29.6 28.1  2.2.3 Synthesis and properties of cyclopentadienyliron containing polymers with an aromatic spacer Condensation polymerization of the bimetallic monomer complexes was also accomplished using an aromatic dithiol monomer (2.8). This gave polymers with a larger percentage of the backbone being rigid in relation to the previously prepared polymers. These polymers were prepared in 86-97% yields with colours ranging between yellow and brown using the conditions shown in scheme 2.3. Analysis of the polymers was accomplished thermally via TGA and DSC and spectroscopically with 1H and 13C NMR as well as IR. 2.5a-h 60o, 2 ml DMF, 8 hr  O  O O O  M  2.8 = 4,4'-thiobisbenzenethiol M=Fe+PF6-  O x  M  S S  O  S n  2.9a-h  Scheme 2.3 Condensation polymerization of the monomers with aromatic sulphur was confirmed using 1H NMR. The data may be found in table 2.10 and as an example, polymer 49  2.9f may be found in figure 2.11. In this, it may be noted that broadening of the peaks has occurred which is reminiscent of polymerization. Trace amounts of the polymerization solvent DMF may be found as two singlets between 2.5 ppm and 3 ppm, water appeared around 3.75 ppm and residual DMSO in the deuterated solvent at 2.49 ppm. The aliphatics of the metallated monomer were found at 1.31, 1.68 and 4.26 ppm. The cyclopentadienyl protons resonated at 5.18 ppm with the complexed aromatics at 6.38 ppm as a broad doublet with coupling of 30 Hz. The uncomplexed aromatics were complicated by the addition of the sulphur containing comonomer. A multiplet containing the sulphur monomers’ aromatics and part of the metallated monomers’ aromatic was clearly visible between 7.40 and 7.60 ppm. The remaining aromatic of the metallated monomer was found at 8.06 ppm.  Figure 2.11 1H NMR spectrum of 2.9f in DMSO-d6 (at 300 MHz)  50  Table 2.10 1H NMR shifts, IR and yields for 2.9a-h in DMSO-d6 (at 300 MHz) Yield Aliphatics Cp Complexed Aromatics Carbonyl (%) Aromatics IR (cm-1) 4.06 (br s, 5.16 (s, 6.30 (br s, 4H) 7.40 (br s, 12H), 1717 2.9a 87 4H) 10H) 6.43 (br s, 4H) 8.05 (br s, 4H) 1.82 (s, 5.15 (s, 6.25 (br s, 4H), 7.38-7.60 (m, 1712 2.9b 89 2H), 4.30 10H) 6.43 (br s, 4H) 12H), 8.02 (s, (s, 4H) 4H) 1.74 (br s, 5.21 (s, 6.34 (br s, 4H), 7.41-7.59 (m, 1714 2.9c 94 4H), 4.30 10H) 6.40 (br s, 4H) 12H), 8.07 (br s, (br s, 4H) 4H) 1.45 (s, 5.20 (s, 6.31 (br s, 4H), 7.40-7.62 (m, 1710 2.9d 93 4H), 1.72 10H) 6.44 (br s, 4H) 12H), 8.06 (br s, (s, 4H), 4H) 4.29 (s, 4H) 1.36 (br s, 5.20 (s, 6.34 (s, 4H), 7.41 (s, 4H), 1714 2.9e 94 8H), 1.70 10H) 6.44 (s, 4H) 7.51 (s, 4H), (br s, 4H), 7.58 (s, 4H), 4.27 (br s, 8.06 (s, 4H) 4H) 1.31 (br s, 5.18 (s, 6.31 (s, 4H), 7.40-7.60 (m, 1712 2.9f 93 10H), 10H) 6.44 (s, 4H) 12H), 8.06 (s, 1.68 (s, 4H) 4H), 4.26 (s, 4H) 1.28 (br s, 5.19 (s, 6.34 (s, 4H), 7.40-7.58 (m, 1714 2.9g 96 12H), 10H) 6.44 (s, 4H) 12H), 8.06 (s, 1.68 (s, 4H) 4H), 4.26 (s, 4H) 1.26 (br s, 5.20 (s, 6.32 (s, 4H), 7.42 (br s, 4H), 1712 2.9h 97 16H), 10H) 6.45 (s, 4H) 7.48 (s, 4H), 1.69 (s, 7.59 (s, 4H), 4H), 4.27 8.06 (s, 4H) (s, 4H)  by  As shown in figure 2.12 with data in table 2.11, the 13C NMR data for the polymers corresponds closely to those of the monomers with the addition of the comonomer and helps to confirm the data of the 1H NMR. Using the example of polymer 2.9f, the aliphatic carbons appeared at 25.18, 27.92, 28.34, 28.60 and 64.64 ppm. The cyclopentadienyl  51  carbons resonated at 78.84 ppm. The complexed aromatics shifted slightly as expected upon losing the chloro-group and forming the thio-ether linkage. These appeared at 77.66 and 84.61 ppm for the complexed CH and at 103.72 and 130.13 ppm for the complexed quaternary carbons. The uncomplexed aromatic appeared at 120.08, 127.12 and 131.57 ppm for the aromatic CH and at 128.02, 136.13 and 157.00 ppm for the quaternary aromatics. The carbonyl carbon of the ester appeared at 164.65 ppm. Table 2.11 13C NMR shifts for 2.9a-h in DMSO-d6 (at 300 MHz)(* denotes carbons) Aliphatics Cp Complexed Aromatics 78.43 76.57, 84.08, 119.27, 125.93, 129.09*, 2.9a 62.14 103.13*, 131.06* 131.61, 138.05*, 156.50* 78.94 77.14, 86.26, 119.69, 127.00, 129.11*, 2.9b 28.82, 67.88 103.42*, 130.92* 131.34, 134.90*, 156.47* 78.41 77.31, 83.85, 119.70, 126.72, 128.38*, 2.9c 24.47, 63.99 103.47*, 130.00* 131.40, 135.63*, 157.20* 84.58, 119.85, 126.54, 128.33*, 2.9d 24.54, 27.53, 78.32 76.76, 63.33 103.61*, 130.21* 131.26, 135.73*, 156.61* 83.51, 119.74, 127.89, 128.48*, 2.9e 24.86, 27.63, 78.45 77.30, 28.04, 64.38 104.22*, 129.89* 131.38, 138.03*, 156.74* 84.61, 120.08, 127.12, 128.02*, 2.9f 25.18, 27.92, 78.84 77.66, 28.34, 28.60, 103.72*, 130.13* 131.57, 136.13*, 157.00* 64.64 83.77, 119.91, 127.07, 128.71*, 2.9g 25.10, 27.84, 79.10 78.65, 28.30, 28.55, 103.65*, 129.91* 131.56, 136.06*, 156.92* 64.55 85.10, 120.12, 128.30, 128.97*, 2.9h 25.32, 28.05, 78.84 77.35, 28.54, 28.84, 103.81*, 130.27* 131.75, 136.25*, 157.13* 64.75  quaternary Carbonyl 163.83 164.30 164.33 164.97 164.44 164.65  164.58  164.79  52  Figure 2.12 13C NMR spectrum of 2.9f in DMSO-d6 (at 300 MHz) Solubility of 2.9 over that of 2.7 was found to have in general decreased. This was expected as the flexible region of the polymer has been decreased via incorporation of the aromatic spacer 2.8. As per 2.7 the samples were more soluble in the polar organic solvents than they were in the non-polar organic solvents. Results are summarized in table 2.12. Table 2.12 Solubility data for polymers 2.9a-h (S = soluble, PS = partially soluble, I = insoluble) DMSO Chloroform THF DCM Acetone Acetonitrile DMF PS PS PS S S I PS 2.9a PS S S S S I PS 2.9b PS S S S S I PS 2.9c PS PS PS S S I PS 2.9d PS PS PS S S I PS 2.9e PS PS PS S S PS PS 2.9f PS PS PS S S I PS 2.9g PS PS PS S S I PS 2.9h  As shown in table 2.13, the thermal transitions decreased with increasing spacer length. An odd-even effect may also be noted and figure 2.13 shows polymer 2.9b. Most of these polymers also showed two transitions by DSC. The odd-even effect occurs when  53  those compounds with an aliphatic chain with an even number of carbons have higher glass transition temperatures than the odd numbered chains with one less or one more carbon.Tailing at the end of some DSC scans may be due to potential crystallization of the samples or to thermal degradation beginning below the temperature found by TGA. The TGA showed that the metal moiety was lost at temperatures above 200 oC as expected. The backbone was found to degrade above 350 oC with degradation being near complete at temperatures above 680 oC with polymer 2.9d shown in figure 2.14. Table 2.13 Thermal analysis of 2.9a-h T1 T2 Weight Loss (%) 109 157 16 2.9a 98 23 2.9b 106 161/185 20 2.9c  2.9d 2.9e 2.9f 2.9g 2.9h  74 97 81 98 83  149 136 115/141 124/144 124  16 18 22 12 18  Tonset (oC)  Tendset (oC)  215 214 219  239 243 250  204 217 211 211 218  241 238 243 235 235  Weight Loss (%) 62 49 17 50 34 48 36 50 42  Tonset (oC)  Tendset (oC)  488 544 405 578 349 348 385 380 378  597 683 493 666 430 500 474 516 481  Figure 2.13 DSC thermogram of 2.9b  54  Figure 2.14 TGA thermogram of 2.9d Table 2.14 shows the molecular weights calculated from the inherent viscosities as well as the degree of polymerization. These molecular weights and degrees of polymerization were similar to those obtained with the aliphatic spacer under the same conditions. Molecular weights of the remaining polymers were determined by GPC of the demetallated analogues. Discussion regarding these values may be found in chapter 3, section 3.2.5. Table 2.14 Viscosity and molecular weight of 2.9c,e Inherent viscosity in DMSO molecular weight 0.250 41 700 2.9c 0.274 51 100 2.9e  n 32.3 37.8  2.2.4 Synthesis and properties of demetallated polymers with an aliphatic spacer Organic analogues to the metallated polymers 2.7a-h were prepared via photolysis. The metallated polymers were irradiated with light in acetonitrile solution for 6-8 hours causing cleavage of the cylcopentadienyliron moiety (scheme 2.4). Yields of the organic polymers were highly variable ranging from 17-90%. Analysis of the demetallated polymers included 1H and  13  C NMR, IR spectroscopies as well as polarized optical  microscopy (POM), TGA and DSC. 55  2.7a-h  hv O  O O O  O x  S O  2.10a-h  S  8  n  Scheme 2.4 Demetallation of the metallated polymers may be confirmed via the loss of the cyclopentadienyl protons and complexed aromatics in the 1H NMR. Data relating to this may be found in table 2.15 and 2.10c is shown in figure 2.15. In this figure, it may be seen that the presence of the cyclopentadienyl protons and the complexed aromatic protons are lacking. The central aliphatics are still clearly present at 1.33, 1.62 and 1.92 ppm. The aliphatic CH2 next to the ester and thio-ether linkages are visible at 2.88 and 4.38 ppm. The aromatic region in the organic polymer shows several broad singlets at 6.99, 7.35 and 8.00 ppm corresponding to two sets of overlapping doublets. The sharp peak at 7.26 ppm is due to residual chloroform in the deuterated solvent whereas the peak around 3 ppm was due to water from polymer precipitation. A residual amount of acetone present in the NMR tube accounted for the peak at 2.04 ppm. The organic polymers were insufficiently soluble to have 13C NMR spectra run.  56  Table 2.15 1H NMR shifts and yields for 2.10a,c-e,g,h (samples run at 200 MHz in CCl3D unless †, then at 300 MHz in DMSO-d6) Yield (%) Aliphatics Aromatics Carbonyl by IR (cm-1) 0.96-2.33 (br m, 12H), 2.90 7.00-8.38 (br m, 16H) 1717 2.10a† 90 (br s, 4H), 4.40 (br s, 4H) 73 1.33 (br s, 8H), 1.62 (br s, 6.99 (br s, 8H), 7.35 1714 2.10c 4H), 1.92 (br s, 4H), 2.88 (br s, 4H), 8.00 (br s, (br s, 4H), 4.38 (br s, 4H) 4H) 1.27 (br s, 8H), 1.41(s, 7.01 (br s, 8H), 7.34 1713 2.10d† 17 4H), 1.52 (br s, 4H), 1.68 (br s, 4H), 7.92 (br s, (br s, 4H), 2.90 (br s, 4H), 4H) 4.23 (br s, 4H) 21 1.40 (br s, 12H), 1.75 (br s, 7.00 (br s, 8H), 7.12 1716 2.10e 12H), 2.89 (br s, 4H), 4.29 (br s, 4H), 8.01 (br s, (br s, 4H) 4H) 1.40 (br s, 20H), 1.60 (br s, 7.05 (br s, 8H), 7.35 1718 2.10g† 39 8H), 2.88 (br s, 4H), 4.36 (br s, 4H), 8.06 (br s, (br s, 4H) 4H) 1.42 (br s, 32H), 2.75 (br s, 7.14 (br s, 8H), 7.31 1715 2.10h† 75 4H), 4.28 (br s, 4H) (br s, 4H), 8.07 (br s, 4H)  Figure 2.15 1H NMR spectrum for 2.10c in chloroform-d (at 200 MHz) When the solubilities of the organic polymers are compared to those of the metallated anologues, a reversal in the relative solubilities was noted, that is, the organic polymers displayed increased solubility in the non-polar organic solvents and decreased solubility in the polar solvents. This may be seen in table 2.16.  57  Table 2.16 Solubility data for 2.10a,c-e,g,h insoluble) DCM Acetone Acetonitrile S PS PS 2.10a S I I 2.10c S I I 2.10d S PS PS 2.10e S PS I 2.10g S PS I 2.10h  (S = soluble, PS = partially soluble, I = DMF PS PS PS PS S S  DMSO PS I I I PS PS  Chloroform S S S S S S  THF PS I I I S S  TGA shows that although the polymers are demetallated, there appears to be degradation of the polymeric backbone in the region that the metal was cleaved in the metallated polymers as seen for polymer 2.10d in figure 2.16. This loss, occurring from 150 oC to 255 oC may be due breakdown of the ester linkage as opposed to the ether/thioether linkages as seen in table 2.17. Further backbone breakdown corresponding the ether/thioether linkages or the loss of the cyclopentadienyliron moiety was noted above 380 oC to 450 oC. The temperature at which thermal transitions were found to occur was, like the monomers and metallated polymers, found to decrease with increasing length of the aliphatic chain. Compound 2.10a may be seen in figure 2.17.  Figure 2.16 TGA thermogram of 2.10d  58  Table 2.17 Thermal analysis for 2.10a,c-e,g,h (DSC from run c, TGA to 500 oC only) T1 T2 Weight Tonset Tendset Weight Tonset Tendset Loss Loss (%) (%) 157 20 205 253 36 399 441 2.10a 165 8 150 219 62 388 447 2.10c 153 4 188 223 65 388 434 2.10d 75 130 4 189 232 66 385 439 2.10e 58 10 221 242 61 384 448 2.10g 116 9 213 239 63 390 446 2.10h  Figure 2.17 DSC thermogram of 2.10a The molecular weight data corresponding to the demetallated polymers may be found in table 2.18. In this, it may be noted that the degrees of polymerization and the equivalent weights of the metallated polymers via extrapolation from the demetallated weights are strikingly different than those gathered from the viscosity data of the metallated polymers (table 2.9). Based upon the GPC data, small polymers were formed. Possible reasons for the difference between the two sets of molecular weight data would be the standards used to calibrate the instrumentation. It is also possible that there was some breakdown of the polymers at the ester bond during the demetallation process and a decreased solubility of the polymer during the extraction and washing process resulting in 59  loss of the higher molecular weight fraction. For more discussion of these values, see chapter 3, section 3.2.5. The polydispersity index (PDI) illustrated that most of the polymers displayed a narrow range of weights. Compound 2.10e however did not. Upon comparison of these values to polymers of similar composition prepared from solely organic precursors showed a decrease in both the Mn and Mw but little change in the PDI.9 Table 2.18 Molecular weights for 2.10a,c-e,g,h in THF (where metallated refers to the molecular weight of the polymer if the metal was present based upon the demetallated polymers molecular weight) Mn Mw PDI metallated n 2 600 3 500 1.39 6 300 5.3 2.10a 4 000 6 200 1.56 11 000 9.0 2.10c 5 200 6 700 1.28 11 600 9.3 2.10d 5 000 11 200 2.25 19 100 15 2.10e 4 500 6 900 1.52 11 600 8.9 2.10g 5 700 8 200 1.44 13 600 10.2 2.10h  2.2.5 Synthesis and properties of demetallated polymers with an aromatic spacer Organic polymers (2.11a-h) with a predominately rigid backbone containing ether, thio-ether and ester linkages were prepared via the photolysis of the metallated polymers (2.9a-h). This was accomplished in 35-88% yields and shown in scheme 2.5. Analysis of the demetallated polymers included spectroscopic (1H and 13C NMR, IR and POM) as well as thermal (TGA and DSC).  60  2.9a-h hv O  O O O  O x  S S  O  S n  2.11a-h  Scheme 2.5 As with the organic aliphatic comonomer polymers (2.10a-h), the loss of the cyclopentadienyl protons and the complexed aromatic are indicative of the demetallation reaction having been successful. Using the example of 2.11g (figure 2.18 with data in table 2.19), the aliphatic CH2 were found at 1.30, 1.73 and 4.23 ppm as expected based upon the metallated polymer and the monomer values. The aromatic region contains two sets of doublets at 6.98 and 7.28 ppm for the aromatic CH between the sulphur and oxygen and 7.46 and 8.03 ppm for the aromatic CH with the ether and ester linkage. An overlapping singlet at 7.28 ppm corresponded to the comonomer thiobisbenzenethiol. Due to low solubility of the organic polymers, the 13C NMR was not possible.  61  Table 2.19 1H NMR shifts, IR and yields for 2.11a-h in DMSO-d6 (samples run at 300 MHz) Yield Aliphatics Aromatics Carbonyl by (%) IR (cm-1) 4.58 (br s, 4H) 7.10 (br s, 8H), 7.25 (br s, 1721 2.11a 77 8H), 7.42 (br s, 4H), 7.96 (br s, 4H) 1.74 (br s, 2H), 4.45 (br 7.04 (s, 8H), 7.23 (s, 12H), 1715 2.11b 51 s, 4H) 7.40 (s, 4H), 8.00 (s, 4H) 1.82 (br s, 4H), 4.29 (br 7.28 (br s, 16H), 7.45 (br s, 1713 2.11c 72 s, 4H) 4H), 7.98 (br s, 4H) 1.45 (br s, 4H), 1.71 (br 7.09 (br s, 8H), 7.29 (br s, 1711 2.11d 36 s, 4H), 4.24 (br s, 4H) 8H), 7.44 (br s, 4H), 7.96 (br s, 4H) 1.33 (br s, 8H), 1.66 (br 7.23 (br s, 8H), 7.41 (br s, 1713 2.11e 67 s, 4H), 4.23 (br s, 4H) 12H), 7.95 (br s, 4H) 1.39 (br s, 10H), 1.67 (br 7.13 (br s, 20H), 8.04 (br s, 1714 2.11f 44 s, 4H), 4.25 (br s, 4H) 4H) 1.30 (br s, 12H), 1.73 (br 6.98 (s, 8H), 7.28 (s, 12H), 1713 2.11g 88 s, 4H), 4.23 (br s, 4H) 7.46 (s, 4H), 8.03 (s, 4H) 1.29 (br s, 16H), 1.72 (br 6.97 (s, 8H), 7.20 (s, 12H), 1712 2.11h 72 s, 4H), 4.30 (br s, 4H) 7.40 (s, 4H), 8.01 (s, 4H)  Figure 2.18 1H NMR spectrum for 2.11g in DMSO-d6 (at 300 MHz) As seen in table 2.20, the solubilities of the demetallated polymers containing aromatic spacers (2.11) was less than that of both the analogous metallated polymers (2.9) and similar demetallated polymers with aliphatic spacers (2.10).  62  Table 2.20 Solubility data for 2.11a-h (S = soluble, PS = partially soluble, I = insoluble)  2.11a 2.11b 2.11c 2.11d 2.11e 2.11f 2.11g 2.11h  DCM S PS PS PS S PS S S  Acetone I I I PS PS PS I I  Acetonitrile I I I I I PS I I  DMF S I PS S PS PS PS S  DMSO S I PS S PS I PS PS  Chloroform S S S PS S S S S  THF S I S S PS PS S S  As seen with the aliphatic organic polymers, there was a breakdown of the polymer backbone in the region normally associated with that of the iron moiety (figure 2.19). This may be related to the ester linkage and was also seen in polymers 2.10. The ether/thioether degradation was found to occur above 315 oC to 550 oC. The DSC data illustrated again the odd-even effect as well as an increase in the number of aliphatics in the backbone decreased the temperature at which the thermal transitions were noted (table 2.21). As seen in figure 2.20 of compound 2.11b, a glass transition appears as the second order phase transition around 58 oC, the exothermic peak corresponds to crystallization at 120 oC and the endothermic peaks to melting of the sample between 154-174 oC. Table 2.21 Thermal analysis for 2.11a-h T1 T2 Weight Loss (%) 92 6 2.11a 58/120 154/174 11 2.11b  2.11c 2.11d 2.11e 2.11f 2.11g  64 71/132 61 52/157 40  159/186 137/163 174/190 167/184 153/186  4 28 3 7 9  2.11h  49  141/169 7  Tonset (oC)  Tendset (oC)  208 245  243 348  198 87 206 178 208  227 133 241 215 232  216  239  Weight Loss (%) 26 32 21 41 10 13 52 8 48 38  Tonset (oC)  Tendset (oC)  429 387 518 365 319 380 393 364 405 386  547 473 550 501 382 441 488 387 480 451  63  Figure 2.19 TGA thermogram of 2.11d  Figure 2.20 DSC thermogram of 2.11b The molecular weight data determined from the demetallated, organic polymers are presented in table 2.22. The PDI for these polymers were comparable to polymers 2.10 although they had decreased Mn and Mw. Based upon this data, oligomers were formed and end group analysis from the NMR data should be possible. Since the GPC data conflicts with the NMR as well as the viscosity measurements of the metallated polymer several things may be concluded. First, that the linear polystyrene standards used in preparation of the calibration illustrate a poor calibration choice. Second, that the samples displayed poor solubility in the extraction solvent, thus the polymeric fraction of the sample with high  64  molecular weights were not soluble and hence not analyzed. Finally, that the samples may have become subject to hydrolysis of the ester linkage during the demetallation process. For more discussion of this, see section 3.2.5 in chapter 3. Table 2.22 Molecular weights of 2.11a-h in THF Mn Mw PDI 1 300 1 900 1.39 2.11a 1 100 1 500 1.27 2.11b 1 800 2 600 1.44 2.11c 1 200 1 600 1.32 2.11d 2 500 3 300 1.32 2.11e 3 100 4 600 1.47 2.11f 3 700 5 500 1.49 2.11g 3 400 4 700 1.36 2.11h  metallated 3 300 2 600 4 400 2 700 5 400 7 500 8 900 7 500  n 2.6 2.0 3.4 2.0 4.0 5.5 6.5 5.4  2.3 Conclusions Thermochromic monomers were prepared using facile methods. The monomers contained aliphatic chains of various lengths that were bonded via ester linkages to aromatic carboxylic acid ether substituted η6-arene-η5-cyclopentadienyliron complexes to give a bimetallic compound. The properties of these were tested and found to display interesting thermal properties, namely thermochromism. The monomers were then polymerized to give thiol bridged polymers. Thermal properties were analyzed and found to display standard thermal degradation above 205 oC corresponding to the loss of the metal moiety with backbone breakdown occurring above 350  o  C. Several thermal  transitions were noted in the metallated polymers. Upon demetallation, the polymers were found to begin their breakdown at lower temperatures than the metallated polymers, due possibility to the presence of the ester linkage. Breakdown of the remains of the polymeric backbone occurred above 320 oC. Several thermal transitions prior to degradation of the  65  polymer were also noted. These corresponded to glass transitions, melting and crystallizations.  2.4 Experimental 2.4.1 Characterization 1  H and  13  C NMR spectra were collected using a Gemini 200 NMR spectrometer  (200 and 50 MHz, respectively) and a Bruker Avance DXP300 (300 MHz and 75 MHz, respectively). Solvent residues were used for reference and reported values were collected on a Gemini 200 NMR unless otherwise stated. Chemical shifts were calculated in ppm and J couplings were calculated in hertz (Hz). Differential scanning calorimetry (DSC) was done using a Mettler 821e with a heating rate of 20 oC/min under a flow of nitrogen or using a Pyris Diamond DSC with Intracooler (Perkin Elmer) with a heating/cooling rate of 10 oC/min. Polarized optical microscopy (POM) was performed using an Olympus BX51-P polarizing microscope in conjunction with a Linkam LS350 heating/cooling stage. Thermogravimetric analysis (TGA) was accomplished using a Mettler TGA/SDTA851e with a heating rate of 20 oC/min under a flow of nitrogen. Viscosity measurements were made using a Brookfield Model DV II + Viscometer at 100 RPM, with a UL adapter set to 25 oC in dimethylsulphoxide (DMSO). Molecular weights were estimated from the inherent viscosity as calibrated based upon star-shaped molecules. A Rayonet photoreactor was used for photolytic demetallation with 8 watt bulbs centered at 300 nm. Gel Permeation Chromatography (GPC) was accomplished using a Waters 1525 binary HPLC pump and Waters 2410 refractive index detector using THF as eluent. Molecular weights were relative to calibration by polystyrene standards. Solubility testing was accomplished visually in a glass vial using a spatula tip of the compound in approximately 1 mL of  66  solvent. The solution was mixed via pipette and allowed to sit for approximately 3 min before observation occurred. Samples were then lightly heated and re-observed upon cooling.  2.4.2 Materials Complexes 2.1 and 2.3 were prepared according to previously established methodologies.121 Compounds 2.2, 2.4a-h, 2.6 and 2.7 as well as dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP) were purchased from Aldrich and used as received. All solvents were HPLC grade and were used without purification with the omission of tetrahydrofuran (THF) which was purified using a method adapted from literature.194  2.4.3 Procedures 2.4.3.1 Synthesis of 2.3 In a 100 mL round bottom flask fitted with a condenser and stir bar, 4 mmol of the iron complex (2.1), 16 mmol of the 4-hydroxybenzoic acid (2.2), 40 mmol of potassium carbonate and 25 mL each of DMF and THF were heated to 55-60 oC for 16 hours with stirring, under nitrogen and covered from light. The viscous salmon pink product was poured into 10% HCl and NH4PF6 was added. The product was separated from unreacted carboxylic acid via extraction into DCM followed by brief washings with distilled water. The organic layer was dried with MgSO4, filtered and evaporated. The residue was dissolved in acetone and precipitated into ether. The solid product was filtered and left to dry, covered from light under reduced pressure.  67  2.4.3.2 Synthesis of 2.5a-h A slight excess of the acid complex (2.3, 1.2 mmol) was mixed with the appropriate diol (2.4a-h, 0.5 mmol), DCC (1.3 mmol) and DMAP (1.3 mmol) with DCM (5 mL) and DMSO (2 mL) as the solvents in a 50 mL round bottom flask under nitrogen, covered from light with stirring for 16 hours. The reaction was stopped by pouring into approximatly 125 mL 10% HCl with stiochiometric NH4PF6. The product was then promptly extracted into DCM and washed with water. The organic layer was dried with MgSO4, filtered and the solvent evaporated. The residue was dissolved in acetone, filtered and loaded onto a neutral activated alumina column. Elution of the product was accomplished via acetone as the first yellow band. The product solution was concentrated and precipitated into 10% HCl with NH4PF6 and quickly filtered. The solid was allowed to dry under reduced pressure in the dark.  2.4.3.3 Synthesis of 2.7a,c-e,g,h and 2.9a-h A reaction mixture consisting of 0.5 mmol in comonomer set (2.5a-h and 2.6 or  2.8), 2.0 mmol of dried potassium carbonate and 2 mL of DMF was heated to 60 oC for 8 hours under nitrogen atmosphere and covered from light. The mixture was then poured into 10% HCl with NH4PF6 and the product precipitated. The solid was filtered and allowed to dry covered under reduced pressure.  2.4.3.4 Synthesis of 2.10a,c-e,g,h and 2.11a-h The metallated polymer (2.7 or 2.9, 0.500 g) was dissolved in a mixture of DCM and DMSO (40 mL total, ratio dependant on solubility) in a 50 mL glass Pyrex tube. Photolysis, after degassing with nitrogen, was carried out for 8 hours in a rayonette photoreactor. The organic polymer was isolated by evaporation of the DCM followed by  68  extraction with chloroform containing sufficient nitromethane for solubility. The organic layer was washed, dried with magnesium sulphate, filtered and evaporated. The remaining residue was dissolved into chloroform and precipitated with diethyl ether. The solid was filtered and dried under reduced pressure.  69  3 Linear and singly branched star-shaped molecules containing cyclopentadienyliron moieties 3.1 Introduction The majority of star-shaped molecules are organic in nature, with the most common being star-polymers.195-202 Organic star-shaped molecules prepared by step-wise synthesis tend to show interesting properties such as liquid crystallinity203 or light emission.204 Some star-polymers contain metals at the centre for the purpose of polymerization catalysts,205-223 while others contain metals at the periphery.224-225 Examples of star-shaped molecules in which a metal may be found to be present throughout the star-arm are rare.133,226-228 The field of dendrimers or branched stars is a popular area of research with many metallated examples to be found as well as multiple review articles having been published.29-48,229-244 Examples of ferrocene and η6-arene-η5-cyclopentadienyliron containing dendrimers and star-shaped molecules may be found in the literature.38,39,43-46,133,224-227,231-233,245 These metallated branched macromolecules have shown via cyclic voltametry that each of the iron centers act independently and are not influenced by iron atoms on the other arms unless significant conjugation is present in the molecule. The electron transfer has also been found to be reversible at low temperatures and some of the compounds have shown potential to act as molecular batteries. 38,39,43-46,133,224-227,231-233,245 Properties such as thermal degradation and glass transition temperatures have not been as well studied. In this thesis, star-shaped molecules were prepared using predominately nucleophilic aromatic substitution. Various di- and tri-phenolic groups were used, as were carboxylic acids for the formation of ester linkages. The effects of adding well defined branch points into the polymers were studied using spectroscopy and thermal analysis.  70  Comparison to other known polymers containing cyclopentadienyliron moieties alternating along the polymeric backbone will be presented. Differences between similar ether and ester containing star-shaped molecules will be highlighted. Spectroscopic analysis was conducted using 1H and 13C NMR spectroscopy and thermal analysis by TGA and DSC.  3.2 Results and discussion 3.2.1 Synthesis and properties of allyl-capped star-shaped molecules Star-shaped molecules with ether linkages were prepared to contain up to 15 cyclopentadienyliron moieties. This was achieved via a combination of convergent and divergent syntheses. Divergent synthesis was used to prepare a previously reported trimetallic core.133 Linear chains containing between one to four metallic units were then prepared according to scheme 3.1 using nucleophilic aromatic substitution. Yields of the linear chains were between 70-97% and the colours ranged from pale yellow for the free chloro-chains to dark brown for the phenolic chains.  71  OH 2.1 3.1 K2CO3 O  M=Fe+PF6-Cp  M Cl  3.2  OH  K2CO3, 3.3 = HO O  OH M O 3.4 2.1, K2CO3  O  O M  M O  Cl  3.5 3.3, K2CO3  O  OH 2  M O 3.6 2.1, K2CO3 O  O 2  M  M  O  Cl 3.7  3.3, K2CO3 O  OH 3  M 3.8  O  2.1, K2CO3 O  O 3  M O 3.9  M Cl  Scheme 3.1  72  1  H and  13  C NMR spectroscopy were used to confirm that nucleophilic aromatic  substitution had taken place. Figure 3.1 shows the 1H NMR spectrum of compound 3.2. This clearly shows the cyclopentadienyl resonance at 5.36 ppm. The protons on the complexed aromatic groups appeared as two singlets at 6.40 and 6.76 ppm. The aromatics from the 2-allylphenol appeared as a broad doublet centered around 7.35 ppm. The methylene group was visible as a doublet at 3.33 ppm with coupling of 5.9 Hz, the allylic methylene as a multiplet between 4.94 and 5.03 ppm and the CH also as a multiplet between 5.84 and 5.92 ppm. Residual acetone solvent is visible at 2.04 ppm. A summary of the proton shifts and the percent yields for the allyl-capped chains are given in table 3.1.  Figure 3.1 1H NMR spectrum of 3.2 in acetone-d6 (at 200 MHz)  73  Table 3.1 1H NMR values and yields for 3.2, 3.4-3.9 (in DMSO-d6 omitting 3.2 and 3.5 in acetone-d6) Yield Aliphatics Cp Complexed Aromatics OH (%) Aromatics 3.33 (d, J=5.9Hz, 2H, 5.36 (s, 5H) 6.40 (s, 2H), 7.35 (br d, 3.2 89 CH2), 4.94-5.03 (m, 6.76 (s, 2H) J=12.9 Hz, 2H, CH2), 5.84-5.92 4H) (m, 1H, CH) 3.28 (s, 2H, CH2), 5.19 (s, 5H) 6.17 (d, J=4.3 6.89 (d, J=8.6 9.71 3.4 88 Hz, 4H) Hz, 2H), 7.13- (s, 1H) 4.96-5.07 (m, 2H, 7.36 (m, 6H) CH2), 5.87-6.03 (m, 1H, CH) 3.39 (d, J=4.0Hz, 2H, 5.31 (s, 5H), 6.31 (d, J=7.0 7.28-7.44 (m, 3.5 71 CH2), 4.98-5.09 (m, 5.37 (s, 5H) Hz, 2H), 6.45 4H), 7.56 (s, 2H, CH2), 5.90-6.03 (d, J=6.6 Hz, 4H) (m, 1H, CH) 2H), 6.54 (d, J=6.6 Hz, 2H), 6.76 (d, J=6.6 Hz, 2H) 3.32 (s, 2H, CH2), 5.22 (s, 5H), 6.14-6.35 (m, 6.90 (d, J=8.6 9.74 3.6 93 Hz, 2H), 7.15 (s, 1H) 4.94-5.08 (m, 2H, 5.25 (s, 5H) 8H) (d, J=9.0 Hz, CH2), 5.85-5.98 (m, 1H, CH) 2H), 7.237.37 (m, 4H), 7.47 (s, 4H) 3.33 (s, 2H, CH2), 5.26 (s, 5H), 6.24-6.49 (m, 7.23-7.49 (m, 3.7 94 4.96-5.08 (m, 2H, 5.28 (s, 5H), 10H), 6.83 (d, 4H), 7.57 (s, CH2), 5.80-6.00 (m, 5.30 (s, 5H) J=6.6 Hz, 2H) 8H) 1H, CH) 3.30 (s, 2H, CH2), 5.24 (br s, 6.13-6.35 (m, 6.92 (br s, 9.80 3.8 97 5.03 (br s, 2H, CH2), 15H) 12H) 2H), 7.12- (s, 1H) 5.90 (br s, 1H, CH) 7.48 (m, 14H) 3.31 (d, J=5.9 Hz, 5.22 (s, 5H), 6.25 (d, J=5.5 7.10-7.56 (m, 3.9 97 2H, CH2), 4.95-5.08 5.26 (s, 5H), Hz, 2H), 6.40 16H) (m, 2H, CH2), 5.80- 5.28 (br s, (br s, 14H) 6.00 (m, 1H, CH) 10H) The 13C NMR confirms the 1H NMR. Figure 3.2 shows the 13C NMR of compound  3.2.  13  C NMR analysis for all of the allyl-capped chains is given in table 3.2. In the  13  C  NMR, the cyclopentadienyl carbons were seen at 80.27 ppm. The complexed aromatics appeared at 76.97 and 87.60 ppm for the complexed Ar-CH and 104.70 and 116.95 ppm for  74  the quaternary complexed aromatics. The quaternary carbons of the uncomplexed aromatics appeared at 133.49 and 151.96 ppm whereas the Ar-CH were present at 121.02, 127.51, 129.35 and 132.26 ppm. Finally, the aliphatic carbons resonated at 34.11, 116.95 and 126.38 ppm. The acetone solvent residue appears as two peaks at 29.9 and 206.7 ppm.  Figure 3.2 13C APT NMR of 3.2 in acetone-d6 (at 200 MHz)  75  Table 3.2 13C NMR values for 3.2, 3.4-3.9 (* designates quaternary C, at 200 MHz)(in DMSO-d6 omitting 3.2 and 3.5 in acetone-d6) CH2 CH Cp Complexed Aromatics Aromatics 76.97, 87.60, 121.02, 127.51, 129.35, 132.26, 3.2 34.11, 136.38 80.27 116.95 104.70*, 116.95* 133.49*, 151.96* 74.76, 75.97, 117.71, 120.72, 122.84, 127.13, 3.4 34.34, 136.78 78.66 116.89 116.89*, 131.26* 129.29, 132.25, 132.90*, 146.40*, 152.91*, 156.52* 76.15, 120.78, 124.22, 124.30, 127.28, 3.5 34.44, 136.75 79.04, 75.81, 116.95 80.50 77.02, 87.78, 129.33, 132.37, 134.03*, 151.57*, 104.95*, 116.95*, 151.42*, 153.05* 131.69*, 132.01* 74.97, 116.80, 120.08, 122.03, 122.75, 3.6 33.36, 135.89 77.66, 73.57, 116.66 77.91 116.66*,129.76*, 126.35, 128.53, 131.36, 131.61*, 130.10*, 130.16*, 144.70*, 150.93*, 151.08*, 151.66*, 131.13* 155.76* 73.42, 74.75, 116.66, 119.91, 121.78, 122.73, 3.8 33.17, 135.73 77.77 116.48 77.52, 116.48*, 126.13, 128.35, 130.93*, 131.19, 129.72*, 129.92*, 131.39*, 144.51*, 150.76*, 151.47*, 130.16* 155.60* 76.01, 119.95, 122.78, 123.05, 126.23, 3.7 33.21, 135.79 77.81, 74.82, 116.56 79.24 86.57, 103.53*, 128.41, 130.02*, 130.11*, 130.23*, 116.56*, 132.05* 131.00*, 131.25, 150.25*, 150.82*, 151.13*, 151.56* 33.32, 135.89 77.95 73.62, 74.94, 116.84, 120.04, 121.94, 123.00, 3.9 116.57 76.14, 77.68, 126.32, 128.53, 130.08*, 130.37*, 79.41, 86.70, 131.06*, 131.35, 144.66*, 150.25*, 103.58*, 116.67*, 150.25, 150.85*, 151.19*, 151.65*, 131.51*, 132.19* 155.74*  These allyl-capped chains (3.2, 3.4-3.9) were then reacted with tri-metallic cores as seen in scheme 3.2 to give star-shaped molecules containing 3, 6, 9, 12 or 15 irons. The trimetallic allyl-capped molecule was prepared in a similar manner using 2-allylphenol and the central chloro-based core. Tri-metallic cores 3.10 and 3.11 had been previously published by the Abd-El-Aziz research group.133 These reactions occurred under mild conditions in the presence of potassium carbonate in DMF. Yields were between 55-97%. The large yield range illustrates the problem of product loss during column purification of  76  the tri-substituted (desired) product from that of the mono- and di-substituted (incomplete reaction) products. The amount of tri-substituted product to the incomplete reaction products was high and the impurities were noted via the presence of a broad phenolic proton peak above 10 ppm in the 1H NMR spectrum of the crude products. Cl  3.2 3.5 3.7 3.9  M O  3.10 O  HO  M  O  Cl  M  O  Cl M  O  O  3.1  M  3.11  O O  K2CO3  M  DMF  OH O  OH  K2CO3  O  DMF  M O  O  M  O n  O n  M  O  O  M O M  O n O  O  3.12, 3.13, 3.14, 3.15, 3.16,  n n n n n  = = = = =  0 1 2 3 4  M=Fe+PF6-Cp  M O  Scheme 3.2  77  The formation of the star-shaped molecule from the allyl-capped arm and the previously prepared three armed core could be confirmed using 1H and  13  C NMR. The  indicative changes may be seen in figure 3.3 with compound 3.13. In this, the tri-metallic core contributes to the cyclopentadienyl resonance at 5.23 ppm. The complexed aromatics now contain two sets of doublets at 6.22 and 6.34, 6.38 and 6.57 ppm. One set of doublets comes from the core and the other set from the allyl-capped chain. The singlet at 7.52 ppm corresponds to the 12 protons of the aromatic in the star-shaped molecules chain. The remaining 18 protons seen as a multiplet between 7.23 ppm and 7.45 ppm are those from the central core and the allyl-cap aromatic. The aliphatics present in the star-shaped molecule appear in the same general location as for the allyl-capped chain, namely at 3.34, between 4.95-5.08 and 5.85-6.10 ppm. The singlets found between 2.5 and 3 ppm as well as at 8 ppm correspond to the reaction solvent DMF. Residual DMSO in the deuterated solvent appeared at 2.49 ppm. Spinning side bands may also be seen in figure 3.3. Complete 1H NMR analysis is given in table 3.3.  Figure 3.3 1H NMR spectrum of 3.13 in DMSO-d6 (at 200 MHz)  78  Table 3.3 1H NMR values for 3.12-3.16 (3.12 in acetone-d6, rest in DMSO-d6) Aliphatics Aromatics Complexed Ar. Cp 3.12 3.34 (d, J=6.3, 6 H), 7.22-7.38 (m, 18 H) 6.33 (d, J=7.0, 6 H), 5.33 (s, 15 H) 4.94-5.04 (m, 6 H), 6.61 (d, J=6.3, 6 H) 5.85-5.94 (m, 3 H) 3.13 3.34 (s, 6 H), 4.95- 7.23-7.45 (m, 18 6.22 (d, J=7.0, 6 H), 5.23 (s, 30 H) 5.08 (m, 6 H), 5.85- H), 7.52 (s, 12 H) 6.34 (d, J=7.8, 6 H), 6.10 (m, 3 H) 6.38 (d, J=7.4, 6 H), 6.57 (d, J=6.6, 6 H) 3.14 3.31 (d, J=6.3, 6 H), 7.23-7.38 (m, 18 6.25(d, J= 6.6, 6 H), 5.25 (s, 45 H) 4.97-5.09 (m, 6 H), H), 7.49 (s, 24 H) 6.35 (s, 12 H), 6.48 5.81-6.00 (m, 3 H) (d, J= 6.3, 6 H), 6.55 (d, J = 8.0, 6 H), 6.81 (d, J = 7.2, 6 H) 5.28 (s, 60 H) 3.15 3.33 (s, 6 H), 5.09(m, 7.41-7.47 (m, 18 6.20-6.65 (m, 48 H) 6 H), 6.00 (m, 3 H) H), 7.45 (s, 36 H) 5.28 (br s, 75 3.16 3.32 (br s, 6 H), 7.13-7.54 (m, 63 H) 6.37-6.23 (m, 60 H) 5.06(br s, 6 H), 5.80H) 6.10(br m, 3 H) 13  C NMR was also used in the analysis of the allyl-capped star-shaped molecules.  Using 3.13 as an example, the presence of two cyclopentadienyl groups at 77.94 and 78.09 ppm may be distinguished as was expected based upon the structure but not visible in the 1  H NMR at 200 MHz. The corresponding complexed aromatics appeared at 76.01 and  75.01 ppm with the quaternary complexed aromatics at 129.19 and 131.16 ppm. Once again, the aliphatics have shown little shift upon formation of the star-shaped molecule from the chain, with values of 33.37, 116.62 and 135.92 ppm. Finally, the aromatic resonances from the chain appeared at 120.07, 128.59, 130.70 131.44 ppm and the quaternary aromatics at 130.20 and 151.73 ppm. The remaining aromatics from the core appeared at 109.95, 120.07, 122.88 ppm, with quaternary carbons at 150.87, 151.01 and 156.49 ppm. The strong resonance at 39.5 ppm corresponded to residual DMSO in the deuterated solvent. Complete  13  C NMR data for the allyl-capped star-shaped molecules  may be seen in table 3.4.  79  Figure 3.4 13C APT NMR of 3.13 in DMSO-d6 (at 200 MHz) Table 3.4 13C NMR values for 3.12-3.16 (3.12 in acetone-d6, rest in DMSO-d6) Aliphatics Aromatics Complexed Ar. 111.46, 120.31, 120.51, 126.90, 76.06, 76.40, 116.82*, 3.12 34.12, 132.12, 129.18, 136.64, 131.62*, 130.94* 131.94 152.94*, 157.36* 109.95, 120.07, 122.88, 128.59, 76.01, 75.01, 129.19*, 3.13 33.37, 130.20*, 130.70, 131.44, 131.16* 116.62, 150.87*, 151.01*, 151.73*, 135.92 156.49* 109.69, 119.27, 120.03, 121.96, 74.94, 76.12, 79.30, 3.14 33.30, 116.64, 122.81, 126.32, 128.50, 130.04*, 86.65, 103.64*, 135.87 130.14*, 130.62*, 131.10*, 132.10* 131.34, 135.87, 150.33*, 150.94*, 151.66*, 155.74* 33.23, 110.25, 119.97, 120.60, 121.85, 74.84, 116.59*, 3.15 116.59, 122.83, 126.22, 128,41, 129.13*, 131.80* 135.79 129.79, 130.06*, 130.17*, 130.98*, 131.80, 150.81*, 151.54*, 155.63*, 156.40* 116.52*, 116.61*, 116.76, 86.35, 79.30, 76.61, 3.16 33.26, 115.96, 119.24, 119.99, 120.62, 121.92, 75.48, 73.51, 103.58*, 135.83 122.35, 122.81, 124.62*, 107.09*, 115.96*, 126.24, 127.41*, 128.20, 128.46, 131.50* 130.08*, 130.15*, 130.28*, 131.04*,131.30, 132.09*, 135.83, 144.64*, 150.87*, 151.61*, 155.68*  Cp 78.88  77.94, 78.09  77.89, 78.03  77.85  77.86, 77.61, 74.77  80  Analysis of the allyl capped star-shaped molecules (3.13-3.16) showed that the compounds were pure as seen in the close match between the calculated elemental analysis and the experimental results for elemental analysis. The yields were higher for those starshaped molecules that did not require column chromatography for purification from the mono- and di-substituted products. Results may be seen in table 3.5. Table 3.5 Percent yields and elemental analysis of 3.13-3.16 Compound Percent Elem. Anal. Elem. Anal. Calc. yield (%) (g/mol) 57 C117H96O12Fe6P6F36 C: 48.48; H: 3.38 3.13 2898.9 79 C168H135O18Fe9P9F54 C: 47.49; H: 3.20 3.14 4349.2 97 C219H174O24Fe12P12F72 C: 46.98; H: 3.13 3.15 5599.5 70 C270H213O30Fe15P15F90 C: 46.66; H: 3.09 3.16 6949.8  Elem. Anal. Found C: 48.53; H: 3.41 C: 47.63; H: 3.39 C: 46.82; H: 3.10 C: 46.81; H: 3.12  These star-shaped molecules were further analyzed using viscometry and thermal analysis. A summary of the analysis may be found in table 3.6. A 35-50% weight loss was noted between 230 oC and 280 oC. This corresponded to the cyclopentadienyliron moiety that was thermally cleaved from the star-shaped backbone. The second degradation occurred to a lesser extent between 410 oC and 520 oC corresponded to the breakdown of the polyether linkages. The glass transition temperatures were found to increase with increasing number of metal moieties up to 15 metals, at which point the glass transition temperature decreased drastically to the range of the tri- and hexa-metallic star-shaped molecules.  81  Table 3.6 Thermal analysis and viscosity data for 3.12-3.16 (DSC to 200 oC and TGA to 600 oC) Weight Tonset Tendset Weight Tonset Tendset Tg Inherent o o o o o Loss (%) ( C) ( C) ( C) Loss (%) ( C) ( C) Viscosity (dL/g) 39 260 275 18 441 509 129 3.12 36 241 273 20 447 509 123 0.17 3.13 46 246 272 17 438 509 140 0.15 3.14 35 238 257 28 443 519 169 0.14 3.15 34 230 253 24 408 509 129 0.11 3.16  Inherent viscosity of the allyl-capped star-shaped molecules was tested in DMSO at 25.0 oC using a Brookfield DVII+ viscometer at 100 RPM. A plot of the inherent viscosity at varying concentrations shows the polyelectrolyte effect as may be seen in figure 3.5. This is expected given the presence of the positively charged iron moiety. Reported values are given for a concentration of 0.5 g/dL using the equation of the line for the values outside of the polyelectrolyte effect. It may be noted that as the molecular weight increased, the inherent viscosity was found to decrease. The solubility of these star-shaped molecules was found to be moderate, even with higher numbers of metallic units. The trimetallic compound was soluble in most polar organic solvents such as acetone, dichloromethane, DMF and DMSO. Upon moving to the star-shaped molecule with 15 metals, the solubility was noted to decrease and the product was soluble in only DMF and DMSO.  82  Figure 3.5 Viscosity of 3.13 as determined in DMSO at 25 oC at 100 RPM. 55  Inherent Viscosity  50 45 40 35 30 25 20 15 10 0  0.002  0.004  0.006  0.008  0.01  0.012  Concentration (g/mL)  3.2.2 Synthesis and properties of ester-containing star-shaped molecules The influence of the introduction of an ester linkage in each star arm was then probed via the synthesis of star-shaped molecules containing an ester linkage in place of one of the ether linkages in the star-arm backbone. The first step in preparing these compounds was the synthesis of a carboxylic acid containing chain. This was achieved using a different methodology than previously reported.135,151,155 This may be seen in scheme 3.3. Various cyclopentadienyliron complexes may be coupled via nucleophilic aromatic substitution to 4-hydroxybenzoic acid using a large excess of the carboxylic acid in the presence of potassium bicarbonate at elevated temperature using a mixed solvent system.  83  Cl  O  M R 2.1 or 1.37a, b M=Fe+PF6-Cp  HO OH 2.2 K2CO3, 60oC O M  O  R  OH  2.3, 3.17, 3.18  OH 3.11 or 3.19 HO  DCC/DMAP  OH  O O O O M R  M R  M O n  O n  M  O  O O M  O n  O  O  O R O  M O  3.20a, n = 0, R = Cl b, n = 0, R = CH3 c, n = 0, R = H  3.21a, n = 1, R = Cl b, n = 1, R = CH3 c, n = 1, R = H  Scheme 3.3  84  Following the preparation of the carboxylic acid containing chain, the star-shaped molecule could then be prepared. This was reliably accomplished using DCC/DMAP as an esterification system. Proton NMR was used as a judge of purity of star-shaped material. Incomplete reaction lead to the presence of free phenolic groups on the central core which are readily present in the 1H NMR spectra in the range of 9-10 ppm. Purification, when necessary from the mono- and di-substituted products was carried out using column chromatography. This resulted in a decrease of yield and occurred most often when other esterification conditions were used such as preparation of an acid chloride via reaction of the alcohol with thionyl chloride in the presence of the base diethylamine.  Figure 3.6 1H NMR spectrum of 3.20a in DMSO-d6 (at 200 MHz) As is visible in figure 3.6, the 1H NMR of 3.20a clearly shows the cyclopentadienyl resonance at 5.32 ppm. The single aromatic proton shift, corresponding to the three hydrogens of the star-shaped core, appears as a singlet at 7.40 ppm. The aromatic benzoate  85  protons were split into a set of doublets each of six hydrogens. The doublet at 8.28 ppm had splitting of 7.8 Hz and the doublet centered around 7.52 ppm had J coupling of 8.6 Hz. The complexed aromatics appeared as a set of doublets with J coupling of 6.6 Hz at 6.88 and 6.61 ppm. Each doublet corresponded to six hydrogens. The large singlet at approximately 3.25 ppm corresponds to water introduced via the NMR solvent. Residual DMSO may be seen at 2.49 ppm. Table 3.7 gives the 1H NMR analysis for each of the linear star-shaped molecules containing ester linkages. Table 3.7 1H NMR values of 3.20 and 3.21 in DMSO-d6 Aromatics Complexed Ar. 7.40(s, 3 H), 7.52(d, 6.61(d, J=6.6, 6 H), 3.20a J=8.6, 6 H), 8.28(d, 6.88(d, J=6.6, 6 H) J=7.8, 6 H) 7.46(d, J=5.5, 15 H), 6.34(d, J=9.4, 12 H), 3.21a 7.52(d, J=9.0, 6 H), 6.60(d, J=7.0, 6 H), 8.27(d, J=8.6, 6 H) 6.89(d, J=6.6, 6 H) 7.40(s, 3 H), 7.48(d, 6.33(d, J=6.6, 6 H), 3.20b J=8.6, 6 H), 8.27(d, 6.45(d, J=7.0, 6 H) J=8.9, 6 H) 7.42(s, 15 H), 7.48(d, 6.33(d, J=6.6 12 H), 3.21b J=7.8, 6 H), 8.26(d, 6.43(d, J=6.6, 6 H), J=8.3, 6 H) 6.78(d, J=6.3, 6 H) 7.41(s, 3 H), 7.52(d, 6.23(br s, 3 H), 3.20c J=7.8, 6 H), 8.29(d, 6.43(br d, J=12.5, 12 J=8.2, 6 H) H) 7.35(s, 3 H), 7.45(d, 6.22(d, J=7.4, 6 H), 3.21c J=7.8, 12 H), 7.51(d, 6.43(d, J=10.2, 12 H), J=8.6, 6 H), 8.27(d, 6.62(d, J=7.0, 6 H) J=9.0, 6 H)  Cp + CH3 5.32(s, 15 H)  5.32(s, 30 H)  5.18(s, 15 H) 2.39(s, 9 H) 5.18(s, 15 H), 5.31(s, 15 H), 2.39(s, 9 H) 5.21(s, 15 H)  5.21(s, 15 H), 5.29(s, 15 H)  The 13C NMR data may be seen in table 3.8 for the linear ester containing star-shaped molecules. The spectrum of compound 3.20b may be seen in figure 3.7. From the figure, the star core carbons with attached protons appeared at 114.56 ppm, whereas the benzoate carbons with attached protons were present at 120.44 and 133.05 ppm. The quaternary carbons are clearly visible resonating at 129.96, 151.46 and 158.90 ppm. The quaternary  86  complexed aromatic carbon appeared as upward peaks at 101.39 ppm and 158.90 ppm. The complexed aromatic carbons with attached hydrogens were present at 78.17 and 87.27 ppm. The cyclopentadienyl carbons resonated at 78.04 ppm and the carbonyl carbon appeared at 163.66 ppm. The methyl carbon was found at 34.40 ppm while the strong resonance at 39.5 ppm is that of residual DMSO in the deuterated solvent.  Figure 3.7 13C ATP NMR of 3.20b in DMSO-d6 (at 200 MHz)  87  Table 3.8 13C NMR values for 3.20 and 3.21 in DMSO-d6 Aromatics Complexed Aromatic  3.20a 3.21a  3.20b 3.21b  3.20c 3.21c  114.29, 120.39, 132.80, 130.24*, 151.14*, 158.19* 111.66, 120.46, 121.78, 124.157, 132.70, 148.07*, 150.94*, 153.66*, 156.20*, 157.96* 114.56, 120.44, 133.05, 129.96*, 151.46*, 158.90* 110.65, 120.27, 121.67, 124.17, 132.75, 130.51*, 148.15*, 151.05*, 156.38*, 158.36* 114.10, 120.36, 132.79, 130.82*, 151.17*, 158.00* 109.87, 120.41, 121.60, 124.14, 132.69, 130.93*, 148.14*, 150.94*, 156.40*, 158.11*  77.99, 87.01, 104.15*, 152.85* 75.08, 76.33, 78.23, 87.01, 104.11*, 126.13*, 129.91*, 130.35* 78.17, 87.27, 101.39*, 125.78* 75.05, 76.00, 78.12, 86.99, 101.07*, 125.86*, 129.59*, 129.91* 78.46, 85.58, 87.00, 125.64* 75.02, 76.07, 78.30, 85.50, 86.92, 125.95*, 129.16*, 130.48*  Cp 79.66  Aliphatic, Carbonyl 163.31*  79.64, 77.87  163.59*  78.04 77.77, 77.69  34.40, 163.66* 34.10, 163.74*  77.35  163.43*  77.26, 78.08, 163.67*  As may be seen from the yields presented in table 3.9, purification from the monoand di-substituted products causes a decrease in the yield of the product. As a result, the yields ranged from 35-90 %. Elemental analysis confirmed the molecular weight of the structures proposed by analysis of the NMR and based upon the added starting materials. Table 3.9 Percent yields and elemental analysis of 3.20, 3.21 Percent Elem. Anal. Elem. Anal. Calc. Yield (%) (g/mol) 65 C60H42O9Cl3Fe3P3F18 C: 44.60; H: 2.62 3.20a 1615.8 65 C111H81O15Cl3Fe6P6F36 C: 44.95; H: 2.75 3.21a 2966.1 47 C63H51O9Fe3P3F18 C: 48.68; H: 3.31 3.20b 1554.5 90 C114H90O15Fe6P6F36 C: 47.14; H: 3.12 3.21b 2904.8 35 C60H45O9Fe3P3F18 C: 47.65; H: 3.00 3.20c 1412.4 77 C111H84O15Fe6P6F36 C: 46.57; H: 2.96 3.21c 2862.7  Elem. Anal. Found C: 44.73; H: 2.60 C: 44.98; H: 2.76 C: 48.66; H: 3.27 C: 47.36; H: 3.19 C: 47.74; H: 3.02 C: 46.66; H: 3.04  88  Thermal analysis of the tri-substituted star-shaped molecules (pure, table 3.10), showed that decomplexation of the cyclopentadienyliron moiety occurred between 210 oC and 300 oC. The second weight loss observed in the TGA corresponds to the breakdown of the ester/ether backbone. This occurred between the temperatures of 320 oC and 460 oC. These temperatures for backbone degradation, when compared to the linear, ester free starshaped molecules of similar size and number of metal moieties were decreased by almost 100 oC. This illustrates that the presence of the ester linkage causes decreased thermal stability. The glass transition temperatures were found in the range of 160-195 oC. This is lower than those of linear polyethers, which do not display glass transition temperatures below the degradation temperature. Table 3.10 Thermal analysis of 3.20, 3.21 (DSC to 200 oC, TGA to 500 oC) Weight Tonset (oC) Tendset Weight Tonset Tendset o o Loss (%) ( C) (oC) Loss (%) ( C) 27 214 302 24 364 392 3.20a ‘pops’ 3.21a 38 224 261 11 349 395 3.20b 28 238 253 12 395 424 3.21b 21 214 246 23 321 378 3.20c 32 233 237 17 444 460 3.21c  Tg 172 189 194 172 160 176  3.2.3 Synthesis and properties of ester-containing singly branched star-shaped molecules (1st generation dendrimers) The influence of a second branch point on the thermal stability was of the starshaped molecules was also investigated. The first step to this end was that of the synthesis of non-linear carboxylic acid containing chains that were prepared by nucleophilic aromatic substitution  of  the  desired  cyclopentadienyliron  complex  and  4,4-bis(4-  hydroxyphenyl)valeric acid. Compound 1.33 had been previously prepared by this  89  methodology.136,141,151-154 This branched or Y shaped chain was then reacted with the starshaped core to give the singly branched star-shaped molecules via an esterification reaction. This may be seen in scheme 3.4. Moderate yields were found for these star-shaped molecules (table 3.11). OH  HO M  R  Cl  2.1, R = Cl 1.37b, R = CH3 1.37a, R = H M=Fe+PF6-Cp  HO  O 3.22  K2CO3  O  OH  R  R M  M O  O 1.33, R = Cl 3.23a, R = H 3.23b, R = CH3  3.11 DCC/DMAP  M  O  R  O O  M  O  R O  M M  O  R  O O  M O  R  O  M  O  M O  O  O  O O O  O  M  R  3.24a, R = Cl b, R = CH3 c, R = H  M R  Scheme 3.4  90  Table 3.11 Percent yields and elemental analysis for 3.24  3.24a  Percent yield (%) 66  3.24b  65  3.24c  72  Elem. Anal. (g/mol)  Elem. Anal. Calc.  C174H141O18Cl6Fe9P9F54 4540.0 C180H159O18Fe9P9F54 4417.5 C174H147O18Fe9P9F54 4333.4  C: 46.03; H: 3.13  Elem. Anal. Found C: 46.29; H: 3.18  C: 48.94; H: 3.63  C: 48.84; H: 3.62  C: 48.23; H: 3.42  C: 48.12; H: 3.36  As may be seen in figure 3.8 or table 3.12, the 1H NMR spectrum of the methyl capped bis-valeric acid derivative (3.23b) displays the expected symmetry of the molecule. The molecular symmetry causes the two cyclopentadienyliron complexes as well as the aromatic rings of the bis-valeric acid to appear with the same shift since they experience the same electronic environment. The cyclopentadienyl protons appear as a singlet integrating for ten hydrogens at 5.12 ppm and the complexed aromatics also showed up as a singlet at 6.25 ppm, accounting for eight hydrogens. The magnet strength of the 200 MHz NMR was insufficient to resolve the expected doublet for the complexed aromatics. The aromatics derived from the bis-valeric acid appeared as doublets of four hydrogens each with coupling of 8.0 Hz at 7.24 and 7.36 ppm. The remaining aliphatic protons belonging to that of the valeric acid appeared at 1.68 ppm (methyl group), 2.08 and 2.28 ppm for the methylene groups, while the methyl group attached to the complexed aromatic was visible at 2.35 ppm. Water introduced via the NMR solvent may be seen as the singlet at approximately 3.25 ppm. Spinning side bands may also be seen in figure 3.8. Compound  1.33 has been previously published.135,151,155  91  Table 3.12 1H NMR values and yields of 3.23a,b Yield Aliphatics Cp Complexed (%) Aromatics 54 1.76 (s, 3H, CH3), 2.50 5.26 (s, 6.29 (br s, 3.23a (br s, 4H, CH2) (Acetone) 10H) 2H), 6.406.48 (m, 8H) 56 1.68 (s, 3H, CH3), 2.08 5.12 (s, 6.25 (s, 8H) 3.23b (t, 2H, CH2), 2.28 (t, 2H, 10H) (DMSO) CH2), 2.35 (s, 6H, CH3)  Aromatics 7.34 (d, J = 7.4 Hz, 4H), 7.49 (d, J = 8.2 Hz, 4H) 7.24 (d, J = 8.0 Hz, 4H), 7.36 (d, J = 8.0 Hz, 4H)  Figure 3.8 1H NMR spectrum of 3.23b in DMSO-d6 (at 200 MHz) The 13C NMR confirms that of the 1H NMR for compound 3.23b. In this (figure 3.9 and table 3.13), the methyl group belonging to the complex may be found at 19.23 ppm whereas the methyl group of the valeric acid was present at 26.91 ppm. The methylene carbons were present at 29.74 and 36.09 ppm and the quaternary carbon from the valeric acid at 44.92 ppm. The cyclopentadienyl carbons resonated at 77.34 ppm and were bracketed by the complexed aromatic CHs at 76.11 and 86.68 ppm. The quaternary complexed aromatics were found at 100.20 and 131.36 ppm. The aromatics from the bis-  92  valeric acid were clearly visible at 119.99 and 129.14 ppm with the quaternary carbons at 146.00 and 151.26 ppm. The carbonyl carbon of the valeric acid appeared at 174.82 ppm and residual DMSO carbons at 39.5 ppm. Table 3.13 13C NMR values of 3.23a,b Aliphatics  3.23a 3.23b  Cp, Carbonyl 27.86 (CH3), 28.64 (CH2), 78.06, 37.36 (CH2), 46.25 (C) 175.56* 19.23 (CH3), 26.91 (CH3), 77.34, 29.74 (CH2), 36.09 (CH2), 174.82* 44.92 (C)  Complexed Ar  Aromatics  77.73, 85.72, 87.81, 134.46* 76.11, 86.68, 100.20*, 131.36*  121.35, 130.50, 147.77*, 152.11* 119.99, 129.14, 146.00*, 151.26*  Figure 3.9 13C APT NMR of 3.23b in DMSO-d6 (at 200 MHz) Upon formation of the star-shaped molecule with the branched chain, a noticeable decrease in solubility was noted. Successful formation of the star-shaped molecule was deduced by analysis of the 1H and  13  C NMR spectra. For the methyl capped derivative  prepared (3.24b), the 1H NMR showed the appearance of the central core complexed arene protons at 6.26 ppm (figure 3.10). The valeric acid based complexed aromatics appeared as two doublets at 6.52 ppm (J = 6.0 Hz) and 6.33 ppm (J = 8.0 Hz), with each doublet corresponding to six hydrogens for the complexed aromatics. The aromatics from the core 93  resonated at 7.32 ppm as a singlet. The valeric-based aromatics were visible at 7.40 ppm and 7.27 ppm. The central cyclopentadienyl protons were visible at 5.24 ppm whereas the cyclopentadienyl protons associated with the bis-valeric derivative on the outside of the star-shaped molecule were visible at 5.12 ppm. The methyl group associated with the complexed aromatic appeared as a singlet at 2.36 ppm whereas the methyl group associated with the valeric acid appeared at 1.73 ppm. The methylene groups were visible within the broad singlet at 1.73 ppm. Water in the NMR solvent accounts for the large singlet at approximately 3.25 ppm whereas the peak at 2.49 ppm relates to the residual DMSO in the deuterated solvent. DCM is also visible within the spectra at approximately 5.6 ppm. These may be seen in figure 3.10 and displayed in table form along with the other two branched ester containing star-shaped molecules in table 3.14. Table 3.14 1H NMR values of 3.24 in DMSO-d6 Aliphatics Aromatics 3.24a 1.65 (br. s, 9H, 7.02(d, J=8.6, 6 H), CH3), 1.70 (t, 6H, 7.11(d, J=7.9, 6 H), CH2), 1.73 (t, 6H, 7.32(s, 15 H), 7.41(s, 12 H) CH3)  Complexed Aromatic Cp 6.31(d, J=6.6, 12 H), 5.28(s, 45 H) 6.43(d, J=7.0, 12 H), 6.81(d, J=6.6, 12 H)  3.24b  1.73(br s, 21H, 7.27(d, J=7.5, 12 H), 6.26(s, 24 H), 5.12(s, 30 H), CH3, CH2), 2.36 7.32(s, 15 H), 7.40(d, 6.33(d, J=8.0, 6 H), 5.24(s, 15 H) (s, 18H, CH3) J=6.1, 12 H) 6.52(d, J=6.0, 6 H)  3.24c  1.70 (br s, 15H, 6.95(d, J=23.6, 6 H), 6.18(br. s, 6 H), 5.16(s, 30 H), CH3, CH2), 1.75 7.11(d, J = 9.0, 6 H), 6.32(s, 24 H), 6.63(d, 5.25(s, 15 H) (m, 6H, CH2) 7.32(s, 15 H), J=6.6,12 H) 7.41(s, 12 H)  94  Figure 3.10 1H NMR spectrum of 3.24b in DMSO-d6 (at 200 MHz) The 13C NMR was used to confirm the results of the 1H NMR analysis. This may be seen for compound 3.24b in figure 3.11 and the results for 3.24a-c are listed in table 3.15. The complexed aromatics appeared at 76.23 and 86.72 ppm and the cyclopentadienyl carbons were visible at 77.39 ppm for the external bis-valeric acid derivative complexes and at 78.06 for the internal core complexes. The quaternary complexed carbons were found at 100.29, 128.94, 130.43 and 131.33 ppm. The aromatics corresponding to the core were found at 121.40, 124.01 ppm and the quaternary aromatics corresponding to the core were at 148.11, 156.38 ppm. The aromatics corresponding to the valeric acid derivative were visible at 120.07, 129.23 ppm and the quaternary aromatics corresponding to the valeric acid derivative were visible at 145.82 and 151.45 ppm. The aliphatic carbons were found at 19.27 and 27.00 ppm for the CH3s and 30.00 ppm for the CH2 and 44.99 ppm for the quaternary carbon. The carbonyl carbon was found at 171.67 ppm whereas the residual DMSO in the deuterated solvent was found at 39.5 ppm. DCM solvent accounts for the resonance at approximately 55 ppm, while the peak at 99 ppm was found to have no area. 95  Table 3.15 13C NMR values of 3.24 in DMSO-d6 Aliphatics Aromatics  3.24a  27.05 (CH3), 29.78, 30.13 (CH2), 45.06*  3.24b  19.27, 27.00 (CH3), 30.00 (CH2), 44.99*  3.24c  27.05 (CH3), 29.81, 35.95 (CH2), 45.05*  Complexed Aromatics 120.19, 121.50, 76.40, 86.80, 124.00, 129.34, 103.61*, 131.88* 146.14*, 148.09*, 151.22*, 159.75* 120.07, 121.40, 76.23, 86.72, 124.01, 129.23, 100.29*, 128.94*, 145.82*, 148.11*, 130.43*, 131.33* 151.45*, 156.38* 109.95, 120.27, 75.03, 75.97, 121.36, 123.97, 77.77, 84.81, 129.29, 132.52*, 86.71, 128.83*, 146.00*, 148.05*, 130.39*, 131.88* 151.14*, 156.32*  Cp and Carbonyl 79.34, 78.04, 171.66  77.39, 78.06, 171.67  76.82, 78.04, 171.69  Figure 3.11 13C APT NMR of 3.24b in DMSO-d6 (at 200 MHz) The thermal properties of the ester containing stars containing a single branch were tested and the results may be seen in table 3.16. As may be seen, the initial weight loss was found to occur between 225 oC to 260 oC and this corresponded to the loss of the  96  cyclopentadienyliron moiety. The second weight loss, related to the breakdown of the starshaped molecules backbone, occurred between 340 oC and 460 oC. The backbone degradation temperatures were, once again, approximately 100 oC lower than those for starshaped molecules that did not contain an ester linkage. The temperature region of the loss of the cyclopentadienyliron moiety did not change significantly with the incorporation of the ester linkage into the molecules backbone. The introduction of a single branch into the star-shaped molecule may have increased the temperature at which the backbone degraded by a small amount (20 oC). The glass transition temperatures were found to have not changed dramatically in relationship with the other star-shaped molecules prepared and were found to occur between 150 oC and 175 oC. Table 3.16 Thermal analysis of 3.24 Weight Tonset (oC) Tendset Loss (%) (oC)  3.24a 3.24b 3.24c  24 20 26  226 236 238  247 252 254  Weight Loss (%) 25 37 33  Tonset (oC)  Tendset (oC)  Tg  343 388 398  403 458 430  170 151 171  3.2.4 Other star-shaped molecules attempted and tested Attempts at preparing dendrimers based on the elongation of the singly branched arms of compound 3.24a were met with extremely low yields, with most of the material being of the di-substituted product. Upon the building of three-dimensional models using organic modeling kits, it became readily apparent the cause of this was most likely steric hindrance of the larger arms to the central core. It was also found that attempts at preparing star-shaped molecules with a single methylene between the carboxylic acid and the phenyl group for the arm were unsuccessful using several different sets of esterification conditions.  97  The glass transition temperatures of the star-shaped cores and linear star-shaped molecules containing the cyclopentadienyliron complex as the end cap were found. The synthetic conditions for the preparation of these as well as the thermogravimetric analysis have been published by previous members of the Abd-El-Aziz group.133 The glass transition temperatures for the complex capped star-shaped molecules were found to exhibit the same trend as the allyl-capped star-shaped molecules. This trend being the increase in Tg with increasing number of metals followed by a large drop for the starshaped molecule containing 15 metals. The inherent viscosity of the central cores was also determined for a concentration of 0.5 g/dL. The polyelectrolyte effect was seen for both sets of compounds. Insufficient quantity of the remaining sample of 3.25b did not allow for characterization of the inherent viscosity or the polyelectrolyte effect. These values may be seen in table 3.17. Structures of these compounds may be seen in figure 3.12. Table 3.17 Glass transitions of 3.10, 3.11, 3.25 and viscosity of 3.10, 3.12, 3.25a,c,d 3.10 3.11 3.25a 3.25b 3.25c 3.25d Tg 185 197 148 175 170 130 Viscosity 0.089 0.16 0.15 --0.15 0.14  98  M O n O M O  O  M  M  O n  O O M O  3.25a n = 1 b n = 2 c n = 3 d n = 4 M=Fe+PF6-Cp  O  n M  Figure 3.12: Structure of 3.25a-d  3.2.5 Viscometric studies of cylcopentadienyliron compounds Two series of star-shaped cyclopentadienyliron compounds (3.13-16, 3.25a,c,d) along with the starting star-shaped cores (3.10, 3.11) were used as viscosity calibrants. As such, the viscosity, in centipoises was tested manually over a range of concentrations. The values were then converted to relative, specific, reduced and inherent viscosities using equations 1.4 thru 1.8 as set up in an excel spread sheet. Since the compounds were expected to act as polyelectrolytes, the reciprocal of the reduced viscosity and the square root of the concentration as needed for the Fuoss plot were also calculated. Graphing, in excel, of the inherent viscosity versus the concentration illustrated the polyelectrolyte effect for the tested compounds. An example of this effect was for star 3.13 in figure 3.5. The polyelectrolyte effect was seen in all compounds tested with the omission of the small trimetallic star-shaped core 3.10. Following viscometric analysis, the sample of  3.10 was precipitated into 10% HCl in the presence of ammonium hexafluorophosphate,  99  filtered and allowed to dry. The presence of the cyclopentadienyl unit was confirmed to still be present by its appearance in the 1H NMR spectra. A second graph, also prepared in excel, shows both the Huggins and the Kramer plots used for the determination of the intrinsic viscosity omitting the concentrations that were clearly within the polyelectrolyte effect region. The equation of the line for the Kramer plot was necessary to determine the commonly reported value of the inherent viscosity at 0.5 g/dL. Figure 3.13 shows both the Huggins and Kramer plots for star 3.11  Reduced + Inherent V iscosity (m L/g)  along with the equations of the line. 24 22 20 18 16 14 12 10 8 0.001  0.003  0.005 0.007 0.009 Concentration (g/mL)  Reduced Viscosity Linear (Reduced Viscosity) y = -1138.7x + 22.627  0.011  Inherent Viscosity Linear (Inherent Viscosity) y = -1167.9x + 22.203  Figure 3.13 Classic Kramer (Inherent Viscosity) and Huggins (Reduced Viscosity) plots outside of the polyelectrolyte region for star 3.11.  A third graph of the Fuoss plot was used for the determination of the intrinsic viscosity of the polyelectrolytes as seen in figure 3.14. Each of the graphs were prepared with the inherent and reduced viscosities in g/mL. The scatter seen within the graphs of both the inherent viscosity and the reduced viscosity versus the concentration is due to a combination of changing barometric pressure, viscoelasticity of the samples and the  100  manual nature of the operation of the viscometer. Table 3.18 shows the intrinsic viscosity of each of the star-shaped molecules as determined from each of the three equations (Huggins, Kramer and Fuoss). Table 3.18 also gives the constants associated with the three  y = 0.8033x + 0.005  0.1 0.09 0.08 0.07 (mL/g)  Recipricol of the Reduced Viscosity  different plots when the intrinsic viscosity is reported in g/mL.  0.06 0.05 0.04 0.03 0.02 0.01 0 0.01  0.03  0.05  0.07  0.09  0.11  Square Root of Concentration (g/mL)  Figure 3.14 Fuoss plot for star 3.11.  Table 3.18 Intrinsic viscosities and constants determined by graphing of the data [η] kH [η] kK kH + k K [η] Huggins Kramer Fuoss 7.19 1.77 7.19 -1.16 0.61 5.48 3.10 22.63 -2.22 22.20 2.37 0.15 200.00 3.11 20.48 -1.37 20.62 1.56 0.19 70.92 3.13 15.96 -1.00 15.66 1.23 0.23 18.73 3.14 12.25 0.16 12.18 -0.27 -0.11 13.93 3.15 13.97 -3.40 13.91 3.67 0.27 20.75 3.16 16.36 -1.27 16.52 1.47 0.20 38.91 3.25a 15.65 -1.05 15.29 0.80 -0.25 12.29 3.25c 36.54 -2.50 36.48 2.85 0.35 86.96 3.25d  viscometric B -2.98 160.66 40.41 4.25 1.22 13.91 20.58 -1.12 51.75  As seen in table 3.18, the intrinsic viscosity determined by each of the methods is different, omitting star 3.10. The difference between the Huggins and the Kramer plots is  101  minor whereas the difference between both of these and the Fuoss plot is, in most cases extreme. This may be due to the non-linear nature of the lines formed by the Huggins and Kramer plots or by scatter present in the Fuoss plots as seen in figures 3.13 and 3.14. When the polyelectrolyte region is included within the Huggins and Kramer plots, the intrinsic viscosity values increase but do not approach those from the Fuoss plot. As the compounds tested are star-shaped, a value of 0.5 for the addition of the Kramer and Huggins plots was not expected. The values ranged between -0.25 and 0.61 with most around 0.20. Interestingly, the star-shaped molecules containing six metals (3.14 and 3.25a) gave similar values as did the star-shaped molecules containing twelve metals (3.15 and 3.25c). The large absolute value of the Huggins constant and the positive nature of the Kramer constant suggest that spherical molecules were formed in solution. As the molecular weights of the star-shaped molecules were known by their discrete structure (as confirmed by NMR spectroscopy and elemental analysis), a Mark-Houwink plot may be drawn as seen in figure 3.15 using the data in Table 3.19 where the intrinsic viscosity has been converted to dL/g from mL/g to be comparable to literature values. In this double log plot of the intrinsic viscosity versus the molecular weight, the equation of the line gives the values α and k in the Mark-Houwink equation (equation 1.10). Since the intrinsic viscosity values for the Huggins and the Kramer plots are similar, only the Huggins plots was used in calculations. The constant k has a value of 0.002384 dL/g while α has a value of 0.2362 when the intrinsic viscosity from the Huggins equation is used. The value for α was found to be 0.1648 and k to be 0.1135 dL/g when the values from the Fuoss equation were used. The low α values corresponds to the star-shaped compounds acting as  102  spheres in the chosen solvent and that the use of this α value for the calculation of the molecular weights of linear polymers is inappropriate via the Mark-Houwink equation. Table 3.19 Intrinsic viscosity and molecular weights as used for the Mark-Houwink plots  log [Intrinsic Viscosity]  3.10 3.11 3.13 3.14 3.15 3.16 3.25a 3.25c 3.25d  Molecular Weight (g/mol, MW) 1255.4 1476.4 2898.8 4249.2 5599.5 6949.8 2544.5 5254.1 6595.4  -0.5 -0.7 3 -0.9  logMW 3.0987 3.1692 3.4622 3.6283 3.7481 3.8420 3.4056 3.7205 3.8192  3.2  [η] Huggins 0.00719 0.02263 0.02048 0.01596 0.01225 0.01397 0.01636 0.01565 0.03654  3.4  log[η] Huggins -2.1433 -1.6453 -1.6887 -1.7970 -1.9119 -1.8548 -1.7862 -1.8055 -1.4372  3.6  [η] Fuoss 0.00548 0.20000 0.07092 0.01873 0.01393 0.02075 0.03891 0.01229 0.08696  3.8  log[η] Fuoss -2.2612 -0.6990 -1.1492 -1.7275 -1.8560 -1.6830 -1.4099 -1.9104 -1.0607  4  -1.1 -1.3 -1.5 -1.7 -1.9 -2.1 -2.3 -2.5 log MW Huggins  Fuoss  Linear (Huggins) y = 0.2362x - 2.6226  Linear (Fuoss) y = -0.1648x - 0.9444  Figure 3.15 Mark-Houwink plots for the star-shaped molecules, including the equations of the lines Due to the amount of scatter in the prepared Mark-Houwink plot of all of the starshaped molecules tested, the two series of star-shaped molecules were analyzed separately to see if there was a dependence on the general structure of the molecule. The MarkHouwink plot for those star-shaped molecules which had a cyclopentadienyliron complex  103  at the periphery may be seen in figure 3.16 along with the equation of the line. The constant k was found to be 2.855 x 10-5 dL/g while the value for α was 0.7837 based upon the Huggins data. The Mark-Houwink constants based upon the calculated intrinsic viscometry from the Fuoss equation were k equal to 2.869 x 10-6 dL/g and α equal to 1.1056. Based upon these α values, these star-shaped molecules were not spherical in nature but rather acted as random coils more characteristic of linear polymers.  log[Intrinsic Viscosity]  -1 -1.2  3  3.2  3.4  3.6  3.8  4  -1.4 -1.6 -1.8 -2 -2.2 -2.4 log MW Huggins  Fuoss  Linear (Huggins)  y = 0.7837x - 4.5444  Linear (Fuoss) y = 1.1056x - 5.5422  Figure 3.16 Mark-Houwink plots for star-shaped molecules with cyclopentadienyliron complexes at the periphery (3.10, 3.25a,c,d)  The Mark-Houwink plot and equation of the line for those star-shaped molecules with an organic end group appear in figure 3.17. From the equation of the line for the Huggins data, the constant k was 0.3973 mL/g while α was 0.3862. Using the Fuoss equation data, α was 1.7248 and the constant k was 5.425 x 104 mL/g. The low α value from the Huggins data was indicative of spheres and thus the star-shaped molecules are folded back upon themselves into a ball. The Fuoss data suggested that the star-shaped molecules were elongated in nature. As may be noted, the slope of the line is opposite the  104  previous plot. The direction of this slope is indicative of compounds that may be used to  log[Intrinsic Viscosity]  enhance fluidity and flow in solvents.  -0.6 3 -0.8  3.2  3.4  3.6  3.8  4  -1 -1.2 -1.4 -1.6 -1.8 -2 log MW Huggins  Fuoss  Linear (Huggins)  y = -0.3862x - 0.4009  Linear (Fuoss) y = -1.7248x + 4.7344  Figure 3.17 Mark-Houwink plots for star-shaped molecules with an organic group at the periphery (3.11, 3.13-3.16)  Due to these conflicting results of the Mark-Houwink plots, confirmation of spherical nature suggested by the Kramer and Huggins constants of the star-shaped molecules is necessary to determine if the compounds are indeed spherical and hence that the Mark-Houwink equation becomes invalid. Thus, the molecular compactness (ρ) and shrinking factors (g, h) were determined. The shrinking factors required that analysis of the linear polymers with known approximate molecular weights by GPC also be subjected to viscometric analysis. These descriptive values required that first the hydrodynamic volume and the viscometric volume be calculated. Calculation of the intrinsic viscosity values of the linear polymers along with the Kramer, Huggins and Fuoss constants was undertaken. The intrinsic viscosity was required to calculate the molecular compactness and shrinking factors for comparison to the star-  105  shaped molecules. These values may be seen in table 3.20. As may be seen by the differences in the intrinsic viscosity values, the chosen solvent was not ideal for these compounds. The Huggins and Kramer constants as well as their product suggest that the compounds are forming spheres. This may be due to the use of a non-ideal solvent, the polyelectrolyte ion sphere or the low molecular weights as determined by GPC for these polymers. Table 3.20 Intrinsic viscosity values and related constants for the linear polymers [η] kH [η] kK kH + k K [η] B Huggins Kramer Fuoss 27.17 -0.67 26.55 0.92 0.25 40.65 8.63 2.7c 26.70 -0.48 26.22 0.77 0.29 42.92 9.00 2.7e 36.28 -1.50 35.51 1.66 0.16 102.04 43.15 2.9c 38.10 -1.26 37.23 1.42 0.16 93.46 33.88 2.9e  As the molecular weights of the linear polymers may be approximated based upon the weights of the organic analogues as determined by GPC, a Mark-Houwink plot of the data may be constructed after the intrinsic viscosities are converted to dL/g from mL/g (Table 3.21, Figure 3.18). Based upon the plot, the intrinsic viscosity from the Huggins equation gives Mark-Houwink constants α of 0.2582 and k equal to 0.3273 dL/g. This α value suggests that the proposed linear polymers were spherical in nature. The intrinsic viscosity from the Fuoss equation gives different results which are more in line with the structure of the polymers. These values were α equal to 0.6780, or random coils in solution and k equal to 29.51 dL/g.  106  Table 3.21 Intrinsic viscosity values for the linear polymers [calculated organometallic molecular weight from the GPC data] [η] [η] Fuoss MW log MW log [η] log [η] Huggins (g/mol) Huggins Fuoss 0.02717 0.02670 0.03628 0.03810  2.7c 2.7e 2.9c 2.9e  0.04065 0.04292 0.10204 0.09346  11 600 19 100 4 400 5 400  4.06446 4.28103 3.64345 3.73239  -1.5659 -1.5735 -1.4403 -1.4191  -1.3909 -1.3673 -0.9912 -1.0294  log[Intrinsic Viscosity  -0.8 -0.9 3.6  3.7  3.8  3.9  4  4.1  4.2  4.3  4.4  -1 -1.1 -1.2 -1.3 -1.4 -1.5 -1.6 -1.7 Huggins  Fuoss  log MW Linear (Huggins)  y = -0.2582x - 0.4851  Linear (Fuoss)  y = -0.6780x + 1.4700  Figure 3.18 Mark-Houwink plots for the linear polymers based upon the approximate weights calculated from the organic anologues estimated by GPC From these results, the Fuoss plot and equation appears to be more accurate than the Huggins and Kramer plots and equations. Since the Fuoss equation has been proposed to be used for polyelectrolytes, and the compounds tested are polyelectrolytes, this was expected. The majority of the derived topological data from the Huggins equation has suggested spherical molecules whereas the Fuoss equation data has suggested random coils irregardless of the morphological structure of the compounds tested. As a result, values derived from both sets of equations will be used in an attempt to discern if the star-shaped molecules are spherical and that the Mark-Houwink equation becomes invalid.  107  As the molecular weights of the star-shaped molecules and the linear polymers are known or approximated via an independent method, the viscometric radii, hydrodynamic radii and molecular compactness may be calculated according to equations 1.13, 1.14 and 1.17. The calculated values are presented in table 3.22. The intrinsic viscosities used for calculation of the radii were in dL/g. The Mark-Houwink constants used in calculation of the hydrodynamic radii for the star-shaped polymers were those of figure 3.15, whereas the linear polymers used figure 3.18 to better estimate the shapes of the molecules.  Table 3.22 Viscometric radii (nm), hydrodynamic radii (nm) and molecular compactness (ρ) for the star-shaped molecules and linear polymers where (H) is derived from Huggins data and (F) is derived from Fuoss data Rη (H) RH (H) ρ (H) Rη (F) RH (F) ρ (F) 36 188 0.19 42 3139 0.013 2.7c 43 232 0.19 50 4148 0.012 2.7e 29 125 0.23 41 1825 0.022 2.9c 31 137 0.23 43 2046 0.021 2.9e 11 13 0.85 10 41 0.24 3.10 17 14 1.21 36 44 0.82 3.11 21 19 1.11 31 57 0.54 3.13 22 22 1.00 23 67 0.34 3.14 22 25 0.88 23 74 0.31 3.15 24 27 0.88 28 81 0.35 3.16 18 18 1.00 25 55 0.45 3.25a 23 24 0.96 21 72 0.29 3.25c 33 27 1.22 44 79 0.56 3.25d  As expected, increased molecular weights caused an increase in the size of the molecule. The Mark-Houwink plot containing all of the star-shaped molecules was chosen for calculation of the hydrodynamic radii so that comparisons between the star-shaped molecules could be made. Based upon the viscometric radii, the star-shaped molecules with the organic end group did not increase in size as quickly as those with the organometallic end group when the molecular weight was increased. Comparison of the hydrodynamic  108  radii to end group does not show this trend but does illustrated that the radii is dependent upon size as is illustrated in figure 3.19 and 3.20. The linear relationship between size and molecular weight shows that these star-shaped molecules, although spherical in nature as suggested by α, are not of sufficiently high molecular weight to show significant deviation between the hydrodynamic and viscometric size and the molecular weight. The hydrodynamic radii appear to give a more accurate description of the size in relation to the molecular weight than the viscometric radii due to the use of these compounds in the calculation of the Mark-Houwink constants. However, a slight curvature illustrating the  Viscometric Radii (nm)  spherical nature may be seen (figure 3.20). 50 45 40 35 30 25 20 15 10 5 0 0  1000  2000  3000  4000  5000  6000  7000  8000  Molecular Weight (g/mol) Huggins  Fuoss  Linear (Huggins)  Linear (Fuoss)  Figure 3.19 Graph of the molecular weight of the star-shaped molecules versus the calculated viscometric radii  109  Hydrodynamic Radii (nm)  80 70 60 50 40 30 20 10 1000  2000  3000  4000  5000  6000  7000  Molecular Weight (g/mol) Huggins  Fuoss  Linear (Huggins)  Linear (Fuoss)  Figure 3.20 Graph of the molecular weight of the star-shaped molecules versus the calculated hydrodynamic radii  Molecular compactness values, ρ, may be seen in table 3.22. Polymers 2.7c,e display compactness values much lower than previously reported values. This is most likely due to the poor solvent choice as determined by the differing intrinsic viscosity values between the Huggins and Kramer plots. It may also be related to previous compounds being neutral as opposed to charged or the assumption of viscometric radii that the molecule is spherical. The molecular compactness values derived from the Huggins equation for the star-shaped molecules were consistent with dendrimers of mid generation and hyperbranched polymers. Thus the star-shaped molecules are not overly compact or extended which suggests a spherical shape. When the values derived from the Fuoss equation are examined, they are below those of reported linear neutral polymers. Thus the molecules appear to be extremely compact due to either severe elongation in the solvent or to collapse into a small hard sphere.  110  When estimation of the shrinking factors occurred using the data from the Huggins equation and plot values were found to be similar to previously reported polystyrene data for star and hyperbranched polymers.174 The hydrodynamic shrinking when a star-shaped molecule is constructed over that of a linear molecule was about 70-75%. The geometric shrinking was found to be higher and was between 30-45%. Calculation of the shrinking factors using the Fuoss data gave values below what was expected, possibly due to the ion sphere of the polyelectrolytes tested. These values may be seen in table 3.23. The shrinking factors were calculated using equations 1.15 and 1.16. Table 3.23 Shrinking factors for linear polymers of similar molecular weight to star-shaped molecules where the first value is that derived from the Huggins data and the second in brackets is from the Fuoss data 2.9e vs. 3.25c 2.9e vs. 3.15 2.9c vs. 3.14 molecular weight 5400 vs. 5254 5400 vs. 5600 4400 vs. 4249 g 0.411 (0.132) 0.322 (0.149) 0.440 (0.184) h 0.742 (0.488) 0.710 (0.535) 0.759 (0.561)  To confirm the spherical nature of the star-shaped molecules as suggested by some of the Mark-Houwink plots, the ρ values and the shrinking factors, a graph of the inherent viscosity at a concentration of 0.5 g/dL versus the molecular weight of the star-shaped compounds was prepared (figure 3.21). Based upon this, the star-shaped compounds assume a spherical shape at higher molecular weights consistent with dendrimers. That is, there is a non-linear relationship between the increase in molecular weight and the inherent viscosity. This confirms the spherical nature shown by the Mark-Houwink plot of all of the star-shaped molecules in figure 3.15, the ρ value and the shrinking factors. Thus the MarkHouwink equation prepared from the star-shaped molecules of known weights can not be used for molecular weight estimation.  111  Inherent Viscosity at 0.005g/mL (mL/g)  20 18 16 14 12 10 8 6 0  2000  4000  6000  8000  Molecular Weight (g/mol)  Figure 3.21 Graph of the inherent viscosity of star-shaped molecules versus the molecular weight  Extracting the portion of the graph seen in figure 3.21 wherein the star-shaped compounds show an increase in molecular weight with an increase in size similar to linear molecules may be accomplished via the elimination of the 3.16 and 3.25d or the highest molecular weight star-shaped molecule containing 15 iron units (figure 3.22). These larger star-shaped molecules are, based upon the previous discussion beginning to approximate dendrimers or compact spherical molecules. These do not show a linear increase in size with increases in molecular weight. The equation of the line of the resultant linear plot may be used to relatively approximate the molecular weights of other cyclopentadienyliron compounds. Comparison of the calculated values from this equation of the line to previously reported linear polymers of which GPC had been run showed that the calculated values were overestimated by approximately one third. As a result, the calculated values were scaled down by approximately two thirds to account for the branching of the starshaped compounds.  112  Inherent Viscosity at 0.005g/mL (mL/g)  y = 0.0001925x + 13.0940522  18 16 14 12 10 8 6 0  1000  2000  3000  4000  5000  6000  Molecular Weight (g/mol)  Figure 3.22 Calibration graph with the equation of the line prepared from the inherent viscosity at 0.5 g/dL versus the molecular weight  The molecular weights of the linear polymers as tested by GPC were much lower than those estimated by viscometry using the calibration curve (Table 3.24).  This  discrepancy may be due to any or all of the following reasons: different organometallic versus organic polymer structures/molecular weights due to degradation of the ester linkage during demetallation or to solubility issues of the organic polymer in the extraction media; experimentally determined calibration by star-shaped molecules does not apply well to the structurally different linear polymers, or the choice of solvent is poor; use of polystyrene calibration standards for the GPC do not apply well to the prepared poly(ether-thioetherester) linear polymers.  113  Table 3.24 Molecular weight estimation using the calibration curve for the linear polymers as compared to GPC data ηinh at Un-scaled MW Scaled MW Calculated GPC [0.005g/mL] (g/mol) (g/mol) MW (g/mol) 23.3242 53 100 35 400 11 600 2.7c 23.5655 54 400 36 300 19 100 2.7e 25.0210 62 000 41 300 4 400 2.9c 27.4050 74 300 49 500 5 400 2.9e If degradation of the ester linkage had occurred during demetallation, 1H NMR should have shown the presence of a new and unexpected aliphatic group. This was not the case. However, keeping the organic polymer in solution during the work up was difficult even with the addition of nitromethane to aid in solubility. Loss of the higher molecular weight fraction may have occurred at this step due to insolubility of organic polymer. As seen by the lack of convergence of the Kramer and Huggins plots to give the same value for the intrinsic viscosity, the solvent chosen was poor. The difference in structure between the linear polymers (aliphatic present and thiol end groups) and the starshaped molecules (aromatics and phenol end groups) may also account for the discrepancy between the GPC molecular weights and the calculated viscosity molecular weights. Minor differences in structure between the two series of star-shaped molecules were found to have a profound influence on the Mark-Houwink constants. The use of star-shaped molecules as calibrant via the inherent viscosity for the viscometer was also noted to have over estimated the molecular weight by approximately one third when compared to previously reported linear polymers with GPC data.193 However, the use of dissimilar calibrants in the determination of molecular weights via GPC has also been previously reported to cause errors.164 In order to determine the molecular weights of the prepared hyperbranched polymers, the intrinsic viscosities were calculated using the Huggins, Kramer and Fuoss  114  plots and equations. In general, the polymers displayed higher intrinsic viscosities than the star-shaped molecules. The hyperbranched polymers removed just prior to the gel point displayed characteristically high viscosities. As per the linear and star-shaped molecules, the intrinsic viscosities calculated by three methods were not the same suggesting that the solvent choice was poor. Calculation of the Huggins and Kramer constants as well as their product allows for the deduction that these polymers assume a spherical shape in solution. Confirmation of the spherical nature requires independent assessment of molecular weight. Table 3.25 Intrinsic viscosity values and constants as calculated for the Huggins, Kramer and Fuoss equations [η] kH [η] kK kH + k K [η] B Huggins Kramer Fuoss  4.1b 4.2b 4.3 4.4 4.6b 4.7 4.8 4.9 4.10 4.11b 4.12  28.77 21.94 26.17 24.32 36.13 23.57 766.30 557.46 97.88 36.39 21.49  -1.57 -1.54 -1.49 -1.14 -0.78 -0.38 0.09 0.66 -0.29 -0.67 -0.77  28.66 21.65 25.56 23.64 34.52 23.16 603.64 570.40 94.06 34.31 21.02  1.90 1.76 1.26 1.34 0.96 0.69 0.14 0.03 0.54 0.85 1.01  0.33 0.22 -0.23 0.20 0.18 0.31 0.23 0.69 0.25 0.17 0.25  49.26 14.39 52.08 30.86 68.49 38.02 909.09 526.32 196.08 119.05 60.24  20.03 -1.72 17.58 6.58 16.82 8.39 -0.45 -10.05 20.33 33.77 24.42  Calculation of molecular weights of the hyperbranched polymers (chapter 4) was accomplished using k and α from both figures 3.15 (star-shaped) and 3.18 (linear) as well as the calibration graph (figure 3.22). The α value for hyperbranched polymers in an ideal solvent is 0.4. In the chosen solvent, this value may be expected to decrease based upon the increased spherical nature of the star-shaped molecules with organic end groups and that the solvent has been previously shown to not be ideal. When the molecular weights are assumed to act similarly to the star-shaped molecules (figure 3.15), the estimated molecular 115  weights are above those calculated by the calibration curve (figure 3.22) as seen in table 3.26. The molecular weights for hyperbranched polymers 4.8 and 4.9 are improbably high due to near gelation of the polymerization reaction. If the hyperbranched polymers were expected to act more like the prepared linear polymers (figure 3.18), the molecular weight calculated were lower than expected and in some cases, improbable. Attempts at using the Mark-Houwink  constants  derived  from  the  Fuoss  equation  also  resulted  in  improbable/impossible numbers. For each hyperbranched polymer, molecular weights were found using the calibration graph equation which was then scaled to previously reported polymers. Confirmation of these molecular weights using GPC was not possible due to irreversible interactions between the column gel and the iron. Table 3.26 Molecular weights of the hyperbranched polymers from the calibration curve and the Mark-Houwink equations (M-H) using the constants derived from the Huggins equation Star M-H Linear M-H ηinh at Un-scaled Scaled MW MW (g/mol) MW (g/mol) [0.005g/mL] MW (g/mol) (g/mol) 37 900 12 300 20.87 40 400 26 900 4.1b 12 000 35 100 17.52 23 000 15 300 4.2b 25 400 17 700 21.44 43 400 28 900 4.3 18 600 23 600 19.89 35 300 23 500 4.4 99 400 5 100 28.82 81 700 54 500 4.6b 16 300 26 600 21.30 42 600 28 400 4.7 4.11 x 1010 27 349.47 1 747 400 1 164 900 4.8 1.07 x 1010 8 616.99 3 137 100 2 091 400 4.9 6 764 800 107 70.36 297 500 198 300 4.10 102 500 4 900 29.33 84 300 56 200 4.11b 11 000 38 100 18.78 29 600 19 700 4.12  3.3 Conclusions Star-shaped molecules containing ether or ether/ester linkages were prepared to give stars with up to 15 metallic moieties. A single branch point was also introduced to the starshaped molecules. The introduction of the ester linkage was found to decrease the thermal  116  stability of the molecules backbone by approximately 100 oC whereas the branch point was found to increase the thermal stability of the backbone by only 20 oC. The glass transition temperature was found to vary with size and linkage type. Viscosity measurements illustrated the polyelectrolyte effect that is consistent with the presence of the cationic iron. Various viscometric parameters were calculated and the general size and shape of the starshaped molecules was determined.  3.4 Experimental 3.4.1 Materials Phloroglucinol (3.19, Fluka), hydroquinone (3.3), 4-hydroxybenzoic acid (2.2), 2allylphenol (3.1), 4,4-bis(4-hydroxyphenyl)valeric acid (3.22), 4-dimethylaminopyridine (DMAP), and dicyclohexylcarbodiimide (DCC, Aldrich Chemical Co.) were used as received without purification. All solvents were HPLC grade and used without purification omitting THF, which was distilled over benzophenone/sodium prior to use. Compounds  1.37a,b, 2.1, 3.10, 3.11 and 3.23a were prepared according to previously established methodologies.121,125,133,137,151,227  3.4.2 Characterization 1  H and  13  C NMR spectra were collected at 200 and 50 MHz, respectively using a  Gemini 200 NMR spectrophotometer. Solvent residues were used to reference and chemical shifts were calculated ppm whereas J coupling was calculated in hertz (Hz). Thermogravimetric analysis (TGA) was performed using a Mettler TGA/SDTA851e at a heating rate of 20 oC/min under a flow of nitrogen. Differential Scanning Calorimetry (DSC) was performed with a Mettler 821e with a heating rate of 20 oC/min under a flow of nitrogen. Viscometry was measured with a Brookfield DV II+ viscometer at 100 rpm with  117  a UL adapter set to 25.0 oC in DMSO. Inherent viscosity was calculated from the linear portion of the curve using the equation of the line and a concentration of 0.5 dL/g.  3.4.3 Procedures 3.4.3.1 Synthesis of 3.2, 3.5, 3.7, 3.9 In a 50 mL round bottom covered from light, the dichlorocomplex was reacted with the appropriate 2-allylphenol derivative in a 1:1 ratio in the presence of excess potassium carbonate. The reaction mixture was stirred in DMF for 16 hours under nitrogen atmosphere. The product was poured into 10% HCl followed by addition of NH4PF6. The resultant solid product was filtered and left to dry under reduced pressure in the dark.  3.4.3.2 Synthesis of 3.4, 3.6, 3.8 Excess hydroquinone (3.3), excess potassium carbonate, the appropriate chloroarene derivative and DMF were stirred in a 50 mL round bottom flask covered from light under a nitrogen atmosphere for 16 hours. The product was then isolated by pouring the reaction mixture into 10% HCl, followed by the addition of NH4PF6. The solid product was filtered and dried under reduced pressure in the dark.  3.4.3.3 Synthesis of 3.12-3.16 The appropriate substituted chloroarene complexes were reacted with the central phenolic core in a 3.3:1.0 ratio in the presence of excess potassium carbonate and a solvent of DMF. After the mixture had stirred for 16 hours in the dark under a nitrogen atmosphere, the star-shaped molecule was isolated by precipitation in 10% HCl and NH4PF6 was added. The solid was filtered and dried under reduced pressure in the dark. If purification from the mono- and di-substituted products was required, this was conducted by column chromatography using activated neutral alumina as the solid phase and  118  appropriate solvent as the mobile phase. Collection of the first coloured band resulted in the pure product.  3.4.3.4 Synthesis of 3.17, 3.18 The appropriate chloroarene complex was stirred under nitrogen atmosphere in the dark with a large excess of 4-hydroxybenzoic acid (2.2), an excess of potassium carbonate at 60 oC in a 1:1 mixture of DMF and THF. The product was isolated by precipitation into 10% HCl followed by the addition of NH4PF6 and then extracted with dichloromethane. After washing the organic layer with water and drying with magnesium sulphate, the organic layer was filtered and evaporated. The residue was dissolved in acetone and precipitated into diethyl ether. The solid product was filtered and dried in the dark under reduced pressure.  3.4.3.5 Synthesis of 3.20, 3.21, 3.24 The appropriate carboxylic acid containing arm was combined in a 3:1 ratio with either phenolic core in the presence of excess DMAP, 2mL of DMSO and 5mL of DCM. After 5 min of reaction under nitrogen atmosphere and excess of DCC was added to the reaction mixture. This mixture was stirred, under nitrogen, in the dark for 3 days at room temperature. The product was poured into 10% HCl, followed by addition of NH4PF6 and quickly extracted into DCM. The organic layer was washed with water causing precipitation of the product. The product was then dissolved in DMF, reprecipitated into 10% HCl, followed again by the addition of NH4PF6 and the solid was immediately filtered. Purification, if necessary was achieved in the same manner as for the allyl-capped star-shaped molecules.  119  3.4.3.6 Synthesis of 3.23a,b The chloroarene complex was reacted with 4,4-bis(4-hydroxyphenyl)valeric acid (3.22) in a 2:1 ratio at 60 oC under a nitrogen atmosphere, in the dark with excess potassium carbonate for 16 hours. The bimetallic complex was isolated by precipitation into 10% HCl followed by the addition of NH4PF6. The product was then extracted with DCM, washed with water, dried with magnesium sulphate, filtered and the solvent evaporated. The residue was washed with basic water, dissolved in acetone and poured into 10% HCl with the addition of NH4PF6. The solid product was filtered and dried under reduced pressure in the dark.  120  4 Hyperbranched polymers containing cyclopentadienyliron 4.1 Introduction Hyperbranched polymers are those polymers that are highly branched with irregular structures. They are formed by ‘one-pot’ synthesis between two different functional groups that may be present on a single monomer or on two or more different monomers. The ‘onepot’ synthesis is preferred over dendrimer/star-shaped molecules for large scale applications due to the ease of synthesis. This method gives rise, most commonly to ABx hyperbranched polymers130,246-262 (x is usually 2) and A2 + B3 hyperbranched polymers,263279  although other varieties have been published.280-304 AB2 polymers are preferred as they  do not result in network formation like A2 + B3 polymers. Very few AB2 monomers are, however, available commercially, unlike A2 + B3 monomers which are readily available. The majority of hyperbranched polymers to date are organic in nature. Some metalled examples have been prepared containing iron270-273,299 or other transition metals.261,282,301 Ferrocene containing hyperbranched polymers have been prepared in 30-100 % yields by cyclotrimerization and the A2 + B3 methodology.270-272,299 Molecular weights of these ferrocene containing hyperbranched polymers have been reported to range between 800 g/mol and 135 000 g/mol based upon GPC in THF relative to linear polystyrene calibration. Glass transition temperatures were found in the range of –70 to +105 oC. When the glass transition temperature was found below 0 oC, a melting point of 30-40 degrees higher than the glass transition was found. Decomposition of the hyperbranched polymers did not occur until above 270 oC.270-272,299 The glass transition temperature has been found theoretically to vary with the formation of the hyperbranched polymer.305 The glass transition temperature will increase at a rate matching an increase in the reciprocal of the  121  molecular weight and it will decrease with an increase in the amount of branching/formation of dendritic units in the polymer.305 Within this chapter, several polymers and some networks prepared by the ‘one-pot’ synthesis of A2 + B3 monomers will be presented. The influence of method of synthesis and choice of starting materials will be related to the thermal properties of the resultant products. Differentiation between network formation and hyperbranched polymer formation was determined using solubilities and NMR. Thermal properties were tested by TGA and DSC. Molecular weights of the soluble materials were found by viscosity via comparison to star-shaped molecules of known molecular weights.  4.2 Results and discussion 4.2.1 Synthesis and properties of hyperbranched polymers based upon phloroglucinol Hyperbranched polymers were prepared with a small B3 or star-shaped core unit as seen in scheme 4.1. For these, the commercially available phloroglucinol was combined with a bi-functional η6-arene-η5-cyclopentadienyliron A2 unit. The A2 monomers used were those of η6-p-dichlorobenzene-η5-cyclopentadienyliron (2.1) and a di-substituted valeric acid (1.33). The valeric acid derivative was chosen as it has been reported in literature to reduce the amount of intramolecular cyclization during the polymerization reaction thereby leading to a decreased likelihood of network formation. The reaction was carried out using either a 3:2 stoichiometric ratio of A2 to B3 or a 1:1 ratio of A2 to B3 to see if there was an influence in the properties of the resultant polymer. The influence of heat on the synthesis was also examined in the hope of producing larger polymers by forcing the reaction.  122  Hyperbranched Polymer 4.1 a, b 4.2 a, b a, 1:1 molar ratio b, 3:2 molar ratio Cl M  Room Temperature Cl 2.1 =  OH 2.1  O  M  Cl  or HO  O  1.33  OH  1.33 =  3.19 B3  HO  60 oC  O  M = Fe+Cp A2  Hyperbranched Polymer 4.3 4.4  M Cl  Scheme 4.1 As can be seen in the 1H NMR spectra (figure 4.1) of polymer 4.1b and in table 4.1, multiplication of the proton resonances is present. This is characteristic of hyperbranched polymers. The phenolic proton corresponding to phloroglucinol in the linear and terminal positions appeared as a broad singlet at 10.68 ppm. The cyclopentadienyl group corresponding to the terminal complexes was visible at 5.22 ppm. When the complex was in a linear position, the cyclopentadienyl protons shifted to 5.26 ppm. The remaining cyclopentadienyl protons found at 5.16 ppm were by default assigned to the branched position. These assignments were based upon comparison with previously prepared complexes in which either one or both of the chloro-groups had been substituted by nucleophilic oxygen. Within the multiplet between 6.20-6.81 ppm, both the complexed aromatics and the aromatic protons may be found. Due to overlap between the peak multiplications, exact identification of the resonances cannot be assigned. The peak around  123  3 ppm corresponds to water present in the NMR solvent whereas the residual DMSO was present at 2.49 ppm. Table 4.1 1H NMR values and yields for 4.1-4.4 in DMSO-d6 (at 200 MHz) Yield Aliphatics, Alcohol  4.1a  80  9.81 (s, OH)  4.1b  62  10.68 (br s, OH)  4.3  93  10.71 (s, OH)  4.2a  72  4.2b  80  4.4  98  1.65 (br s, CH3), 2.07 (br s, CH2), 2.38 (br s, CH2), 9.29 (br s, OH), 9.80 (br s, OH) 1.65 (br s, CH3), 2.03 (br s, CH2), 2.39 (br s, CH2), 9.38 (s, OH), 9.92 (s, OH), 10.83 (s, OH), 12.18 (s, COOH) 1.65 (br s, CH3), 2.06 (br s, CH2), 2.41 (br s, CH2), 9.85 (br s, OH), 12.14 (br s, COOH)  Cp  Complexed Aromatic 5.19 (s), 6.07-6.84 (br m) 5.21 (s), 5.26 (s) 5.16 (s), 6.20-6.81 (br m) 5.22 (s), 5.26 (s) 5.05 (s), 6.02-6.65 (br m) 5.22 (s) 5.19 (s), 6.25 (s), 6.41 (d, 5.20 (s), J = 5.1 H), 6.80 5.21 (s), (d, J = 4.7 Hz) 5.26 (s) 5.20 (s), 6.26 (s), 6.41 (s), 5.23 (s), 6,76 (d, J = 14.5 5.27 (s) Hz)  Aromatics 6.07-6.84 (br m)  6.20-6.81 (br m)  6.02-6.65 (br m) 6.07 (s), 7.15 (s), 7.26 (br s), 7.34 (br s) 6.12 (s), 6.99 (s), 7.26 (s), 7.33 (s)  5.04 (s), 6.19 (s), 6.41 (s), 6.10 (s), 7.00 (s), 5.20 (s), 6.74 (d, J = 17.6 7.25 (s), 7.33 (s) 5.22 (s), Hz) 5.27 (s)  Figure 4.1 1H NMR spectrum of 4.1b in DMSO-d6 (at 200 MHz)  124  The  13  C NMR spectrum also displays resonance multiplication due to the presence  of dendritic, linear and terminal units as seen in table 4.2 and figure 4.2 of polymer 4.3. For example, with phloroglucinol, these may be seen at 103.03, 105.06 and 110.51 ppm. In comparison with star-shaped molecules and with linear polymers, it may be deduced that the resonance at 103.01 ppm is due to the linear A3 units, the 105.06 ppm resonances are due to the terminal A3 units and the 110.51 ppm peak is due to the dendritic units. The cyclopentadienyl carbons appeared at 77.06 and 77.96 ppm, corresponding to the linear and the terminal positions respectively. The quaternary aromatics appeared at 127.59, 129.61, 155.52, 156.33 and 160.72 ppm. The complexed aromatics appeared at 72.83, 75.49 and 86.70 ppm. These relate to the near the oxygen in both the linear and terminal positions and the aromatic carbon next to the chlorine substituted carbon. The strong resonance at 39.5 ppm corresponded to the residual DMSO in the deuterated solvent.  Figure 4.2 13C APT NMR of 4.3 in DMSO-d6 (at 200 MHz)  125  Table 4.2 13C NMR values for 4.1-4.4 in DMSO-d6 (200 MHz unless denoted by † then at 300 MHz)(quaternary carbons denoted by *) Aliphatics, C=O Cp Complexed Aromatics † 77.93 74.86, 79.08, 103.42*, 106.18, 155.41*, 159.89*, 4.1a 130.31* 161.10* 77.85, 75.35, 76.40, 86.58, 103.01, 105.05, 105.45, 4.1b 79.21 103.56*, 129.52* 131.46*, 154.70*, 155.36*, 160.72* 77.06, 72.83, 75.49, 86.70, 103.03, 105.06, 110.51, 4.3 77.96 127.59*, 129.61* 155.52*, 156.33*, 160.72* (CH3), 77.28, 74.48, 74.87, 75.18, 114.85, 119.85, 121.15, 4.2a† 26.92 29.65 (CH2), 77.72, 75.57, 86.71, 103.50*, 129.79, 130.16, 131.91, 45.00 (CH2), 78.15, 127.83*, 137.91* 145.99*, 146.44*, 150.97*, 174.17 (C=O) 78.83, 151.59*, 154.61*, 155.25*, 79.19 159.84* 26.90 (CH3), 77.84, 74.42, 74.96, 75.41, 98.42, 100.53, 105.21, 4.2b 29.74 (CH2), 79.25 76.41, 76.18, 86.72, 114.84, 119.84, 120.08, 103.39*, 129.73*, 129.50, 131.87*, 145.90*, 36.02 (CH2), 44.85 (CH2), 129.95*, 130.14* 146.37*, 150.80*, 151.42*, 159.81 (C=O), 154.31*, 155.33* 160.78 (C=O), 174.18 (C=O) 26.93 (CH3), 77.89, 74.45, 75.02, 75.55, 98.50, 100.64, 105.24, 4.4 29.82 (CH2), 79.30 76.23, 86.76, 103.48*, 119.91, 120.13, 129.25, 130.23* 131.96*, 146.07*, 146.35*, 44.95 (CH2), 159.89 (C=O), 150.98*, 151.52*, 154.42*, 160.87 (C=O), 155.44* 174.30 (C=O)  As may be seen in table 4.3, the hyperbranched polymers prepared displayed unusual thermal properties. By this, it is meant that the polymers displayed, when prepared at elevated temperatures, two phase transitions. This has previously been reported for ferrocene hyperbranched polymers270,272 but has not been reported for any η6-arene-η5cyclopentadienyliron based compounds. The first phase transition may be attributed to that of a glass transition (Tg) whereas the second transition was attributed to a melting (Tm). The range of the phase transitions is reasonable based upon the large amount of branching present in the backbone of the polyether polymers, as it was seen that introduction of a  126  single branch point into a polyether backbone brought the glass transition temperature to below that of the decomposition temperature (first weight loss, ca. 230 oC). The relative spacing between that of the glass transition and the melting point is reasonable based upon comparison related ferrocene hyperbranched polymers.270,272 A second explanation, although less plausible as it has not been previously reported in literature, is that of the compounds having two glass transitions. One transition could be that of the external regions of the hyperbranched polymers, which would be more flexible, and the second transition corresponding to a glass transition in the inner regions or a cyclic region of the hyperbranched polymer which would be less flexible. Further testing of the phase transitions and the polymers would be required to rule out this possibility. Table 4.3 Thermal analysis for 4.1b, 4.2b, 4.3, 4.4 Tg Tm Weight Tonset Tendset Weight Loss (oC) (oC) Loss (%) (%) 239 269 14 4.1b 108 190 26 236 269 15 4.3 115 180 26  4.2b 4.4 86  165 19 177 19  230 235  262 266  25 23  Tonset Tendset Weight Tonset (oC) (oC) (oC) Loss (%) 452 524 11 889 465 528 5 830 6 881 419 523 20 878 418 507 14 883  Tendset (oC) 921 851 893 925 929  The thermal stability of the polymers did not appear to be overly different that related star-shaped molecules or linear polyether polymers. The cleavage of the cyclopentadienyliron moiety was noted to occur between 230 to 270 oC for the four polymers. It may be noted that by changing the A2 monomer, the amount of polymer backbone lost corresponded to the percentage of A2 monomer in the polymer. The degradation of the polymeric backbone began to occur around 420 oC for the aliphatic containing compounds and 450 oC for the non-aliphatic compounds. A final weight loss  127  was noted above 875 oC. This corresponds to breakdown of the degradation products. The synthesis conditions apparently did not affect the thermal stability of these polymers. Molecular weights of the hyperbranched polymers were determined by viscosity (table 4.4). Due to the interaction of the η5-cyclopentadienyliron moieties interaction with gel permeation chromatography (GPC) columns the polymers were not tested by GPC. Standards for viscosity were prepared using the star-shaped molecules previously prepared and all samples were run under the same conditions. Discussion of the calibration may be found in chapter 3, section 3.2.5. The lowest viscosities and molecular weights were noted with the polymers prepared at room temperature. This was to be expected since elevated temperature has been previously shown to force the reaction thereby increasing molecular weights. When the valeric acid derived A2 unit (3.25a) was used, a decrease in molecular weights were noted over those of the dichlorocomplex A2 unit (2.1). This may be related to a decrease in intramolecular cyclization as previously reported in literature or decreased reactivity of the valeric acid derivative due to hydrogen bonding with the B3 core. Table 4.4 Inherent viscosity and molecular weights of 4.1b, 4.2b, 4.3, 4.4 Compound Inherent Viscosity (L/g) Molecular Weight (g/mol) 0.209 25 500 4.1b 0.214 27 500 4.3 0.175 12 200 4.2b 0.199 21 600 4.4  Degree branching calculations were carried out for 4.1a, 4.1b and 4.3 using equations 1.1 and 1.2. Values for the relative amounts of linear, terminal and dendrimeric units were estimated from the relative intensities in the NMR spectra. Compound 4.1a gave a value of 0.64, compound 4.1b a value of 0.67 and compound 4.3 a degree branching of 0.69. Based upon these values it may be seen that the stoichiometric ratio for the synthesis  128  of a hyperbranched polymer when prepared at room temperature leads to the ideal degree branching of 0.67, where as the addition of heat forces the reaction to give an increased number of dendritic units and a non-ideal stoichiometric ratio gives a degree branching closer to that of a linear polymer.  4.2.2 Synthesis and properties of hyperbranched polymers based upon chlorostar Hyperbranched polymers were prepared based upon the chloro-capped star-shaped molecule as seen in scheme 4.2. This chloro-capped star (3.10, B3) was reacted with various commercially available dinucleophiles (A2) to give hyperbranched polymers and networks. It was found that when using the 3:2 stoichiometric ratio between A2 and B3 and room temperature conditions that network formation occurred instead of hyperbranched polymer formation. This may be due to intramolecular cyclization, as the valeric acid derivative did not gelate under the same conditions. When the 3:2 stiochiometric ratio was used at elevated temperatures, hyperbranched polymer formation was found to occur instead of network formation or gelation.  129  Hyperbranched Polymer/Gelation a, 1:1 molar ratio 4.6 a, b, c b, 3:2 molar ratio 4.7, 4.8, 4.9 c, gelation product Cl Room Temperature M  O Cl  O  O  M  M=Fe+PF6-Cp  3.3, X = O, Ar =  Ar HX  M  XH  HO  O  3.10 3.22, X = O, Ar =  Cl 4.5, X = O, Ar = S  60 oC 2.8, X = S, Ar =  Hyperbranched Polymer 4.10  Scheme 4.2 The 1H NMR shifts may be seen in table 4.5 and an example spectrum of polymer  4.6b found in figure 4.3. In this figure, it may be seen that multiplication of the proton resonances has occurred. The cyclopentadienyl hydrogens may be found at 5.22 and 5.27 ppm,  corresponding  to  the  di-substituted  and  mono-substituted  η6-arene-η5-  cyclopentadienyl complexes. The complexed aromatics thus were found at 6.18, 6.37, and 6.59 ppm. The peaks at 6.18 (d, J = 5.9 Hz) and 6.59 are related to the di-substituted complex whereas the mono-substituted complex was found at 6.37 ppm. Doublets were found for the terminal hydroquinone at 6.89 ppm (J = 9.0 Hz) and at 7.11 ppm (J = 8.4 Hz). A singlet resonating at 7.32 ppm was assigned to the central uncomplexed proton from the A3 unit. A doublet at 7.43 ppm with coupling of 11.3 hertz was attributed to the hydroquinone in the linear position. The final proton was found at 9.77 ppm and  130  corresponds to the phenolic proton from the terminal hydroquinone (B2). Water present in the NMR solvent is visible around 3.5 ppm, residual DMF from polymerization between 2.5-3 ppm and residual DMSO in the deuterated solvent appeared at 2.49 ppm. Table 4.5 1H NMR and yields for 4.6-4.10 in DMSO-d6 (200 MHz unless denoted by †, then 300 MHz) Yield Aliphatic, OH Cp Complexed Aromatic 64 5.27 (s), 6.60 (d, J = 8.0 Hz), 7.41 (d, J = 4.6a 5.29 (s) 6.72 (s), 6.88 (d, J = 4.3 Hz) 6.3 Hz) 9.77 (br s, OH) 5.22 (s), 6.18 (d, J = 5.9 Hz), 6.89 (d, J = 4.6b 68 5.27 (s) 6.37 (br s), 6.59 (br 9.0 Hz), 7.11 s) (d, J = 8.4 Hz), 7.32 (s), 7.43 (d, J = 11.3 Hz) 4.67 (br 6.50 (d, J = 16.4 7.01 (br s) 4.6c 92 s), 5.22 Hz) (br s) 1.44 (s, CH3), 1.92 (s, 5.26 (br 6.65 (br s) 6.91 (br s), 4.7† 71 CH2), 2.20 (s, CH2) s), 5.33 7.52 (br s) (br s) 97 1.61 (br s, CH3), 1.68 5.22 (s) 6.28 (br s), 6.52 (br 7.19 (br s), 4.8 (br s CH3), 9.25 (s, s) 7.37 (br s) OH) 74 5.16 (s) 6.32 (br s), 6.68 (br 7.45 (br s), 4.9 s) 7.61 (br s) 9.38 (br s, OH), 9.78 4.08 (s), 6.28 (br s), 6.33 (br 6.66 (br s), 4.10 64 (br s, OH), 10.23 (br 4.55 (s), s) 6.96 (br s), s, OH), 10.68 (br s, 5.03 (s), 7.12 (br s) OH), 11.40 (br s, 5.08 (s), OH) 5.17 (s)  131  Figure 4.3 1H NMR spectrum of 4.6b in DMSO-d6 (at 200 MHz) The  13  C NMR confirms the peak multiplication found in the 1H NMR that is  consistent with hyperbranched polymer formation (figure 4.4 of polymer 4.6b, table 4.6). Namely, both the linear and terminal B3 cyclopentadienyl carbons were found at 77.78 and 78.05 ppm. The complexed aromatics were found at 73.57, 74.88, and 75.92 ppm with quaternary complexed aromatics at 128.83 and 144.63 ppm. The uncomplexed aromatics were found to resonate at 109.90, 116.81, 121.97, and 122.81 ppm. The central aromatic CH of the B3 unit corresponded to the 109.90 resonance whereas the remaining three are related to the hydroquinone A2 unit in the linear and terminal positions. The quaternary aromatics were found to resonate at 129.25, 130.45, 131.92, 150.88, 155.76, and 156.47 ppm. Residual DMSO in the deuterated solvent appeared as the strong peak at 39.9 ppm, whereas the peak at 99 ppm was found to have no area under it.  132  Table 4.6 13C NMR values for 4.6-4.10 in DMSO-d6 (200 MHz unless †, then at 300 MHz, 13 C run at 600 MHz as solid state with MAS)(* denotes quaternary carbons) Other Cp Complexed Aromatics † 79.21 76.91, 86.58, 110.67, 130.91, 155.74* 4.6a 103.97* 77.78, 73.57, 74.88, 75.92, 109.90, 116.81, 121.97, 122.81, 4.6b 78.05 128.83*, 144.63* 129.25*, 130.45*, 131.92*, 150.88*, 155.76*, 156.47* 80 80, 153* 132, 158*, 168* 4.6c † 76.89, 86.70, 111.96, 114.58, 127.66, 27.14 (CH3), 79.42 4.7 103.94*, 131.79* 139.25*, 154.91*, 155.69* 29.90 (CH2), 43.86 (CH2), 174.61 (C=O) 30.56 (CH3), 77.92 74.77, 75.91, 79.37, 99.32, 100.53, 101.77, 103.20, 4.8 30.65 (CH3) 130.58* 110.24, 114.71, 119.89, 120.00, 127.30, 128.72, 147.75*, 148.85*, 151.17*, 156.27* 78.66 76.88, 84.94, 128.24, 132.02, 135.01, 4.9 131.29*, 148.14* 136.29*, 155.63* 76.45, 69.25, 72.32, 73.06, 99.92, 101.90, 103.40, 115.71, 4.10 77.32 74.03, 81.31, 116.24, 119.51, 120.04, 120.97, 128.82*, 128.89*, 121.46, 130.11*, 131.11*, 144.11* 147.83*, 149.90*, 150.44*, 151.83*, 152.91*, 154.28*, 155.19*, 159.64*  Figure 4.4 13C APT NMR of 4.6b in DMSO-d6 (at 200 MHz)  133  Thermal analysis of the hyperbranched polymers and networks may be seen in table 4.7. As with the hyperbranched polymers using phloroglucinol as the B3 unit, the chlorocapped star B3 unit compounds also displayed two phase transitions. The polymer network that was allowed to gelate completely (4.6) was seen to have the lowest phase transition and highest thermal stability. Glass transition temperatures were detected in all but one of the hyperbranched polymers/networks and ranged from 60 to 105 oC. The second phase transition was found to range between 155 and 190 oC and was found in all of the compounds prepared from the chloro-capped star-shaped molecule as the B3 monomer. Table 4.7 Thermal analysis for 4.6a,b, 4.7-4.10 Tg Tm Weight Tonset Tendset Weight Loss (oC) (oC) Loss (%) (%) 103 178 31 247 272 17 4.6b 232 261 13 4.6c 60 155 11 211 284 14 4.7 100 170 39 178 29 255 278 21 4.8 252 269 19 4.9 91 189 29 237 262 23 4.10 77 169 21  Tonset Tendset Weight Tonset (oC) (oC) (oC) Loss (%) 433 531 8 827 567 594 24 871 415 444 486 527 12 780 484 560 448 532 11 841  Tendset (oC) 870 938 859 895  The first loss of thermal stability was found to occur between 210-285 oC as expected for the cleavage of the η5-cyclopentadienyliron moiety. Breakdown of the polyether backbone was found to occur above 415 oC with the highest initial breakdown temperature belonging to the gelation product at 565 oC (figure 4.5). The use of a valeric acid derivative as the A2 monomer caused a decrease in thermal stability in relation to the remains of the polymers with thermal breakdown occurring at lower temperatures and with a larger amount lost in the initial weight loss.  134  Figure 4.5 TGA thermogram of 3.21, 4.6c, 4.10, 4.6b from top to bottom The molecular weights of the hyperbranched polymers and networks prepared from the chloro-capped star-shape molecule as well as the inherent viscosities used to calculate these may be found in table 4.8. In this, it may be easily seen that the formation of networks could be quickly detected based upon the viscosity. These networks, although still highly soluble as expected for the hyperbranched polymers were extremely viscous. Discussion of these viscosity values may be found in section 3.2.5 in chapter 3. Molecular weights by GPC were not able to be determined due to inhibitory interactions between the column and the iron moiety, thus confirmation of the weights derived from the standardized viscosity readings were not possible. Table 4.8 Inherent viscosity and molecular weights of 4.6b, 4.7-4.10 Inherent Viscosity (L/g) Molecular Weight (g/mol) 0.288 56 500 4.6b 0.213 25 100 4.7 3.495 216 000 4.8 5.210 390 000 4.9 0.704 119 900 4.10  135  4.2.3 Synthesis and properties of hyperbranched polymers based upon alcohol star Preparation of hyperbranched polymers using the previously prepared alcoholcapped star-shaped molecule (3.11) as the B3 monomer was accomplished using the pdichlorocompex (2.1) as the A2 monomer as seen in scheme 4.3. Two different temperature regimes were used for synthesis, namely room temperature and elevated at 60 oC. The polymers were tested using NMR spectroscopy, thermal analysis and viscometry. OH  Hyperbranched Polymer 4.11 a, b a, 1:1 molar ratio b, 3:2 molar ratio  O  Room Temperature M  O O M  O  M  2.1  O  OH  3.11 M=Fe+PF6-Cp  60 oC  O Hyperbranched Polymer HO  4.12  Scheme 4.3 Proton shifts may be found in table 4.9 and a representative spectrum found of polymer 4.11b in figure 4.6. For example, the cyclopentadienyl protons resonated at 5.18, 5.21, 5.26 and 5.30 ppm. Based upon previously discussed similar compounds, the peaks at  136  5.21 and 5.26 ppm may be assigned to linear and terminal cyclopentadienyl protons from the B3 unit, respectively. The 5.18 and 5.30 ppm resonances may then be assigned to the A2 cyclopentadienyl protons in the linear and terminal positions respectively. The complexed aromatics appeared as three broad singlets at 6.20, 6.34 and 6.53 ppm. The central singlet at 6.34 ppm was attributed to the B3 complexed aromatic whereas the remaining two were assigned to the A2 complexed aromatics in the linear and terminal positions. Doublets at 6.89 ppm (J = 10.0 Hz) and 7.11 ppm (J = 9.8 Hz) correspond to the phenolic aromatic from the B3 unit. The phenolic proton appeared at 9.74 ppm. The broad singlets at 7.33 and 7.47 ppm were assigned to the aromatics from the B3 unit upon reaction with the A2 complex. When the A2 complex was terminal, the aromatic appeared at 7.33 ppm and when it was linear, the resonance shifted to 7.47 ppm. The remaining singlet resonating at 7.59 ppm was that of the central aromatic proton in the B3 unit. Peaks between 2.5-3.5 ppm and approximately 8 ppm corresponded to water and DMF present in the sample. Residual DMSO in the deuterated solvent appeared at 2.49 ppm whereas the peak at 2.04 ppm was due to residual acetone in the NMR tube. Table 4.9 1H NMR values and yields for 4.11, 4.12 in DMSO-d6 (200 MHz) Yield 4.11a 89  4.11b 98  4.12  98  Cp 5.15 (s), 5.18 (s), 5.20 (s), 5.24 (s), 5.25 (s), 5.29 (s), 5.30 (s) 5.18 (s), 5.21 (s), 5.26 (s), 5.30 (s)  Complexed 6.17-6.48 (m)  Aromatics 6.89 (d, J = 8.6 Hz), 7.11 (d, J = 8.6 Hz), 7.27 (d, J = 3.5 Hz), 7.33 (s), 7.47 (s), 7.59(s) 6.20 (br s), 6.34 6.89 (d, J = 10.0 Hz), (br s), 6.53 (br 7.11 (d, J = 9.8 Hz), 7.33 s) (br s), 7.47 (br s), 7.59 (br s) 5.07 (s), 5.18 (s), 6.06-6.64 (br s) 6.91 (br s), 7.13 (br s), 5.19 (s), 5.21 (br 7.38 (br s), 7.45 (br s), s), 5.28 (br s) 7.62 (br s)  OH 9.75 (s)  9.74 (s)  9.76 (s)  137  Figure 4.6 1H NMR spectrum of 4.11b in DMSO-d6 (at 200 MHz) Analysis of the 13C NMR for the hyperbranched polymers using the alcohol star as the B3 unit was complicated due to overlap and collapse of various carbon resonances associated with the presence of multiple types of η6-arene-η5-cyclopentadienyliron complexes. This analysis may be found in table 4.10 with polymer 4.11b shown in figure 4.7. Several cyclopentadienyl carbons were found at 77.59, 77.81 and 78.02 ppm with the complexed aromatics appearing at 73.79, 74.82, 76.00 and 76.90 ppm. The uncomplexed aromatics resonated at 109.44, 112.54, 116.79, 121.96, 122.79 and 124.66 ppm, where the 109.44 resonances corresponded to the central aromatic carbon of the B3 unit. The quaternary carbons were found at 128.66, 129.06, 130.19, 130.75, 131.95, 132.37, 144.64, 150.82, 150.96, 151.62, 155.19, 155.68 and 156.40 ppm. Residual DMSO in the deuterated solvent was found at 39.5 ppm. DMF and alcohol account for the peaks in the aliphatic region whereas the peak at 99 ppm was found to have no area.  138  Table 4.10 13C NMR for 4.11, 4.12 in DMSO-d6 (200 MHz)(* denotes quaternary carbons) Cp Complexed Aromatic 73.23, 73.79, 74.45, 74.95, 112.54, 116.80, 121.98, 122.76, 4.11a 77.58, 77.80, 76.00, 127.65*, 128.60*, 124.83, 131.93*, 132.07*, 77.92, 130.84* 132.35*, 144.62*, 150.81*, 78.21 151.56*, 155.76*, 156.48* 73.79, 74.82, 76.00, 76.90, 109.44, 112.54, 116.79, 121.96, 4.11b 77.59, 77.81, 128.66*, 129.06* 122.79, 124.66, 130.19*, 130.75*, 78.02 131.95*, 132.37*, 144.64*, 150.82*, 150.96*, 151.62*, 155.19*, 155.68*, 156.40* 77.05, 72.80, 73.59, 74.85, 75.42, 102.67, 104.93, 108.01, 109.77, 4.12 77.67, 75.83, 127.73*, 128.54*, 116.81, 121.99, 122.79, 124.87, 77.92 128.88*, 129.09*, 129.56* 130.37*, 131.18*, 131.31*, 131.66*, 131.90*, 132.24*, 144.68*, 150.66*, 150.84*, 151.25*, 154.88, 155.72, 160.67*  Figure 4.7 13C APT NMR of 4.11b in DMSO-d6 (at 200MHz) Table 4.11 displays the thermal analysis of the hyperbranched polymers prepared from the alcohol-capped star-shaped molecule as the B3 monomer. The polymer prepared at room temperature displayed different thermal properties than the structurally analogous polymer prepared at 60 oC. For example, the room temperature polymer had higher  139  degradation temperatures for both the loss of the metal moiety and for the breakdown of the polyether backbone. The glass transition and the melting temperatures for the elevated temperature synthesis were closer together than those for the room temperature synthesis. Table 4.11 Thermal analysis for 4.11b, 4.12 Tg Tm Weight Tonset Tendset Loss (oC) (oC) (%) 257 279 4.11b 81 193 34 238 268 4.12 134 189 28  Weight Loss (%) 18 23  Tonset Tendset Weight Tonset (oC) (oC) (oC) Loss (%) 437 548 5 851 390 485 14 850  Tendset (oC) 866 874  The inherent viscosity and hence the molecular weights show a reversal in the trend of increased temperature leading to increased viscosity and molecular weights as seen in the previously prepared compounds (tables 4.4, 4.8 and 4.12). Discussion of these viscosity values may be found in chapter 3, section 3.2.5. This may be due to cyclization occurring intramolecularly between two of the longer arms of the star-shaped B3 unit. This would lead to a termination step in the reaction by removal of the possibility of linear and dendritic B3 units. Table 4.12 Inherent viscosity and molecular weights for 4.11b, 4.12 Inherent Viscosity (L/g) Molecular Weight (g/mol) 0.293 58 500 4.11b 0.189 17 700 4.12  4.3 Conclusions Polyether hyperbranched polymers and networks may be prepared using η6-areneη5-cyclopentadienyliron moieties in the backbone. By increasing the temperature of the reaction, larger polymers were formed when the B3 unit was small. Increased reaction temperature also preferentially formed hyperbranched polymers over that of networks. Network formation and intermolecular cyclization was found to decrease when derivatives  140  of valeric acid were used. Thermal properties were found to be different than similar linear and star-shaped polyethers. For example, two transitions were noted in the DSC and were ascribed to glass transitions and melting. Thermal degradation was found to have changed little in relation to similar linear and star-shaped polymers with the omission of the networks. Network compounds were found to have much higher temperatures for the breakdown of the polyether backbone.  4.4 Experimental 4.4.1 Characterization Solution phase NMR spectra were run on either a Gemini 200 NMR spectrophotometer at 200 MHz for 1H and 50 MHz for  13  C NMR or on a Bruker Avance  DXP300 NMR spectrophotometer at 300 MHz for 1H and 75 MHz for  13  solution phase samples were referenced using solvent residues. Solid-state  13  C NMR. All C NMR was  run on a Varian Inova 600 using magic-angle spinning (MAS) at 20 kHz with the sample in a 3.2 mm rotor. The solid-state sample shifts were relative to TMS using a secondary external reference of adamantane. All chemical shifts are reported in ppm with J coupling in hertz. Differential scanning calorimetry (DSC) was accomplished using a Mettler 821e with a 20 oC/min heating rate under a nitrogen flow. Thermogravimetric analysis (TGA) was done with a Mettler TGA/SDTA 851e with a 20 oC/min heating rate under a nitrogen flow. Viscosity measurements were performed with a Brookfield Model DV II + Viscometer at a rate of 100 rpm in a UL adapter at 25 oC in dimethylsulphoxide (DMSO). Calculated molecular weights were relative to star-shaped molecules of known molecular weights.  141  4.4.2 Materials η6-arene-η5-cyclopentadienyliron containing complexes were prepared according to previous methodologies.121,125,137,151,227 Phlorogucinol (3.19) was purchased from Fluka. All other chemicals were purchased from Aldrich. Solvents were HPLC grade and used without purification.  4.4.3 Procedures 4.4.3.1 Synthesis of 4.1a, 4.2a, 4.6a, 4.11a 0.5 mmol A2 was mixed with 0.5 mmol B3 in the presence of 2 mmol potassium carbonate (K2CO3) in a 25 mL round bottom flask at room temperature in 5 mL dimethylformamide (DMF). The reaction was allowed to continue for 16 hours under nitrogen atmosphere in the dark. The reaction mixture was then poured into 10% aqueous HCl and ammonium hexafluorophoshate (NH4PF6) was added. The resultant precipitate was collected in by vacuum filtration, washed with water and allowed to dry under reduced pressure in the dark.  4.4.3.2 Synthesis of 4.1b, 4.2b, 4.6b, 4.7-4.9, 4.11b 0.3 mmol A2 and 0.2 mmol B3 were mixed with 1mmol potassium carbonate in 2 mL of DMF in a 25 mL round bottom flask. The reaction mixture was stirred under nitrogen atmosphere in the dark for 16 hours or until the solution became viscous. The product mixture was poured into 10% HCl followed by the addition of ammonium hexafluorophosphate. The resultant solid was filtered, washed with water and allowed to dry under reduced pressure in the dark.  142  4.4.3.3 Synthesis of gelation product (4.6c) The amounts used were as per 4.4.3.2. The solution was allowed to congeal and the gelatinous solid was broken up using a spatula. The solid was filtered and washed with diethyl ether. The solid was allowed to dry under reduced pressure in the dark.  4.4.3.4 Synthesis of 4.3, 4.4, 4.10, 4.12 Using the amounts and procedures for 4.4.3.2 with the modification in that the reaction was conducted at 60 oC for a 16 hour time frame. Work up and isolation was the same as for 4.4.3.2.  143  5 Conclusions Several new cyclopentadienyliron compounds of linear, star-shaped, first generation dendrimer and hyperbranched morphologies were prepared. These compounds and their precursors were tested spectroscopically using 1H and 13C NMR and IR. Thermal analysis was conducted via TGA and DSC for all of the prepared polymers. Analysis using POM was carried out on selected linear monomers and polymers. As applicable, testing for molecular weights was also accomplished via GPC or viscometry depending on the polymer morphology. Solubility was found to be variable via manipulation of functional groups. In general, it was found that the introduction of cyclopentadienyliron complexes increased the solubility over organic analogues. Higher molecular weights were found to decrease solubilities whereas more branch points, even if accompanied by increased molecular weights caused an increased solubility. The primary goal of investigating the influence of structure (morphological and bond type) on the thermal properties was achieved. In general it was found that the cyclopentadienyliron moiety decreased the thermal stability. The presence of ester bonds in conjunction with ether bonds had the effect of decreasing the thermal stability of the backbone of the prepared compound in comparison to similar purely ether bonded compounds. An increased number of branch points were found to decrease the temperature of the phase transitions with little influence on the thermal stability. Allowing gelation to occur during the formation of the hyperbranched polymers resulted in decreased losses during thermal degradation. Alteration of hard/rigid areas with soft/flexible regions allowed  144  for the introduction of thermochromic properties and increased ordering of the materials as illustrated by crystallization and melting in the DSC thermograms. Several star-shaped molecules, select linear polymers and all soluble hyperbranched polymers were analyzed by solution viscosity in DMSO. The relative, specific, reduced, and inherent viscosities were calculated. Intrinsic viscosities were found using the Huggins, Kramer and Fuoss plots/equation. For those compounds of known molecular weights, Mark-Houwink plots were constructed and the constants determined. Based upon the Huggins and Kramer constants, molecular compactness and the shrinking factors, the starshaped molecules assumed a spherical shape in DMSO. This caused the Mark-Houwink equation to become invalid as seen in the obvious poor estimation of molecular weights for the hyperbranched polymers. Preparation of a calibration curve and scaling factor using the inherent viscosity calculated at 0.5 g/dL from the Kramer equation, molecular weights of the hyperbranched and linear polymers could be estimated relative to star-shaped molecules and previously reported linear polymers of known/approximated molecular weights.  145  6 Future work Directions for the future are not limited solely to the continuation of the presented polymer morphologies, bond types and means of analysis from within this thesis. As outlined within the introduction, several areas of cyclopentadienyliron containing compounds and polymers had not yet been explored. This thesis lays the ground work for future studies with star-shaped, dendrimeric and hyperbranched morphologies as well as the incorporation of ester bonds into these compounds. The area of crosslinked polymers was begun by my lab mates, Nelson Pereira and Diana Winram.245 The preparation of water soluble cyclopentadienyliron complexes and the introduction of amide bonds has yet to be fully developed. The following section will delineate the work that has been done to illustrate the plausibility of water soluble cyclopentadienyliron complexes along with their properties.  6.1 Water soluble complexes 6.1.1 Introduction Amino acids are commonly thought of as biochemical molecules where natural polymers containing amino acids are referred to as peptides, proteins or enzymes depending on the length and function of the polymer.306 The aforementioned polymers consist of natural amino acids linked via peptide or amide linkages.306 The most popular method of preparing these synthetically was developed by Merrifield et al.307 His method involved the use of a solid support to attach the growing peptide chain and the use of dicyclohexylcarbodiimide (DCC) as a coupling agent in the presence of an amine.307 Synthetic amino acid containing polymers may be made to mimic naturally occurring compounds, that is, with the peptide linkage308-314 or they may be prepared using only one  146  of the amino acids functional groups to give non-amide linked polymers and macromolecules.76,77,315-320 Encapsulation and association of amino acids into prepared synthetic polymers and dendrimers has also been reported.321-325 This may occur via chelation of the amino acid with a metal. In a few cases, the chelation of a metal with an amino acid resulted in a coordination polymer.326-328 More commonly, small complexes result depending on the functional groups available in the amino acid and the metal used in chelation.329-359 Introduction of metals to amino acids may also be accomplished via pi-bonding or covalent linkages to metal containing compounds such as ferrocene.312,313,360-363 The thermal properties of iron containing amino acids have not been examined. Thermal analysis of copper chloride glycine and copper chloride lysine complexes showed that the first weight loss, occurring between approximately 180-400 oC, corresponded to the loss of the amino acid ligands.344 Mass losses above 400 oC to approximately 700 oC were found to be sublimation of the resultant copper chloride.344 Infrared spectroscopy of metal chelated amino acid ferrocenes have shown that the asymmetric carbonyl stretch is in the range of 1550-1570 cm-1 and the symmetric carbonyl stretch appears between 1415-1445 cm-1, as either one or two bands depending on the chelated metal.361 Similar free amino acid ferrocenes structures showed the carbonyl stretch in the range of 1700-1790 cm-1.361 Depending on the method of binding between an amino acid and the metal ion, that is, where chelation with the carboxylate increased the amount of hydrogen bonding of the amine via other amino groups with strong IR peaks, whereas ionic interactions with the carboxylate decreased the amount hydrogen bonding leading to weak/non-existent IR peaks.331  147  Purely organic amino acids show variable infrared spectra depending on the molecular charge of the amino acid.364 In the zwitterionic form, the amine shows a stretch between 3100-2600 cm-1, an asymmetric overtone stretch between 2222-2000 cm-1 which disappears upon substitution of the amine and a torsional oscillation overtone around 500 cm-1. There is a symmetrical bend between 1550-1485 cm-1 and an asymmetric bend between 1660-1610 cm-1. The carboxylate shows an asymmetric stretch between 16001590 cm-1 and a weak symmetric stretch around 1400 cm-1. Sodium salts show little change with the amine asymmetric stretch overtone diminishing and the amine stretch found between 3400-3200 cm-1.364 Barium salts show minor shifts from the zwitterionic form.359 The hydrochloride salts show shifts in the amine bands with the asymmetric bend between 1610-1590 cm-1 and symmetric bend between 1550-1480 cm-1.364 The carboxylate stretch appears between 1220-1190 cm-1. Free thiols appear as weak stretches between 2600-2550 cm-1 with a carbon-sulphur stretch visible between 700-600 cm-1. Disulphide linkages, when present appear very weakly between 500-400 cm-1.364 In general, the bonding of heavier elements causes a shift to lower vibrational frequencies and increased positive charge on a metal center causes an increase in wave number due to a lower amount of electron donation by the metal.365 Various (η6-arene)(η5-cyclopentadienyl)iron complexes bound via an amine linkage to protected amino acids have been prepared.363 The use of L-cysteine or L-methionine at elevated temperatures for a short period of time resulted in the formation of the amine linkage in 50-70 % yields. Analysis of the 13C NMR data for the methionine complex in a D2O/DMSO (10:1) solvent mixture showed that the cyclopentadienyl carbons appeared at 76.80 ppm and the quaternary complexed aromatic at 126.69 ppm. The complexed 2,6-  148  arene carbons appeared at 68.97 and 69.33 ppm due to the two diastereomers induced by the chirality of the amino side chain. The remaining complexed aromatic carbons were visible at 81.76 and 86.85 ppm. The carbonyl carbon resonated at 181.10 ppm and the carbon next to both the amino and the carbonyl at 58.76 ppm. The aliphatic CH2 of the methionine chain appeared to 32.77 and 31.22 ppm with the isolated CH3 attached to the sulphur at 15.58 ppm. 1H NMR and 1  13  C NMR spectra for the cysteine complex as well as  H NMR spectrum for the methionine complex were not reported.363 Thermal analysis,  other forms of spectral analysis, metal coordination or biological studies were not undertaken on any of these complexes or complexes with other amino acids.363 In this chapter, cyclopentadienyliron complexes were reacted with the amino acid cysteiene to give water soluble complexes. These complexes were then coordinated to the transition metals cobalt, iron and nickel or to the main group metal tin. The were analyzed using NMR, IR, Vis, TGA and DSC. This work was undertaken to see if stable water soluble cyclopentadienyliron complexes could be prepared and if so do they have any potential biological applications or metal chelation abilities.  6.1.2 Results and discussion 6.1.2.1 Synthesis and properties of cyclopentadienyliron amino acids The unnatural amino acids were prepared using a mixed solvent system of water to solubilize the amino acid and DMF to solubilize the iron complex. Formation of the unnatural amino acid was aided by the addition of potassium carbonate and isolated by removal of the water and precipitation from methanol into DMF as seen in scheme 6.1. The amino group of cystiene displays a pKa of 10.28 for formation of the neutral amine, while the side chain thiol has a pKa of 8.18, 306 thus it is expected that a thiol linkage will occur.  149  However, the formation of a disulphide linkage via a two electron oxidation306 may occur as iron has previously been reported to cause oxidation.69,70,306 These complexes displayed behaviour similar to that of an amino acid as opposed to the cyclopentadienyliron complex, that is, they displayed limited water and alcohol solubility instead of enhanced solubility in organic solvents such as acetone, dichloromethane and DMSO. K2CO3, DMF, distilled water  O Cl  R  HS Fe+PF6-  OH NH2  2.1, R = Cl 1.37b, R = CH3 1.37a, R = H 1.33, R =  R  S Fe+PF6-  6.1 O  HS  O OH  R  NH O  NH2  Fe+PF6- HO and/or 6.2a-d  OH  O  O  Scheme 6.1 Reporting of the NMR shifts will follow the convention of Roberts and Johnsen363 where the doublets are attributed to the nitrogen lone pair being in either the endo or exo position of the conformational isomers. These isomers were shown to be the result of restricted rotation around the arene-nitrogen bond resulting in the formation of a chiral nitrogen as opposed to a long range effect of the amino acids chiral carbon. Carbon 1 (C1) refers to the aromatic carbon bound to the amino acid with the remains of the aromatic carbons numbered as per usual around the ring whereas C1’ is the carbonyl carbon, C2’ the chiral carbon and C3’ the carbon with the thiol. Reporting of the proton shifts follows the same numbering scheme. As is readily apparent for these samples, there is a mixture of both possible products. Bonding via the amino group appears to have predominated based upon 1H NMR  150  spectra shifts, although small amounts of the thioether derivative are present. The two products were differentiated based upon comparision of the complexed aromatics and cyclopentadienyliron shifts to those of previously reported compounds363 as well as the thioethers presented earlier. For the major, amine linked product, the cyclopentadienyl protons were sometimes hidden within the water peak of the deuterated water or deuterated methanol when used. In compound 6.2b, the CH appeared at 3.98 ppm as a broad singlet and the CH2 as a set of doublets due to chirality at 2.76 ppm (J = 10 Hz) and 3.15 ppm (J = 10 Hz). The heteroatom bonded proton (thiol) was found at 5.76 ppm. The cyclopentadienyl protons were found near the water peak at 4.65 ppm. The complexed aromatics of the amine linked product appeared at 5.27 and 5.43 ppm for the protons next to the amine and at 5.69 and 5.78 ppm for those next to the methyl. The methyl protons resonated at 2.12 ppm. The thioether linked product was formed in smaller amounts. The peaks appearing at 6.41 and 6.82 correspond to the complexed aromatics, with the related cyclopentadienyliron protons appearing at 5.59 ppm. A resonance peak at 6.47 ppm may be related to the amine at 6.47 ppm. The minor peaks at 1.1, 1.8 and 8.5 ppm correspond to the solution degradation product. Sharp singlets centered around 3 ppm and a singlet around 8 ppm corresponded to the reaction solvent DMF. Acetone is responsible for the peak at 2.04 ppm. Figure 6.1 shows the proton NMR of compound 6.2b.  151  Figure 6.1 1H NMR spectrum of 6.2b in D2O (at 500 MHz) Table 6.1 1H NMR values and yields for 6.2 (in D2O omitting 6.2d in MeOH)(at 200 MHz omitting 6.2a at 300 MHz and 6.2b at 500 MHz) Yield H2,6 H3,5 Cp R Hetero H2’ H3’ 5.32 (d, J 5.83 (d, J = ---, 6.01 (s), 4.12 2.90 (d, J = 6.2a 80 = 5.5 Hz), 6.9 Hz), 5.04 6.45 (s) (s) 6.6 Hz), 3.27 5.53 (d, J 5.91 (d, J = (d, J = 6.3 = 5.5 Hz), 6.6 Hz), Hz) 6.57 (s), 7.24 (d, J = 6.65 (s) 6.0 Hz) 5.27 (s), 5.69 (s), 4.65, 2.12 5.76, 3.98 2.76 (d, J = 6.2 95 5.43 (s), 5.78 (s), 5.59 (s) 6.47 (brs) 10 Hz), 3.15 b 6.41(s) 6.82 (s) (d, J = 10 Hz) 5.50 (s), 5.65-5.85 4.77, over- 6.56, 4.00 3.01 (brs), 6.2c 88 5.58 (s) (m) 5.34 lap 7.08 (brs) 3.43 (brs) (m) 5.45-5.71 6.00 (brs) --1.68, 6.58, 4.08 3.00 (brs), 6.2 89 (m) 1.99, 6.94 (brs) 3.52 (brs) d 2.45, 7.11, 7.38 (brs) Secondary confirmation of assignment of the protons of the major product in the spectra was accomplished using COSY NMR. In this sample of 6.2b seen in figure 6.2, the  152  CH2 was split as a doublet at 2.80 and 3.11 ppm with interactions between the two protons as well as to the CH of the cysteine (3.98 ppm). The methyl attached to the complexed aromatic appeared at 2.12 ppm, whereas the complexed aromatics were visible in the range of 5.26-5.82 ppm. The cyclopentadienyl protons were clearly visible at 4.65 ppm as opposed to the usual region between 5-6 ppm. This may be due to the interaction of the lone pair of nitrogen interacting with the iron. Cyclopentadienyliron protons in ferrocene derivatives128,129,134,227 appear around 4 ppm due to the presence of two singlely anionic pidonor groups. Anomalous peaks may be seen at 3.43 ppm coupling to the solution degradation product at 1.03 ppm. These peaks correspond to the degradation of the synthesized compounds.  Figure 6.2 COSY NMR of 6.2b in D2O (at 500 MHz) The  13  C NMR was run as an attached proton test for 6.2c, the Cp carbons of the  major, amine linked product were readily visible at 76.19 ppm. The complexed CH were  153  found at 75.26, 85.41 and 86.51 ppm as expected and the quaternary carbon found at 122.75 ppm. The carbons from the amino acid were found at 26.61 ppm for the CH2, 57.24 ppm for the CH and 172.89 ppm for the carbonyl carbon. This spectra may be seen in figure 6.3 where the strong resonance at 39.5 ppm is due to residual solvent in the deuterated solvent.  Figure 6.3 13C APT NMR of 6.2c in DMSO (at 200 MHz) Table 6.2 13C NMR values the HMBC) C1 C2,6 71.15 6.2b^ 122.75 75.26 6.2c* 1  for 6.2 (* DMSO at 200, APT) (^ D2O at 500, HSQC,  +  C3,5 90.96 85.41  C3’ 44.00 26.62  C4 R 102.01+ 22.40 86.51 ---  Cp 78.42 76.19  C1’ 172.89  C2’ 61.66 57.24  from  H-13C-gradient selected-HSQC for 6.2b illustrated that the cyclopentadienyl  protons of the amine linked product were clearly within the water peak at 4.65 ppm in the proton NMR and that the complexed aromatics were shifted to the 5.2-6.0 ppm range as may be seen in figure 6.4. These correlated with the carbon shifts of 78.42 ppm for the cyclopentadienyl carbons and 90.96 and 71.15 ppm for the complexed aromatics. The lack of a carbon correlation for the proton peak at approximately 5.7 ppm gave further indication that this peak was the amine. The CH was confirmed to appear at 61.66 ppm in the carbon and 3.98 in the proton, whereas the CH2 appeared as a doublet of doublets with an identical carbon shift at 44.00 ppm and two protons at 2.80 and 3.11 ppm. The methyl 154  attached to the complexed aromatic appeared clearly at a proton shift of 2.12 ppm with the methyl carbon at 22.40 ppm. The peak at proton shift of 1.80 ppm and carbon shift of 26.00 ppm is that which appears after the sample is in solution for more than approximately 1 hour and is due to degradation of the product leading to precipitation.  Figure 6.4 HSQC 6.2b in D2O (at 500 MHz) Detection of heteronuclear multiple bond correlations was attempted for the reasonably soluble 6.2b in D2O. Upon analysis of the 1H-13C-HMBC spectra displayed in figure 6.4, it became obvious that relaxation times were drastically different between that of the aliphatic cysteine portion of the molecule and the aromatic complexed portion of the molecule. As a result, the collection of spectral data was terminated prematurely and only partial analysis is possible. The cyclopentadienyl cross peak showed up underneath the water peak with multiple couplings due to the ringed structure with a carbon shift of 77.80 and protons between 4.45 ppm and 4.70 ppm. The methyl attached to the complexed aromatics was further confirmed to be appearing at 2.12 ppm and showed primary  155  connectivity to the quaternary carbon at 102.01 ppm and secondary connectivity to the complexed CH at 90.06 ppm confirming the HSQC assignment. Interestingly, the degradation product containing a proton appearing at 1.8 ppm correlated to a carbon at 188 ppm.  Figure 6.5 HMBC of 6.2b in D2O (at 500 MHz) As can be seen in the vis data (table 6.3, figure 6.6 of 6.2b), the unnatural amino acids displayed water solubility as well as sparing solubility in some organic solvents. The predominate band displayed was around 405 nm and corresponded to the absorbance of blue-violet with the reflection of yellow. The shoulders between 460-480 nm corresponded to the absorbance of blue-green with the reflectance of orange and red.  156  Figure 6.6 Vis spectrum of 6.2b Table 6.3 Vis data for 6.2 in nm (where NS means not sufficiently soluble/turbid solution and --- means no band present) water 10% HCl EtOH DMSO DMF THF 352 406 --NS NS NS 6.2a 408 406/466 410/480 NS 414 NS 6.2b 406 406/476 412/464 NS NS NS 6.2c 404 NS 406 NS NS NS 6.2d  As can be clearly seen from the IR data, all samples displayed hydrogen bonding via the carboxylic acid of the amino acid as seen in figure 6.7 and table 6.4. Bands were assigned via comparison of the starting materials and similar reported compounds.361 The amine group appeared as expected. A slight shift in the chelated carbonyl stretches may be noted between cyclopentadienyliron complexes and ferrocene complexes361 with the asymmetric stretch between 1500-1400cm-1 and the symmetric stretch between 14001350cm-1. There were no absorptions present in the region of the free amino acid carbonyl stretches and the absorbancies from the cyclopentadienyliron complexes between 16701570cm-1 were unchanged in strength relative to the starting complexes (1.33, 1.37a,b, 2.1) without bound amino acids.  157  Figure 6.7 IR spectra of 6.2 prepared as KBr pellet Table 6.4 IR data for 6.2 in cm-1 H-bond From cysteine 3330 (b) 3075 (b), 2927 (b), 2507 (b), 6.2a 1908 (w, bridging C=O), 1390 (s), 1249 (s), 690 (s), 639 (w), 558 (w) 3408 (b) 2942 (b), 2626 (b), 1400 (s), 6.2b 1372 (s), 702 (w), 659 (w), 549 (w) 3288 (b) 2973 (b), 2618 (b), 14456.2c 1366 (s), 701 (w), 659 (w), 554 (w) 3387 (b) 3078 (b), 2962 (b), 1491 (s), 6.2d 1390 (s), 1235 (s), 690 (w), 617 (w)  From complex 1908 (w, bridging C=O), 1664 (s), 1620 (s), 1558 (s), 1079 (w), 1006 (m), 836 (s) 1647 (s), 1627 (s), 1007 (m), 832 (s)  1646 (s), 1635 (s), 1007 (m), 846 (s), 832 (s) 1621 (s), 1570 (s), 1008 (m), 833 (m)  From this, it is possible that the carbonyl group is capable of chelating the iron (II) of the cyclopentadienyliron complex leading to degradation. Chelated iron in the presence of thiols with cleavage of a carbon-carbon bond alpha to an amino and a carboxylic acid has been previously reported.69 X-ray crystallography may be used to confirm this hypothesis of chelation as well as show if the carbonyl is inter or intra molecularaly bound.  158  Attempts at crystal growth have resulted in higly disordered crystals unsuitable for single crystal diffraction. The samples showed a thermal transition at approximately 125 oC as may be seen in table 6.5. Decomposition of the samples started at a low temperature. The first thermal loss, occurring between 155-205 oC may have been due to solvent evaporation from solvent coordinated to the amino acid. The loss starting at 210 oC and finishing around 280 oC corresponded to the degradation of the cyclopentadienyliron moiety. Breakage of the amine linkage between the cysteine and the complex occurred between 350-445 oC. Thermal weight losses above 600 oC correspond to the breakdown of aromatics and aliphatics remaining. Unnatural amino acid 6.2a may be seen in figure 6.8. Table 6.5 Thermal analysis of 6.2 (DSC from run b) T1 T2 Weight Tonset Tendset Loss (oC) (oC) (%) 129 7 175 183 6.2a 30 254 378 123 17 177 203 6.2b 10 211 266 10 346 418 127 17 157 203 6.2c 6 265 273 5 354 370 6 413 444 93 126 8 155 182 6.2d 13 227 282 10 399 444  Weight Loss (%) 26  Tonset (oC)  Tendset (oC)  835  958  8 9  498 858  626 938  9 11  739 878  811 939  18 6  623 862  694 913  159  Figure 6.8 TGA thermogram of 6.2b Antibacterial tests were conducted using a number of different bacteria (table 6.6) in which the size of the zone of inhibition of bacterial growth around an inoculated sterile disk was measured. All results showed that the unnatural amino acids were non-toxic under the conditions used. Possible reasons for this include the relative non-toxicity of iron metal as well as the possibility that the unnatural amino acid was unable to cross the cellular membrane. Table 6.6 Biological testing of 6.2, where positive controls were CIP=ciprofloxacin, P=Penicillin G, E=Erythromycin and C=Chloramphenicol, negative control was N=EtOH solvent used for dissolving compounds and compounds were run at maximum concentration in EtOH. All measurements are in mm. CIP P E C N 6.2a 6.2b 6.2c S. aureus 26 21 24 22 0 0 0 0 S. agalactiae 18 31 30 22 0 0 0 0 E. faecalis 20 10 0 30 0 0 0 0 E. coli 37 0 0 23 0 0 0 0 P. aeruginosa 20 0 0 10 0 0 0 0 C. xerosis 0 16 42 40 0 0 0 0 B. cereus 23 0 25 26 0 0 0 0  160  6.1.2.2 Synthesis and properties of metal chelates of cyclopentadienyliron amino acids Coordination of a second metal to the unnatural amino acid occurred via heating of the appropriate metal chloride with the amino acid in solution with a base such as potassium carbonate. The structure drawn for compounds 6.4-6.6 in scheme 6.2 may vary in regards to the bonding between the carboxylate, amine, iron and metal, that is, based upon the previous discussion of complexes 6.2 and published amino acid chelates,358 other methods of bonding are possible. The trimetallic compounds were isolated via pouring the reaction solution into ether and filtration. The products were isolated in reasonable yields as powders. Only selected trimetallic compounds were prepared and analyzed in order to examine general properties. 6.2a-d 6.4 = MCl2 DMF, 60 oC 3 hr  M, a = Sn b = Co c = Fe d = Ni  O OH O  S R  M  NH O Fe+PF6- HO  S  H N  PF6-  +  Fe  R  R  S Fe+PF6-  and/or  O NH2  Fe+PF6-  M  NH2 S  O  R  O  6.4b,c, R = Cl 6.5a,d, R = CH3 6.6a, R = H  Scheme 6.2 The cobalt derivative was found to be moisture sensitive. That is the coordination around the cobalt could be determined by the colour of the complex. When it was first isolated, the colour was green; blue from the four coordinate cobalt plus the yellow of the unnatural amino acid. Upon sitting open to the air or with the addition of water, the  161  complex changed to a dirty pink colour; pink from the six coordinate cobalt plus the yellow of the unnatural amino acid. As with the uncoordinated unnatural amino acids, the cyclopentadienyl protons commonly overlapped with the water peak. When the coordinated metal was cobalt, NMR was not possible due to the paramagnetic nature of cobalt and the diamagnetic requirement of NMR. As may be seen in figure 6.9 of 6.5a and table 6.7, the CH proton was found to shift from 3.98 ppm to higher ppm of 4.17 upon coordination of the amino acid with a metal centre, while the CH2 protons were also shifted. The complexed aromatics of the amine linked product were found in the range of 5.4-6.0 ppm, closer to the normal range for complexed aromatics, although still significantly shifted to lower ppm. The thioether linked product gave complexed aromatic resonances at 6.74 ppm (J = 3.0 Hz) and 7.15 ppm (J = 3.3 Hz). Sharp singlets around 3 ppm and 8 ppm correspond to residual reaction solvent DMF. Most of the trimetallic complexes were insufficiently soluble to allow for data collection within a reasonable amount of time and their solubilities were found to decrease with time. This decreased solubility was found to be accompanied with an appearance of a singlet proton at approximately 1.25 ppm.  162  Figure 6.9 1H NMR spectrum of 6.5a in D2O (at 300 MHz) Table 6.7 1H NMR values and yields of 6.4-6.6 in D2O (at 300 MHz). Yield H2,6 H3,5 R Cp Hetero paramagnetic 6.4b 69 ppt in solution 6.4c 62 5.48 (d, J = 5.99 (t), 2.38 4.94, 6.63, 6.5a 93 6.9 Hz), 5.73 7.15 (d, J = (s) 5.13 6.70 (d, J = 6.3 3.3 Hz) Hz), 6.74 (d, J = 3.0 Hz) 5.44 (brs), 5.80 (brs), 2.20 --6.18, 6.5d 71 5.62 (brs), 5.93 (brs), (s) 6.32 6.59 (brs) 6.95 (brs) 5.80 (brs), 6.09 (d, J = over4.93, 5.58 6.6a 94 5.95 (brs), 5.4 Hz), lap 5.00, 6.62 (s), 6.69 6.82 (s), 5.21 (s) 7.32 (s)  H2’  H3’  4.17 (brs)  2.81 (d, J = 5.1 Hz), 3.76 (d, J = 8.7 Hz)  4.11 (brs)  3.25 (brs)  4.23 (brs)  2.87 (brs), 3.22 (brs), 3.82 (brs)  Proton assignment for compound 6.5a was confirmed via COSY NMR as seen in figure 6.10. The complexed aromatics were seen to correlate to each other between 5.31 with 5.76 ppm and 5.90 with 6.06 ppm. The cyclopentadienyl protons appears as the large, non coupled peak at 4.80 ppm. The methyl group attached to the complexed aromatic was clearly visible at 2.20 ppm. The protons of the cysteine were found at 2.94 and 3.78 ppm.  163  The heteroatom accounted for the uncoupled proton at 6.17 ppm showing a shift from the unnatural amino acid not complexed to tin.  Figure 6.10 COSY NMR of compound 6.5a in D2O (at 200 MHz) As may be seen in figure 6.11, with values in table 6.8, the 13C DEPT135 NMR of compound 6.5a shows the methyl group attached to the complexed aromatic at 25.53 ppm. The CH2 and CH of the cysteine portion of the molecule were found at 49.46 and 72.95 ppm respectively. The complexed CH appeared at 74.19 and 92.10 ppm with the cyclopentadienyl carbons resonating at 82.26 ppm. Quaternary carbons do not appear in a DEPT135 spectra. The cysteine CH showed a shift of approximately 10 ppm upon complexation of the cysteine to the tin.  164  Figure 6.11 13C DEPT135 NMR for 6.5a in D2O (at 400 MHz) Table 6.8 13C NMR values for 6.5a C2,6 C3,5 DEPT 74.19 92.10 HSQC 72.20 90.96  R 25.53 22.51  Cp 82.26 79.96  C2’ 72.95 62.25  C3’ 49.46 44.05  Correlation NMR allowed for confirmation of proton and carbon assignments for the major amine linked product of 6.5a and may be seen in figure 6.12. The methyl attached to the complexed aromatic appeared as the cross peak at 2.29 and 22.51 ppm and the cyclopentadienyl appeared at 4.69 and 79.96 ppm. The complexed aromatic cross peaks appeared as a doublet of doublets centered at 5.40 and 72.20 ppm along with 5.75 and 90.96 ppm. The CH from the cysteine appeared at 4.00 and 62.25 ppm with the CH2 doublet at 2.80 and 3.22 ppm in the proton correlating to 44.05 ppm in the carbon. The heteroatom proton, by lack of carbon correlation, was assigned to have shifted upon chelation of the tin to 6.5 ppm.  165  Figure 6.12 HSQC for 6.5a in D2O (at 500 MHz) As seen in table 6.9, the samples showed a larger range of solvents in which they were soluble, the individual solubilities in a solvent decreased, however, upon metal complexation. The absorption bands shifted minimally for tin, iron and nickel whereas the values for cobalt were significantly different from those of the uncomplexed unnatural amino acid. Most notable was the colour change of the solid, non-soluble powder in THF to the original four coordinate cobalt from the hydrated six coordinate cobalt. The intensity of the absorbance at approximately 400 nm was found to be dependant upon the compound tested as may be noted via comparisons between chelated unnatural amino acids 6.5d and  6.4b in figures 6.13 and 6.14. All values are given in table 6.9.  166  Figure 6.13 Vis spectra of 6.5d Table 6.9 Vis data for 6.4-6.6 in nm (where NS means not soluble/turbid solution) water 10% HCl EtOH DMSO DMF THF 366/582 404/580 388/582 NS NS green NS 6.4b NS NS 386/486/582 NS NS NS 6.4c 398 400 410/472 408/424 414 NS 6.5a 402/484/576 400/472 410 410 412 NS 6.5d 404 398 412 416 406/424 NS 6.6a  Figure 6.14 Vis spectra of 6.4b Upon coordination, the appearance of a new band in the IR fingerprint region was visible for all samples prepared (6.4b, 6.5d, 6.6a in figure 6.15, table 6.10). In some cases, a bridging carbonyl carbon band was also discernible and a decrease in the band around  167  1105 cm-1 was noted in other cases. A minor shift towards higher wave number for the aromatic carbon stretches of the cyclopentadienyliron complex was noted, corresponding to stronger bonding between the iron and the aromatic rings. A change in the coordination of the carbonyl from the iron in complex 6.2 to the introduced metal would account for this shift. Hydrogen bonding was clearly visible in several cases. The weak amine asymmetric stretch overtone was diminished in strength in relation to the uncomplexed amino acid compounds. This may be explained by coordination of the amine to the introduced metal in the minor thiol linked product.  Figure 6.15 IR spectra of 6.4b, 6.5d, 6.6a Table 6.10 IR data for 6.4-6.6 in cm-1 New 970 (m) 6.4b 990 (m), 980 (m) 6.4c 977 (m) 6.5a 965 (m) 6.5d 979 (m) 6.6a  Bridging Carbonyl 1852 (w)  Changes 1109 (w) 1109/1104 (w)  1862 (w)  168  Thermal transitions were noted to occur at approximately 85 oC and 115 oC (figure 6.16 of 6.3a, 6.4b,c, table 6.11). The large endothermic peak around 85 oC may be due to the loss of coordinated water. TGA showed that the unnatural amino acids had increased stability upon complexation of the metal, with each only losing ~30% of their mass below 650oC (table 6.11, figure 6.17 of 6.5a). These weight losses corresponded to loss of the cyclopentadienyliron moiety and breakdown of the amine linkage. It may be noted that after heating the samples to 1000 oC, the samples did not display the characteristic charred appearance, but rather were light green, white or pink in appearance.  Figure 6.16 DSC thermogram for 6.2a, 6.4b,c Table 6.11 Thermal analysis for 6.4-6.6 (DSC from run c) T1 T2 Weight Tonset Tendset o Loss ( C) (oC) (%) 89 115 4 95 112 6.4b 14 161 182 5 383 376 88 120 7 161 176 6.4c 10 260 322 84 182 18 165 184 6.5a 5 356 363 78 111 15 120 170 6.5d 5 247 267 102 114 16 167 196 6.6a 4 453 528  Weight Loss (%) 30  Tonset (oC)  Tendset (oC)  800  942  11 27 5 27 7 26 23  627 820 584 789 353 751 863  676 927 619 933 383 923 993  169  Figure 6.17 TGA thermogram for 6.5a The biological toxicology of the chelated unnatural amino acids was tested with results shown in table 6.12. The chelated complexes were found to not inhibit the growth of several bacterial strains under normal conditions with release from inoculated sterile disks. Table 6.12 Biological testing for 6.4-6.6 as applicable, where positive controls were CIP=ciprofloxacin, P=Penicillin G, E=Erythromycin and C=Chloramphenicol, negative control was N=EtOH solvent used for dissolving compounds and compounds were run at maximum concentration in EtOH. All measurements are in mm. CIP P E C N 6.4b 6.4c 6.5a 6.5d 6.6d S. aureus 26 21 24 22 0 0 0 0 0 0 S. agalactiae 18 31 30 22 0 0 0 0 0 0 E. faecalis 20 10 0 30 0 0 0 0 0 0 E. coli 37 0 0 23 0 0 0 0 0 0 P. aeruginosa 20 0 0 10 0 0 0 0 0 0 C. xerosis 0 16 42 40 0 0 0 0 0 0 B. cereus 23 0 25 26 0 0 0 0 0 0  170  6.1.3 Experimental 6.1.3.1 Characterization 1  H and  13  C NMR were collected using one of the following instruments: Gemini  200 NMR spectrometer (200 and 50 MHz, respectively); Bruker Avance DXP300 spectrometer (300 and 75 MHz, respectively); Bruker Avance 400inv spectrometer (400 and 100 MHz, respectively); Bruker AMX500 spectrometer(500 and 125 MHz, respectively). Solvent residues or potassium carbonate were used as reference.366 Chemical shifts were calculated in ppm and J couplings reported in hertz (Hz). Differential Scanning Calorimetry (DSC) was done using a Mettler 821e with a heating rate of 20 oC/min under a flow of nitrogen. Thermogravimetric analysis (TGA) was run on a Mettler TGA/SDTA851e with a heating rate of 20 oC/min under a flow of nitrogen. Infrared spectroscopy (IR) was accomplished using KBr pellets on a Bomen, Hartmann & Braun FTIR. Ultraviolet-visible spectroscopy (UV-vis) was done using quartz cuvettes on an HP 8452A Diode-Array UVVisible spectrophotometer.  6.1.3.2 Materials Complexes 2.1, 1.37a, b and 1.33 were prepared according to previously established  methodologies.121,125,133,137,151,227  Cysteine  (6.1)  and  ammonium  hexafluorophosphate were purchased from Aldrich. Tin (II) chloride dihydrate (6.4a), iron (II) chloride tetrahydrate (6.4c) and cobalt (II) chloride hexahydrate (6.4b) came from Fisher. Nickel (II) chloride hexahydrate (6.4d) was supplied by Baker. All solvents were HPLC grade and used without purification. Antibacterial tests were conducted according to literature procedures and strains.367  171  6.1.3.3 Procedures 6.1.3.3.1 Synthesis of 6.2a-c In a 50 mL flask, the cyclopentadienyliron complex was added (0.5 mmol) as was L-cysteine (2.0 mmol), potassium carbonate (10 mmol) and a stir bar. With stirring, distilled water was added slowly until the cysteine and potassium carbonate were completely in solution. DMF was then added slowly with continued stirring until the iron complex had dissolved. The reaction was then purged under nitrogen and continued in the dark with continued stirring. After 16 hours, the reaction mixture was placed on a rotary evaporator to remove the water. The residue was then dissolved using a MeOH/DMF mixture (approximately 4 MeOH to 1 DMF). The product in solution was then filtered and the MeOH evaporated. The resultant solid was then filtered, washed with DCM and allowed to dry under reduced pressure in the dark.  6.1.3.3.2 Synthesis of 6.2d Using the same procedure as for the other unnatural amino acids with the following amounts of starting materials: valeric acid complex (0.3 mmol), L-cysteine (1.2 mmol) and potassium carbonate (5 mmol).  6.1.3.3.3 Synthesis of 6.4-6.6 The unnatural amino acid (0.5 mmol), the appropriate metal chloride (0.25 mmol) and potassium carbonate (2.5 mmol) were placed in a 50 mL round bottom flask with a stir bar. With stirring and a condenser, 5 mL of DMF was added and the reaction mixture was heated for 3 hours at 60 oC in the dark. The reaction mixture was then allowed to cool slightly and poured into ether. The product was then filtered and allowed to dry under reduced pressure in the dark.  172  6.1.4 Conclusions Several new unnatural amino acids containing iron were prepared. These were found to degrade over time. 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