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Coordination chemistry of tetraneopentoxyphthalocyaninatocobalt(II) Wu, Haiying 1991

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COORDINATION CHEMISTRY OF TETRANEOPENTOXYPHTHALOCYANINATOCOBALTOI) By HAIYING WU B.Sc, Xiamen University, 1984 A THESIS IN PARTIAL FULPILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES Department of Cherristry We accept this as confcixming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA May 1991 ©HaiyingWu, 1991 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. DE-6 (2/88) ii ABSTRACT The thesis work reports developments in the coordination chemistry of tetra-neopentoxyphmalocyaninatocobalt(II) (CoTNPc) complexes. The preparation, characteri-zation, and ligand binding measurements in solution of seven new compounds are described in this thesis. Some additional complexes are studied in situ. Measurement of the equilibrium constants by UV-visible spectroscopy for the 1:1 binding reactions of the axial ligands (L = imidazole, N-memyUmidazole, pyridine, 4-picoline, 4-re^butylpyridine, piperidine, tetrahydrofuran) to CoTNPc in toluene solution allow for an estimation of the enthalpies for the binding of the N-donor ligands (7-12 kcal/mol) and the O-donor ligand (~ 4 kcal/mol). The order of equilibrium constants for ligand binding at room temperature is found to be: N-Melm > pip > 4-fBupy > Im > py > THF. Seven five-ccordinate CoTNPc species have been isolated (L = N-Melm, py, 4-pic, 4-*Bupy, pip, THF, DMSO) and characterized by elemental analyses, and UV-visible, MS (FAB), and NMR spectroscopy. The magnetic moment of CoTNPc in the solid state is found to be 2.23 ± 0.10 B.M. at ambient temperature, while the magnetic moment is 2.47 ± 0.10 B.M. in toluene solution. The magnetic moment of the five-coordinate species (py)CoTNPc is 2.61 ± 0.10 B.M. in toluene solution. It is concluded that CoTNPc and the five-coordinate complex (py)CoTNPc at room temperature are low spin with one unpaired electron. The ! H NMR spectra of the paramagnetic species (CoTNPc, LCoTNPc, L = Im, N-Melm, py, 4-pic, 4-'Bupy, pip, THF, PPI13) are studied. The ! H NMR spectra of CoTNPc are found to be solvent dependent; the a- and |3-proton signals of the phthalocyanine ring are very broad in DMSO-d6 and benzene-dg, and in chloroform-di these signals are so broad that they could not be observed. Some irregular multiplicities in these proton NMR spectra result from the cobalt(II) complexes being mixtures of isomers. The isotropic shift vs.l/T Curie plot for (py)CoTNPc shows that the extrapolated isotropic shifts of the benzo-, methylene, and methyl protons on the phthalocyanine ring at infinite temperature are not zero, indicating there is a contribution from a dipolar interaction. For the axial ligands, the proton signals of the methyl groups of some ligands (L = N-Melm, 4-pic, 4-rBupy) are observed, and these signals are averaged by rapid chemical exchange between the free and coordinated ligands; the ligand aromatic proton signals of these ligands are not observed. However, the 2 H NMR spectra, when L = pyridine-dg, show that the y- 2 H signal shifts in a direction different to signals from the a - and |5-2H deuterons, suggesting a contact shift mechanism is dominant in this case. The 3 1 P NMR spectra of in situ PPh3/CoTNPc samples do not give any peaks, indicating that signals for the phosphine are extremely broad. The elemental analyses, UV-visible spectra, IR, NMR, and ESR results suggest that CoTNPc and its five-coordinate species do not bind oxygen at the temperatures exarriined (77 K to ambient temperature). iv Table of Contents ABSTRACT ii Table of Contents iv List of Tables vi List of Figures vii List of Abbreviation and Symbols x ACKNOWLEDGEMENTS xi Chapter! Introduction 1 1.1 Five- and Six- Coordinate Cobalt(II) Phthalocyanines 2 1.2 The Oxygen Binding of Cobalt(H) Phmalocyanine Complexes 4 1.3 Reactivity of Cobalt Phthalocyanine and its Derivatives 5 References 6 Chapter H Experimental Procedures 8 II. 1 Materials 8 n . l .a Gases 8 n.l.b Solvents 8 II.1.C Reagents 8 n.2 Instrumentation 9 n.3 Tetraneor^ ntoxyphmalocyamnatocobalt(II) .9 11.4 Preparation of Five-Coordinate Tetraneopentoxyphthalocyaninatocobalt(n) Complexes 10 11.5 Ligand Binding Measurements 14 References 16 Chapter m. Thennodynamic Studies on Ligand Binding to Tetraneopentoxyphthalocyaninatocobalt(II) 17 III.l Introduction 17 UI.2 Observation and Treatment of Data 18 HI.3 Results and Discussion 21 References 33 Chapter IV. Magnetic Behavior of Tetraneopentoxyphthalocyaninatocobalt(II) 34 IV.l Introduction 34 IV. 2 Results and Discussion 35 References 41 Chapter V. Spectroscopic Data fOTTetraneopentoxyphmdocyaninatocobalt(II) and its Five-Coordinate Adducts 42 V. l Introduction 42 V.2 Proton NMR Data 43 V.2.a Solvent Effects 57 V.2.b Multiplicities 59 V.2.c Isotropic Shifts 63 V.3. Deuterium NMR 64 V.4 Phosphorus-31 NMR and Proton NMR Spectra of in situ (PPh3)CoTNPc 68 V.5 ESR Spectra 71 V.6 Irifrared Spectra 71 References 75 Chapter VI General Conclusions and Some Recommendations for Future Work 78 Appendices I. UV-Vis extinction coefficients for CoTNPc in toluene at ambient temperature 81 II. Raw data and data analysis for ligand binding to CoTNPc 82 III. Raw data and data analysis for susceptibility measurement of CoTNPc .. 95 vi List of Tables table cage. III.l Thermodynamic data for binding of axial ligands to CoTNPc in toluene solutions 29 in. 2 Ligand binding constants for some cobalt porphyrins and phthalocyanines 32 V.l *H NMR data for five-coordinate LCoTNPc complexes 44 V.2 *H NMR data for CoTNPc in different solvents 57 V.3 Deuterium NMR data for pyridine-ds in a toluene solution of CoTNPc 67 V.4 Proton NMR data for the axial ligand of (PPh3)CoTNPc 68 vii List of Figures figure page LI Tetraneorjentoxyphthalocyaimi^  2 II. 1. Room temperature lH NMR spectrum of PfeTNPc in chloroform-di 11 II. 2 Anaerobic UV-vis cell designed for ligand binding experiments 15 IH. 1 Visible spectral changes observed for binding of 4-picoline to CoTNPc in toluene at 21.0 °C 19 III. 2.a Hill plots for Im + CoTNPc in toluene 22 111.2. b van't Hoff plot for the binding of imidazole to CoTNPc 22 111.3. a Hill plots for N-Melm + CoTNPc in toluene 23 III.2.b van't Hoff plot for the binding of N-Melm to CoTNPc 23 IIIAa Hill plots for py + CoTNPc in toluene 24 111.4. b van't Hoff plot for the binding of pyridine to CoTNPc 24 111.5. a Hill plots for 4-pic + CoNTPc in toluene 25 111.5. b van't Hoff plot for the binding of 4-picoline to CoTNPc 25 111.6. a Hill plots for 4-'Bupy + CoNTPc in toluene 26 III.6.b van't Hoff plot for the binding of 4-'Bupy to CoTNPc 26 IIL7.a Hill plots for pip + CoNTPc in toluene 27 m.7.b van't Hoff plot for the binding of piperidine to CoTNPc 27 III.8.a Hill plots for THF + CoTNPc in toluene 28 III. 8.b van't Hoff plot for the bmding of tetrahydrofuran to CoTNPc 28 IV. 1 Variation of magnetic susceptibility w i t h temperature for CoTNPc 36 IV.2 Variation of 1/Xm with temperature for CoTNPc 37 IV.3 Variation of the magnetic moment with temperature for CoTNPc 38 TV .4 Assumed d-orbital energy splitting and energy states for square-planar, low spin Co(II) 39 viii IV. 5. Linear plot of 1/Xm vs. T in the low temperature range 40 V. 1 Room temperature *H NMR spectra of CoTNPc in different solvents: (a) Chloroform-di, 0>) benzene-d6, (c) DMSO-d6. 46 V.2 Room temperature *H NMR spectrum of (py)CoTNPc in toluene-dg 47 V.3 Room temperature lH NMR spectrum of (N-methylimidazole)CoTNP in benzene-d6- 48 V.4 Room temperature *H NMR spectrum of (4-picoline)CoTNPc in benzene-d6. 49 V.5 Room temperature *H NMR spectrum of (4-fm-butylpyridine)CoTNPc in benzene-d6 50 V.6 Room temperature J H NMR spectrum of (piperidine)CoTNPc in chloroform-di 51 V.7 Room temperature lH NMR spectrum of (THF)CoTNPc in benzene-ds 52 V.8 Room temperature *H NMR spectrum of (PPh3)CoTNPc with excess PPh3 in benzene-dg 53 V.9 Room temperature ! H NMR spectrum of CoTNPc and 4-'Bupy in C6D6 with [4-'BupyV[CoTNPc]t (a) 1:1, (b) 4.6:1, (c) 8.2:1 56 V. lO.a 1 H NMR spectra for the benzo-protons of (py)CoTNPc at various temperatures in toluene-dg 60 V. lO.b ! H NMR spectra for the methylene protons of (py)CoTNPc at various temperaturesin toluene-dg 61 V.lO.c *H NMR spectra for the methyl protons of (py)CoTNPc at various temperatures in toluene-dg 62 V. 11 Curie plot of (py)CoTNPc in toluene-ds 65 V. 12 Room temperature 2 H NMR spectra of pyridine-ds in benzene-d6, (a) with and fjb) without CoTNPc 66 V. 13 Room temperature ! H NMR spectra of PPh3 in CoTNPc solution. ix (a) free PPI13, (b) P P h 3 ( ~ 37 mM) containing CoTNPc (~ 3.1 mM), (c) PPh3 (~ 63 mM) containing CoTNPc (~ 3.1 mM) 70 V. 14 Configurations of coordinated dioxygen in metalloporphyrin and metallophtjhalccyariine dioxygen adducts 72 V. 15 The infrared spectra of CoTNPc and (py)CoTNPc (KBr pellets) 74 X List of Abbreviations and Symbols 4-Uupy 4-rerr-butylpyridine CoPc phthalocyanmatocobalt(II) CoTNPc tetraneopentoxyphmalocyammtocobaltfjl) CoTSPc tetrasulfonatophthalocyaniiiatoro^  DMSO dimethylsulfoxide DTA differential thermal analysis ESR electron spin resonance Im imidazole NMR nuclear magnetic resonance N-Melm N-meftylimidazole OEP 2,3J,84243J7,18-octaemylrx)rphyrin dianion OMBP octiimeihyltetrabenzoporphyrin dianion Pc phthalocyanine dianion 4-pic 4-picoline pip piperidine Ph3P triphenylphosphine PpDME protoporphyrin DC dimethyl ester dianion py pyridine salen N,N-bis(saUcylaldehyde)emylene<tiimine THF tetrahydrofuran TGA theniiogravimetric analysis TPP mew-tetraphenylporphyrin dianion VSM Vibrating Sample Magnetometry X magnetic susceptibility x i ACKNOWLEDGEMENTS I wish to express my deepest gratitude to Professor B. R. James, whose guidance and encouragement have been an invaluable support throughout my research. I am indebted to all the members of Professor James1 research group, in particular to Drs. D. Thackray and N. Rajapakse for reading the thesis and useful discussions in general. I would also like to thank Professor R. C. Thompson and his students Mr. J. Du and Mr. T. Otieno for the measurement of magnetic susceptibilities and helpful discussions, and Professor H. G. Herring for recording of the ESR spectra. Financial support of this research from the Pulp and Paper Research Institute of Canada and the Natural Science and Engineering Research Council of Canada is gratefully appreciated. 1 Chapter I Introduction In the pulp and paper industry, the conventional pulp bleaching using chlorine-based reagents produces toxic and carcinogenic chlorinated organic compounds.1 The introduction of oxygen-containing reagents (e.g., O2, H2O2) leads to a considerable reduction in the amounts of pollutants formed. But the oxygen-based pulping process has not won widespread recognition as an alternative to existing pulping methods. One of the reasons for this is that alkaline conditions normally used for oxygen bleaching can result in a reduction of the strength properties of the product, e.g., the cellulose is degraded as well as the lignin.2 Coupled with this is that the low solubility of oxygen in aqueous solution which requires the use of high pressures to ensure that sufficient oxygen is available for pulping to proceed at a reasonable rate. For these reasons, attention is directed toward developing a catalyst which would selectively increase the rate of dehgnification and which is effective under mild conditions, thereby minimizing the amount of cellulose degradation.2 In 1983, a white rot fungus, phanerochaete chrysosporium, was discovered to be able to degrade lignin.3 Like hemoglobin and myoglobin, the active site of the ligninase contains an iron porphyrin compound. This biological system suggests a possible model to study the dehgnification. Phthalocyanine is a porphyrin-like compound, cobalt complexes of which are capable of reversibly binding oxygen and have previously been shown to catalyze the auto-oxidation of phenols in organic solvents.4 Since phenol oxidation is a critical reaction in the oxygen delignification process,5 the catalytic oxidation chemistry of cobalt phthalo-cyanine seems of potential interest in this aera. However, the coordination chemistry of metaUophthalocyanines has been relatively poorly developed because the complexes are generally insoluble in almost all solvents.6 Recently, a class of cobalt complexes (Fig. 1.1) has been synthesized by Leznoff and his coworkers, and the species are very soluble in organic solvents.7 R=-CH2-C(CH3)3 Figure 1.1. Tetraneopentoxyphmalocyaninatocobalt(IJ), 1 (CoTNPc) This thesis work is focused on the coordination chemistry of this neopentoxy derivative. The measurement of equilibrium constants for ligand binding, some aspects of the magneto-chemistry, and some 1 H, 2 H and 3 1 P NMR spectra will be discussed in chapters 3,4, and 5 respectively. The coordination chemistry of cobalt phthalocyanine complexes is briefly summarized in this chapter. 1.1. Five- and Six-Coordinate Cobalt(II) Phthalocyanines Cobalt(II) phthalocyanines are insoluble in almost all solvents; however, if the cobalt(II) complex is heated in pyridine or other N-donor solvents, solid products with some axial ligands can be obtained. The square-planar cobaltfjl) phthalocyanine complex (CoPc) readily binds one or two donor molecules in the axial positions:8 L + CoPc , LCoPc (1.1) 2L + CoPc • L2CoPc (1.2) Under appropriate conditions five- or six-coordinate complexes can be formed; e.g., five-coordinate complexes precipitate from hot solutions of a base such as pyridine (py) while six-coordinate complexes crystallize from the same solutions at room temperature (L = py, 3-picoline).8 These adducts have a very low solubility and only dissolve in boiling ligand solvents; no solution NMR data have been reported. Six-coordinate complexes contain two equivalent Co-L bonds and no evidence is seen for the stepwise loss of L and the intermediate formation of a five-coordinate complex by thermal analysis (TGA, DTA), which shows reformation of the four-coordinate precursor.8 The extent of the axial interaction is in the order expected from the donor strengths of the ligands to a metal center: Im > py > DMSO.9 The synthesis of the low-spin complex [CoPc(3-pic)] by a procedure similar to that noted above has been reported.10 If, however, this solid is slurried in neat base at ambient temperature for 15 days, the complex becomes high spin.10 This is very unusual because other cobalt(II) porphyrins and phthalocyanines, whether square-planar, five- or six-coordinate complexes, do not give high spin forms.4 The cobalt(II) complexes of some tetrakis (f-butyl)-, methoxy-, and nitro-substituted phthalocyanines and their pyridine adducts have been prepared.lla« l l b Although only penuicoordinate complexes are isolated, it is found that the cobalt derivatives exist as hexacoordinate complexes in solution at a high ligand concentration.110 Other bidentate, bridging ligand (e.g., pyrazines, 4, 4-bipyridine, and 1,4-diazabicyclo [2.2.2] octane) adducts have also been obtained.lld All these complexes are proved to be in low spin forms by ESR and magnetic susceptibility measurements, but no NMR spectra are reported. It have been demonstrated that there are intermolecular interactions in solid CoPc;12 analysis of the ESR spectra of two forms (a and P polymorphs) indicates that inter-molecular axial interactions between cobalt and an aza nitrogen of another molecule are greater in the a form than that in the P form. 1.2. The Oxygen Binding of Cobalt(II) Phthalocyanine Complexes Cobalt(H) phthalocyanine does not bind oxygen in donor solvents at room temperature although the presence of one trans axial ligand is believed to facilitate oxygen binding. Indeed, if the temperature is sufficiendy low (e.g., at liquid N2 temperature), reversible binding of oxygen is observed.13 LCoPc + 0 2 ^ = = f c r LCoPc(02) (1.3) The ESR spectra are consistent with the formation of a superoxide species LCo(UI)Pc(02")13 The stability of the oxygen adducts is influenced by the nature of the trans axial ligand because ESR signal intensities and hyperfine coupling constants indicate that the oxygen adduct with picoline is more stable than that with hexamethyl-phosphoramide.13 Oxygen binding is also noted with L2C0PC (L = py, 4-picoline) in CH2CI2 at -115 *C to give LCoPc(02), the dissociation of one donor c>ccurring prior to oxygenation.8 Recently reported is a single ESR spectrum thought to contain the signals for (py'bPcCo11 [Pc. = tetrakis (3,5-di-r-butyl-4-hydroxyphenyl) dodecachlorophthalocyanine dianion], the cation radical ConEc+- and pyComPjc(02").14 The species CoTSPc4" (TSPc = tetrasulfonatophthalocyanine anion) with an axial • ligand reacts with dioxygen, the products depending on the donor properties of the axial ligand. In the case of L = CN" or OH", the products are free 02" and (L)Co(III)TSPc4\ The presence of imidazole (Im) enhances the formation of an 02-adduct as (Im)CoTSPc-02. In the presence of ascorbic acid as an axial ligand, a complete electron transfer from this ligand to dioxygen, i.e., the oxidation of the ligand, occurs.15 A supposed five-coordinate cobalt(II) complex may fail to show an ESR signal because of dimerization to a metal-metal bonded species, and the following reaction can give a binuclear O2 adduct of the n-peroxo type which is also ESR silent.14 LPcCom(02-) + LPcCo11 LPcCom(02)2-ComPcL (1.4) 1.3. Reactivity of Cobalt Phthalocyanine and Its Derivatives Cobalt(II) phthalocyanines can be reduced by BH4- in DMF, 1 6 and CoTSPc4" can be reduced in neutral water by hydrazine or sodium sulphite, to generate Co(I) species.17 The Co (I) species is a powerful nucleophile, the oxidative reaction with CH3I resulting in a Co(ni) complex.17 The lH NMR spectrum of (CH3)Co(HI)TSPc4- in deuterium oxide shows the benzo resonances at 8.9 ppm and the axial methyl resonance at - 6.1 ppm The reduction of ConTNPc to [CoJtTNPc]- occurs at - 0.91 V in 0-C6H4CI2 and -0.85 V in DMF (vs. ferrocemum-ferrocene).18a>18b Oxidation of CoIITNPc occurs at the cobalt ion or at the macrocycle ring, depending on the solvent used; the presence of solvents which can co-ordinate axially to the cobalt ion favour the product [Co^TNPc]-1", otherwise, the product is [Co n TNPc 1 -] + . 1 8 a « 1 8 b Some dicobalt covalendy-linked diphthalocyanines Have been described.18 The electrocatalytic activity of mono-cobalt and di-cobalt tetraneopentoxyphthalocyanines for the reduction of molecular oxygen has been investigated. 1 8 c » 1 8 d These cobalt complexes immobilized onto ordinary pyrolytic graphite catalyze the electroreduction of oxygen by two electrons to give peroxide.1811 Mixed-valence behavior is observed within Co^Co111 and CcflCcJ dinuclear tetraneopentoxyphmalocyanines.18e-18f References 1. R. P. Singh, The Bleaching of Pulp, Tappi Press, Atlanta, 1979. 2. M. B. Hocking, Modern Chemical Technology and Emission Control, Springer-Verlag, New York, 1985, p300. 3. (a) M. Tien and T. K. Kirk, Science, 221, 661 (1983). (b) F. P. Guengerich, Crit. Rew. Biochem. Mol. Biol., 25, 97 (1990). 4. L. J. Boucher, In Coordination Chemistry of Macrocyclic Compounds, G. A. Melson ed., Plenum Press, New York, 1979, p461. 5. T. J. Fullerton and S. P. Ahern, TAPPI, 61(12), 37(1978). 6. K. Kasuga and M. Tsutsui, Coord. Chem. Rev., 32, 67 (1980). 7. C. C. Leznoff, S. M. Marcuccio, S. Greenburg, A. B. P. Lever, and K. B. Tomer, Can. J. Chem., 63, 623 (1985). 8. F. Cariati, D. Galizzioli, F. Morazzoni, and C. Busetto, / . Chem. Soc. Dalton Trans., 556(1975). 9. L. D. Rollman and S. I. Chan, Inorg. Chem., 10, 1978 (1971). 10. F. Cariati, F. Morazzoni, and C. Busetto, / . Chem. Soc. Dalton Trans., 496 (1976). 11. (a) J. Metz and M. Hanack, Nouv. J. Chim., 5, 541 (1981). (b) J. Metz, O. Schneider, and M. Hanack, Inorg. Chem., 23, 1065 (1984). (c) M. Hanack and J. Metz, Chem. Ber., 120, 1307 (1987). (d) M. Hanack, S. Deger, and A. Lange, Coord. Chem. Rev., 83, 115 (1988). 12. J. N. Assour and W. K. Kahn, / . Am. Chem. Soc, 87, 207 (1965). 13. C. Busetto, F. Cariati, D. Galizzioli, and F. Morazzoni, Gaz. Chim. Ital., 104, 161 (1974). 14. E. R. Milaeva, A. Szeverenyi, and L. I. Simandi, Inorg. Chim. Acta , 167,139 (1990). 15. D. M. Wagnerova, K. Lang, and W. Damerau, Inorg. Chim. Acta, 162,1 (1989). 16. P. Day, H. A. O. Hill and M. G. Price, / . Chem. Soc. (A), 90 (1968). 17. D. H. Busch, J. H. Weber, D. H. Williams, and N. J. Rose, J. Am. Chem. Soc, 86, 5161 (1964). 18. (a) W. Liu, M. R. Hempstead, W. A. Nevin, M. Melnik, A. B. P. Lever, and C. C. Leznoff, / . Chem. Soc. Dalton Trans., 2511 (1987). (b) W. A. Nevin, M. R. Hemptead, W. Liu, C. C. Leznoff, and A. B. P. Lever, Inorg. Chem., 26, 570 (1987). (c) M. R. Hempstead, A. B. P. Lever, and C. C. Leznoff, Can. J. Chem., 65, 2677 (1987). (d) P. Janda, N. Kobayzshi, P. R. Auburn, H. Lam, C. C. Leznoff, and A. B. P. Lever, CanJ. Chem., 67, 1109 (1989). (e) C. C. Leznoff, H. Lam, W. A. Nevin, N. Kobayzshi, P. Janda, and A. B. P. Lever, Angew. Chem. Int. Ed. Engl, 26, 1021 (1987). (f) N. Kobayzshi, H. Lam, W. A. Nevin, P. Janda, C. C. Leznoff, and A. B. P. Lever, Inorg. Chem., 29, 3415 (1990). Chapter II Experimental Procedures ILL Materials II. La. Gases Argon (Linde, Union Carbide) was passed through a CaS04 (Hammond) column to remove moisture, then through a Ridox column (Fisher Scientific) to remove oxygen. Nitrogen (Linde, Union Carbide) and oxygen (Linde, Union Carbide) were used without further purification. H.l.b. Solvents Solvents such as toluene (BDH) and tetrahydrofuran (BDH) were distilled under nitrogen from sodium-benzophenone ketyl. 2-(N, N-dimethylamino)ethanol (Sigma) and N, N-dimethylformamide (BDH) were used without further purification. The anhydrous toluene was stored in vacuo over sodium benzophenone ketyl in a glass container with a Kontes high vacuum Teflon valve after several freeze-pump-thaw cycles at 10-3 torn Deuterated solvents, such as benzene-d6 (CIL), chloroform-di (CIL), dimethyl-sulphoxide-d6 (SDL), and toluene-ds (MSD), were stored over molecular sieves (4 A, MCB) or used as purchased. Degassed solvents were obtained after several freeze-pump-thaw cycles. II. I.e. Reagents Cobalt(H) in the form of C0CI26H2O was purchased from BDH and used without further purification. Piperidine (ICN Pharmaceuticals), pyridine (BDH), 4-picoline (BDH), 4-te/t-butyl-pyridine (Aldrich), and N-methylimidazole (Aldrich) were distilled from KOH or used without further purification. Imidazole was recrystallized from toluene and dried under vacuum for 24 hours. Thin-layer chromatography was carried out using silica gel 60 F254 (Merck) as the adsorbent 11.2. Instrumentation Electronic absorption spectra were recorded on a Cary 17 or a Perkin Elmer 525 instrument equipped with thermostated cell holder. The infrared spectra were recorded on a Perkin Elmer 1600 Nicolet 5 DX instrument, samples being prepared as KBr pellets. Nuclear magnetic resonance spectra were measured on a Varian XL-300 (300 MHz for protons) spectrometer. The solvent peaks (arising from r^ oton-containing components) were used as internal standards: benzene-d<5 (7.15 ppm), toluene-d8 (methyl protons at 2.09 ppm), chloroform-d (7.25 ppm), DMSO-dg (2.49 ppm). ESR spectra were kindly collected by Dr. F. G. Herring employing a home built ESR spectrometer. Fast atomic bombardment (FAB) mass spectra were obtained on an MS-9 mass spectrometer using p-nitrobenzyl alcohol as the matrix. Magnetic susceptibility was measured using a vibrating sample magnetometer (Model 155, EG&G Princeton Applied Research) over the temperature range 4 to 80 K, and a Gouy balance (V-2300-A, Varian Associates) over the range from room temperature to 77 K, by Mr. J. Du and Mr. T. Otieno of Dr. R. C. Thompson's group. Microanalyses were performed by Mr. P. Borda of this Department. 11.3. Tetraneopentoxyphthalocyaninatocobalt(II), 1 Metal-free tetraneopentoxyphthalocyanine, as a mixture of isomers, was kindly provided by Prof. Clifford C. Leznoff of York University. The phthalocyanine ligand (H2TNPC) is a deep blue solid. Anal, calcd. for C52H58N8O4: C, 72.70; H, 6.81; N, 13.04. found: C, 72.56; H, 6.97; N, 12.60. *H NMR (CDCI3, 300 MHz): 7.20 - 8.70 (m, 12H, aromatic), 3.90 - 4.26 (m, 8H, CH20), 1.40 (m, 36H, CH3), -3.53 (t, 2H, H2TNPc) (Figure II. 1). UV-vis spectrum (in CH2CI2, nm): 704, 688,642, 608 (sh),388 (sh), 340, 288. The UV-vis data agree with those given in the literature,1 but the NMR data have not previously been reported. Tetraueopentoxyphmalocyanmatxx:obalt(Tl) was prepared according to the literature procedure.1 Cobalt(II) chloride (18 mg, 0.074 mmol) was added to tetraneopentoxy-phthalocyanine (33 mg, 0.038 mmol) dissolved in 3 ml of 2-(N,N-dimethylamino)ethanol and DMF (2:1 in volume) and the mixture was heated to 110 "C under argon for one hour. After being cooled to room temperature, the mixture was passed through a silica gel column using distilled toluene as the eluting solvent2 to give 20.5 mg of CoTNPc in 58.3% yield, as a dark blue solid. Anal, calcd. for C52H56N8O4C0: C, 68.18; H, 6.16; N, 12.23. Found: C, 68.22; H, 6.14; N, 12.07. UV-vis spectrum (in toluene, nm, log e): 673.5 (5.08), 607 (4.52), 333 (4.78). (in CH 2 C1 2 , nm, log e): 674 (4.76), 610 (4.44), 383 (4.41), 329 (4.63), 288 (4.71). Appendix I gives the raw data for the detennination of extinction coefficients. IR spectral data (cm-1): 1616, 1239, 1098, 1064, 745. Mass spectrum (m/e): 915±1 (M+, 100%), 900, 884, 858, 845. The IR and mass spectral data agree with those given in the literature.1 The UV-vis data in CH2CI2 given in ref. 1 approximate to those listed above, although the Amax values in the literature are in each case 7 nm higher than those deterrnined in the present work. II.4. Preparation of Five-Coordinate Cobalt(II) Tetraneopentoxyphthalo-cyanine Complexes Typically, complex 1 (10 mg, 0.010 mmol) was dissolved under air in toluene (2 ml) in a vial, and 5 pi (0.10 mmol) of a neat ligand (liquid at room temperature) was added to the blue solution. The solution immediately became more intense blue. After the solvent and excess ligand were removed in vacuo and the product was dried under vacuo for 24 s i | i i i i | i i r T ) H i i | i M i | i i i i | i i i i | j i . | i i i i | i i H | i i i t | i n - 3 ,1 1 -J 4 - 3 -.1 A -4 0 "I'M I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 1 ^ I I I I I I I f I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I ' I 9 8 7 6 5 4 3 2 1 PPM Figure ELL Room temperature i H NMR spectrum of H2TNPC in chloroform-di. S = non-deuterated solvent signal. X = impurities. hours (< 10-3 torr), 8.5 mg of the product was obtained (in each case, ~ 80% yield). The samples was stored in a desiccator, except where noted. The ligands used here were N-methylimidazole, imidazole, pyridine, 4-rerr-butylpyridine, 4-picoline, piperidine, tetrahydrofuran (THF) and DMSO. (pv^ CoTNPc When the synthesis was performed as described, and after the product was dried under vacuo and the sample was stored under argon, the elemental analysis was as follows: calcd. for C57H61N9O4C0: C, 68.80; H, 6.18; N, 12.67. Found: C, 68.54; H, 6.34; N, 12.35. MS (m/e): 916±1 (CoTNPc+). UV-visible spectrum (in toluene, nm, in presence of excess py under argon or air): 329 (4.79), 607 (4.47), 666 (4.94). When (py)CoTNPc was exposed to the air for several hours, the microanalysis data found: C, 66.81; H, 6.28; N, 12.04. For the incorporation of one dioxygen or two water molecules, the expected analyses are: for (py)CoTNPc(02), Calcd. for C 5 7 H 6 1 N 9 O 6 C 0 : C, 66.66; H, 5.99; N, 12.27; for (py)CoTNPc-2H20, Calcd. for C 5 7 H 6 3 N 9 O 6 C 0 : C, 66.39; H, 6.15; N, 12.22. The results suggest that the pyridine complex is air- or moisture-sensitive. However, the UV-visible spectrum of pyCoTNPc in toluene is independent of the presence or absence of O2 or air, and it is concluded that (py)CoTNPc is probably hygroscopic. (N-Melm^CoTNPc The elemental analyses: calcd. for C55H60N10O4C0: C, 67.39; H, 6.26; N, 14.03. Found: C, 67.31; H, 6.39; N, 13.80. MS (m/e): 916±1 (CoTNPc+). UV-visible spectrum (in toluene, nm, in presence of excess N-methylimidazole under argon or air): 330 (4.81), 607 (4.47), 667 (4.94). (4-pic)CgTNPc The elemental analyses: calcd. for C58H63N9O4C0: C, 69.03; H, 6.29; N, 12.49. Found: C, 68.89; H, 6.38; N, 12.22. MS (m/e): 915±1 (CoTNPc+) UV-visible spectrum (in toluene, nm, in presence of excess 4-picoline under argon or air): 330 (4.79), 607 (4.47), 666 (4.95). I4ifBupy)CoTNPc The elemental analyses: calcd. for C61H69N9O4C0: C, 69.63; H, 6.61; N, 11.98. Found: C, 69.62; H, 6.82; N, 11.78. MS (m/e): 916±1 (CoTNPc+), 136 (4-*Bupy+). UV-visible spectrum (in toluene, nm, in presence of excess 4-terf-butylpyridine under argon or air): 326 (4.94), 607 (4.47), 665 (5.03). (pip^ CoTNPc The elemental analyses for: calcd. for C57H67N9O4C0: C, 68.38; H, 6.75; N, 12.59. Found: C, 68.77; H, 6.83; N, 12.35. MS (m/e): 915±1 (CoTNPc+). UV-visible spectrum (in toluene, nm, in presence of excess piperidine under argon or air): 332 (4.81), 607 (4.47), 667 (4.92). (THF)CoTNPc The elemental analyses; cald. for C56H64N8O5C0: C, 68.07; H, 6.53; N, 11.34. Found: C, 68.40; H, 6.38; N, 11.39. MS (m/e): 915±1 (CoTNPc+) UV-visible spectrum (in toluene, nm, in presence of excess THF under argon or air): 330 (4.82), 607 (4.42), 668 (5.00). fDMSO^CoTNPc-HoO The elemental analyses showed that (DMSO)CoTNPc is probably hygroscopic: calcd. for C56H70N8O7S2C0 [(DMSO)CoTNPcH20]: C, 64.08; H, 6.37; N, 11.07. Found: C, 64.13; H, 6.12; N, 11.26. Presumably as H 2 T N P C is a mixture of four isomers which are inseparable (see Chapter V), CoTNPc is also isolated as an isomer mixture3 and no crystals of 1 or the five-coordinate complexes suitable for crystal analysis could be obtained. II.5. Ligand Binding Measurements The equilibrium constant measurements for ligand binding reactions (over the temperature range 9-45 °C): nL +CoTNPc • LnCoTNPc (II. 1) 1 were performed using UV-visible spectroscopy. The variation of absorbance at 673.5 nm (a Xmax of i) with changes in ligand concentration was monitored. Aliquots of degassed neat ligand or ligand dissolved in toluene (typical concentration was 1.2 x 10'2 M) were added using a calibrated syringe to the cobalt complex solution, all under argon. The cell was sealed with a Kontes high vacuum Teflon valve (Figure n.2). The addition of a ligand or ligand solution changes the concentration of the cobalt complexes, so a dilution correction on the absorbances was made (Aconected in Appendix H). Typically, to achieve a fully formed five-coordinate complex (the data establish that n = 1) in order to obtain a "Aw" value, 5 p.1 neat ligand were added. For the case (e.g., TFfF) which had a small equilibrium constant, 0.5 ml of the neat ligand were added. The initial concentrations of CoTNPc were detenriined by using its known extinction coefficient, while the ligand concentrations were tetermined by volume or weight measurements. Graphical analysis of the titration data was carried out with Cricket Graph software (Cricket Software) on a Macintosh II personal computer. Figure EL2. Anaerobic UV-vis cell designed for ligand binding experiment. B-14 Socket joint (to vacuum line) rubber stopper (inlet for sample injection) 5 mm Kontes high vacuum Teflon valve B-14 cone (capped when in use) - quartz cell window References C. C. Leznoff, S. M. Marcuccio, S. Greenberg, A. B. P. Lever, and K. B. Tomer, Can. J. Chem., 63, 623 (1985). T. W. Hall, S. Greenberg, C. R. McArthur, B. Khouw, and C. C. Leznoff, Nouv. J. Chim., 6, 653 (1982). W. Liu, M. R. Hempstead, W. A. Nevin, M. Melnik, A. B. P. Lever, and C. C. Leznoff, / . Chem. Soc. Dalton Trans., 2511 (1987). Chapter i n Thermodynamic Studies on Ligand Binding to Tetraneopentoxyphthalocyaninatocobalt(II) III.l. Introduction In biological systems, the myoglobin heme group has bound to one of its axial coordination sites an imidazole of a histidine residue; the sixth coordinate site, trans to the coordinated imidazole, is vacant in deoxymyoglobin and is the site for the dioxygen binding in oxymyoglobin.1 Studies on cobalt(II)-Schiff-base, -porphyrin, and -phthalocyanine complexes have demonstrated that reversible oxygen bmding is gready enhanced by the presence of a fifth ligand (see also Section 1.2.). It is also found that such Co(JJ) complexes are generally much more efficient for catalysis of phenol oxidation than four-coordinate ones, because the five-coordinate species have greater affinity for dioxygen.1*2 A number of Co(U) porphyrins have been tested for their affinity for binding to a Lewis base.1 The ligand binding of a cobalt(JJ) porphyrin, octamemyltetrabenzoporphyrin, which is structurally between a porphyrin and a phthalocyanine, has been measured by D. W. Smith formerly of this group.3 The bmding of a first axial ligand (L) to cobalt(U) octamemyltetrabenzorx>rphyrin (CoOMBP), measured by visible spectroscopy, occurs with greater affinity than observed for all other cobalt(II) porphyrin complexes. Also, LCoOMBP is shown by visible spectroscopy to bind a second axial ligand at higher concentrations in several cases. This tendency to bind a second ligand is attributed to the very weak c basicity of the OMBP dianion (relative to that of the Pc anion) which enhances axial ligand binding to the metal center.3-4 Knowledge of the stability of LCoTNPc in solution is required for studying the coordination chemistry of CoTNPc and catalytic activities of these compounds. The equilibrium constants, entropies, and enthalpies of ligand binding reactions measured in this study are presented in this chapter. III.2. Observation and Treatment of Data The ligand binding reaction studied in toluene is complete within the time of mixing. Clean isosbestic points (e.g. in Figure m i , at 694, 663, 615, 603, 380 nm) are observed, consistent with a simple equilibrium between the four- and (as the analysis shows) five-coordinate CoTNPc complexes. There is no evidence for formation of a six-coordinate complex because further addition of substantial amounts of ligand causes no change in the spectrum of the five-coordinate complex. The 1:1 ligand binding is demonstrated by the fact that the slopes of the log Y (a ratio of the concentrations of the two species) vs. log [L] plots (Figures ELI.2 - m.7.) are equal to 1.0 ± 0.2 (see below). Upon the addition of a ligand, the Soret band (at 333 nm) and the visible band (at 673.5 nm) are slighdy blue shifted. This behavior is in contrast with that of CoOMBP, in which both the Soret and visible band are both red shifted on addition of the first axial ligand.3 The equilibrium constant values were determined by titration of a toluene solution of CoTNPc with the neat ligand (L = THF) or ligand dissolved in toluene solution (L = Im, N-Melm, py, 4-pic, 4-fBupy, pip); the successive ligand additions result in successive absorbance decreases at 673.5 nm (e.g., Fig. DXl). The absorbance of the Soret band increased as aliquots of ligand were added, but the changes were much smaller than that of the visible band, and the latter were used for determination of equilibrium constants. The ligand binding reaction can be presented by the following: K nL + CoTNPc . L^CoTNPc (IH.l) 1 20 The equilibrium constant is calculated from: [LnCoTNPc] [CoTNPc] [L]n ( L L L Z ) The fraction, X, of LnCoTNPc present at a known ligand concentration was calculated from the following expression: where An is the absorbance when no ligand is present, A is the absorbance at a specific concentration of ligand, and Aoo is the absorbance when the Ln CoNTPc species is fully formed. (A and Aoo were corrected for any dilution due to ligand addition) From equation III.2, log = n log [L] + log K (III.4) and substituting for X gives, log = n log[L] + log K (III.5) If Yis defined as: y _ Ap - A A " Aoo (III.6) then from a plot of log Y vs. log [L], the slope of the line is n, the number of ligands bound to the complex, and the intercept on the abscissa gives the -log K value (a Hill plot). According to the following equation, . AH' AS! InK-- R T + R (IH.7) from a van't Hoff plot of In K vs. 1/T, the slope is -AH7R, and the intercept on the In K axis gives the AS7R value. The enthalpies and entropies of the ligand binding reactions are then readily estimated. in . 3. Results and discussion Hill plots and van't Hoff plots are shown in Figures in.2 - HJ.7. The raw data are listed in Appendix IL The slope of the Hill plots are 1.0 ± 0.2; the K values at various temperatures for the different ligands, and the corresponding AH" and AS" values, are given in Table D1.1. When anaerobic solutions of five-coordinate species were exposed to air, no changes in UV-vis spectra were observed, indicating that LCoTNPc did not bind oxygen at room temperature. For the THF system, under the conditions of the experiments, the concentration of adduct formed (up to ~ 10"5 M) was insignificant compared to the concentration of added ligand, and corrections for bound ligand were unnecessary when calculating the free ligand concentration in solution. However, for N-donor ligands, the equilibrium constant is larger at lower temperature, and at lower concentration of added ligand, a substantial amount of the added ligand coordinated to CoTNPc, which makes the actual concentrations of the free ligand in the solution lower than the total concentration of added ligand, and corrections were necessary in the calculations. For the THF/CoTNPc system, substantial amounts of ligand had to be added to "fully form" the adduct. This led to such a high ligand concentration in the solution (up to 15% by volume in toluene) that the nature of the solution with respect to solvation characteristics and dielectric constant was almost certainly affected. 22 logPm] Figure III.2.a. Hill plots for Im + CoTNPc in toluene. 11 9 g I • 1 • 1 • 1 • ' • 1 0.0031 0.0032 0.0033 0.0034 0.0035 0.0036 1/T(1/K) Figure III.2.b. van't Hoff plot for the binding of imidazole to CoTNPc. -6 -5 -4 -3 log [N-Melm] Figure UI.3.a. Hill plots for N-Melm + CoTNPc in toluene. 12 9 I • 1 i I i i i i • I 0.0031 0.0032 0.0033 0.0034 0.003S 0.0036 1/T(1/K) Figure IU.3.b. van't Hoff plot for the binding of N-Melm to CoTNPc. 24 log [py] Figure ffl.4.a. Hill plots for py + CoTNPc in toluene. 8 -—1 I 1 1— 1 -• - ... — 1 — • 1 1 . • -0.0031 0.0032 0.0033 0.0034 0.0035 0.0036 VT(1/K) Figure HI.4.b. van't Hoff plot for the bmding of pyridine to CoTNPc. log [4-pic] Figure in.5.a. Hill plots for 4-pic + CoTNPc in toluene. 10 9 —1 1 • 1 ' ' 1 1  -1 1 ••- « • 0.0031 0.0032 0.0033 0.0034 0.003S 0.0036 1/T(1/K) Figure III.5.b. van't Hoff plot for the bmding of 4-picoline to CoTNPc. 26 log [4-Bupy] Figure III.6.a. Hill plots for 4-' Bupy + CoTNPc in toluene. 11 i • i • i • i • 0.0031 0.0032 0.0033 0.0034 0.0035 1/T(1/K) Figure HI.6.b. van't Hoff plot for the bmding of 4-te^butylpyridine to CoTNPc. 27 B 10.0 °c © 21.4 °C A 45.0 °C -6 -5 -4 -3 log [pip] Figure m.7.a. Hill plots for pip + CoTNPc in toluene. g I i i i i i i i i i I 0.0031 0.0032 0.0033 0.0034 0.0035 0.0036 1/T(1/K) Figure H1.7.b. van't Hoff plot for the bmding of piperidine to CoTNPc. 28 -0.5 \-a 11.0 °c • 21.0 °C o 21.0 °C 41.0 °C 5 r i i i I -2.5 -1.5 -0.5 log [THF] Figure III.8.a. Hill plots of the binding of THF to CoTNPc. 0.0031 0.0032 0.0033 0.0034 0.0035 0.0036 1/T(1/K) Figure III.8.b. van't Hoff plot of the binding of THF to CoTNPc. Table ELT.1. Thermodynamic data for binding of axial ligands to CoTNPc in toluene solutions Ligand Temp.,a log Kb AH,C AS,d pKae •c M"1 kcal/rnole e.u. Im 9.0 4.45 -8.3 -9 6.95 21.0 4.22 31.0 4.02 45.0 3.73 N-Melm 9.0 5.04 -9.5 -11 7.25 21.0 4.74 31.0 4.57 45.0 4.19 py 9.0 3.91 -7.2 -8 5.27 21.0 3.70 31.0 3.51 45.0 3.29 4-pic 11.0 4.35 -10.2 -16 5.98 21.0 4.11 31.0 3.84 41.1 3.60 4-03upy 15.0 4.48 -11.7 -20 5.99 21.0 4.30 31.0 4.06 41.0 3.73 30 Table HI.1. Thermodynamic data for binding of axial ligands to CoTNPc in toluene solutions (continued) Ligand Temp.,a •c log K b M-l AH,c kcal/mole AS,d e.u. pKae pip 10.0 4.71 -11.1 -18 11.30 21.4 4.47 45.0 3.79 THF 11.0 1.34 -2.9 -4 -2.08 21.0 1.26 31.0 1.21 41.0 1.13 a. Temperature deviation ± 0.5 "C. b. Since error estimates are not very meaningful for such a small number of data points, the standard deviation derived from the least-squares analysis for log K is estimated to be 0.1.5 c. The standard deviation for AH is estimated to be 0.6 kcal/mol. d. The standard deviation for AS is estimated to be 2 e.u. e. The pKa of HL+ quoted by B. R. James, In The Porphyrins, D. Dolphin ed., Vol. V, Academic Press, New York, 1978, p264. Comparison of the equilibrium constants (e.g., at 21 °C) reveals that the extent of the axial interactions is in the following order N-Melm > pip > 4-fBupy > Im > 4-pic > py > THF. The N-donor ligands show larger binding ability than the single O-donor ligand as shown by their equilibrium constants at the same temperature. For N-donor ligands, the equilibrium constants are greater than 103 M _ 1 while that for THF is about one thousand times less. Also, the enthalpy for the binding of the O-donor ligand is smaller than those of the N-donor ligands, indicating that the Co-0 bond in these systems is weaker than a Co-N bond. A base having strong o-donor capacity with no 7t-acceptor strength, like piperidine, exhibits a binding enthalpy comparable to the other N-donor ligands listed, suggesting that the contribution from the o-donor ability of the axial ligand is more important than the Tt-acceptor property. Strengths of the Co-N (axial ligand) bonds in the 4-fBupy and 4-pic adducts are higher than the strength in the py adduct perhaps due to the higher o-donor abihty of 4-'Bupy and 4-pic, although their 7C-acceptor properties are weaker than those of py.6 The higher strength of the Co-N axial ligand bond in the N-Melm complex (vs. py) with CoTNPc is justified by its high o-donor ability.6 The basicity of phthalocyanines and porphyrins, and the basicity and number of axial ligands, determine the relative energies of the d z 2 and dx2-y2 levels of the cobalt center. The spin state and stereochemistry of the complexes are governed by these d-orbital energy levels. Weaker o-donor phthalocyanines or porphyrins would lower the d x 2 . y 2 orbital and the strong basic axial ligands raise the d z 2 orbital. Solely considering the electrostatic effect on the bmding ability of an axial ligand to a metallophthalocyanine or metalloporphyrin complex, the donor ligand electrons are more strongly attracted to a metal center with a higher positive charge. Thus, in a series of cobalt macrocycles, the weakest base (porphyrin or phthalocyanine dianion) should form the complex with the strongest bound axial ligand. Such considerations have been invoked to account for trends in axial ligand binding in five-coordinate cobalt porphyrin systems.3 Comparison of the equilibrium constants of the ligand binding for some Co-phthalocyanine and porphyrin systems (Table ITJ.2) indicates that the TNPc dianion is probably a stronger o-donor ligand than the OMBP dianion, a weaker o-donor ligand than the OEP dianion, and a o-donor ligand comparable to the PpDME dianion. The pK3 value of TNPc should be close to that ofPpDME(-4.8). Table IIL2. Ligand binding constants for some cobalt porphyrins and phthalocyanines8 COMPLEX LIGAND logK pK 3 d Co(OMBP) pip 4.9b -2.0 CoTNPc pip 4.3C Co(PpDME) pip 3.8b -4.8 Co(OEP) pip 3.3b -6 Co(OMBP) py 4.3b CoTNPc py 3.6C CofPpDME) py 3.8b Co(OEP) py 2.9b a. At 25 *C, data for CoTNPc taken from van't Hoff plots. b. From ref. 3. c. From this work. K 3 d. The K 3 defined as the equilibrium constant for [H3porp]+ • H+ + H2porp. References 1. B. R. James, In The Porphyrins, D. Dolphin ed., Academic Press, New York, vol. V, 1978, p201. 2. L. Salmon, C. Bied-Charreton, A. Gaudemer, P. Moisy, F. Bedioui, and J. Devynck, Inorg. Chem., 29, 2734 (1990). 3. D. W. Smith, Ph.D. thesis, University of British Columbia, 1980. 4. H. R. Harmer, K. J. Reimer, D. W. Smith, and B. R. James, Inorg. Chim. Acta, 166, 167 (1989). 5. D. V. Stynes, H. C. Stynes, B. R. James, and J. A. Ibers, / . Am. Chem. Soc, 95, 1796 (1973). 6. (a) F. Cariati, F. Morazzoni, and M. Zocchi, Inorg. Chim. Acta, 14, L31 (1975). (b) F. Cariati, F. Morazzoni, and M. Zocchi, J. Chem. Soc Dalton Trans., 1018 (1978). (c) F. Morazzoni, F. Cariati, and G. Micera, Spectrochim. Acta, 36(A), 867 (1980). Chapter IV Magnetic Behavior of Tetraneopentoxyphthalocyaninatocobalt(II) IV. 1. Introduction The planar, four-coordinate cobalt(JJ) complexes are usually low spin with magnetic moments between 2.2 B.M. and 2.7 B.M. at room temperature.1 Compared with the predicted spin-only value of 1.73 B.M., this rather large value of the magnetic moment is thought to result from incomplete quenching of the orbital moment, as occurs also in low spin cobalt(U) octahedral complexes.2 The P form of cobalt(U) phthalocyanine complex has a magnetic moment of 2.54 B.M. at room temperature which remains nearly constant down to about 20 K 2 The principle moments are highly anisotropic and it is shown that only the electronic configuration (d x z) 2(d y z) 2 (dxy)2(dz2)1 is compatible with this behavior.3 Another polymorphic form is a-cobalt(U) phthalocyanine. The magnetic moment of this compound at room temperature is 2.2 B.M., which remains constant down to 4 K. 4 In this case the orbital contribution is smaller than in the p^ -polymorph. All cobalt(U) porphyrins and phthalocyanines and their five- or six-coordinate adducts are low spin except for (3-pic)CoPc which exhibits both high and low spin forms.5a'5c For example, the magnetic moments of (py)CoPc and (py)2CoPc are 2.03 and 1.90 B.M. respectively; the ESR spectra (gj. = 2.2, gH = 2.0 at 113 K) are consistent with a low spin form and show the unpaired electron to be in the ai g orbital.5a The high spin (3-pic)CoPc species has a magnetic moment of 4.89 B.M. at room temperature, the ESR spectrum (at 77 K) showing three g values, gi=5.55, g2=2.78, g3=1.54.5b It is suggested that some "special interactions" occur that increase the axial interaction (and/or decrease the in-plane interaction) so that the high spin form is favored-5d Whether the (3-pic)CoPc complex is low or high spin depends on the method of preparation (see Section 1.1 also). VI. 2. Results and discussion The variation of the magnetic susceptibility of CoTNPc with temperature was measured; the results are plotted in Figures IV. 1 and IV.2. The temperature variation of the magnetic moment is shown in Figure rv.3. The errors in magnetic susceptibility measurement are estimated to be 4% for the vibrating sample magnetometry (VSM) and 6% for the Gouy method (errors not shown in Figures IV. 1 and IV. 2). The raw data are listed in Appendix HI. The diamagnetic susceptibility of the ligand (the tetraneopentoxy-phthalocyanine dianion) is estimated from Pascal's constants6 and found to be -538 x 10"6 cm3 moH. The magnetic moment is calculated from the equation u. = 2.83 VxmT. The room temperature magnetic moment of CoTNPc in benzene solution is found to be 2.5 ±0.3 B.M. using the Evans method,7 which is in fair agreement with the value of 2.23 ± 0.08 B.M. determined in the solid-state using the Gouy balance. Therefore, this compound is low spin both in the solid state or in solution; the electronic configuration is shown in Figure IVA 8 The magnetic moment of the (py)CoTNPc complex is found to be 2.6 ± 0.3 B.M. in toluene solution using the Evans method, indicating this five-coordinate complex is low spin also. The small difference in magnetic moments for CoTNPc in the solid state and in solution may be due to experimental error (e.g., sample packing error in the Gouy method). Other possible sources of the difference may be some interactions in solution between the aromatic solvent and the complex (discussed in next chapter), while in the solid state an aza nitrogen could weakly coordinate to the nearby cobalt center.4 T(K) Figure IV.l. Variation of magnetic susceptibility with temperature for CoTNPc. E >< Figure IV.2. Variation of 1/Xm with temperature for CoTNPc. 2.4 1.2 H • 1 1 1 1 1 0 100 200 300 T(K) Figure TV3. Variation of the magnetic moment with temperature for CoTNPc. Z E e^Vaf b2 H d x y 2 B 2 e4b2ai2 e \\ \\ ^ f L , (a) d-orbital energies (b) energy states Figure rV.4. Assumed d-orbital energy splitting and energy states for square-planar, low spin Co(U). Note that there is a slight discontinuity in the 77 K region where the susceptibility data were obtained using both the vibrating sample magnetometry and the Gouy method (Figures IV. 1 - VI.3). This non-overlapping region is believed due primarily to a thermostating problem using the vibrating sample magnetometer at the higher temperatures.* The measurements on the vibrating sample magnetometer were made starting at 31 K and then decreasing to 4 K; then the temperature was reset at 36 K, and measurements taken during a raising of the temperature to 82 K. The irregular pattern of magnetic moment changes from 31 to 41 K also indicate a thermostating problem. The magnetic moment of tetraneopentoxyphmalocyaninatocobaltfjl) decreases with the temperature, but this behavior does not follow the normal Curie-Weiss behavior in which the reciprocal of the magnetic susceptibility versus temperature is a linear plot. The abnormal behavior is possibly due to intermolecular spin interactions;9 this kind of magnetic exchange results in an antiferromagnetic interaction. That the magnetic moments decrease with temperature was also observed for high spin (3-pic)2CoPc, but no explanation was given. * •Personal communication from Dr. R. C. Thompson. The 1/Xm v*. T plot (Figure rV.5) gives a straight line from 4.3 to 50 K with a negligible value for the Weiss constant [Xm=C/(T+6)L i-e., 6=2.76 K. The negative intercept on the T axis indicates the anriferromagnetism for this complex. Figure IV.5. Linear plot of 1/Xm vs. T in the low temperature range. 41 References 1. B. N. Figgis and R . S. Nyholm, / . Chem. Soc, 338 (1959). 2. A. T. Casey and S. Mitra, In Theory and applications of Molecular Paramagnetism, E. A. Boudreaux and L. N. Mulay ed., John Wiley & Sons, New York, 1976, pl35. 3. R . A. Martin and S. Mitra, Chem. Phys. Lett., 3 , 183 (1969). 4. J. M. Assour and W. K. Kahn, / . Am. Chem. Soc, 87, 207 (1965). 5. (a) F. Cariati, D. Galizzilli, F. Morazzoni, and C. Busetto, / . Chem. Soc. Dalton Trans., 556(1975). (b) F. Cariati, F. Morazzoni, and C. Busetto, ibid., 496 (1976). (c) F. Cariati, F. Morazzoni, and M. Zocchi, Inorg. Chim. Acta, 14, L31 (1975). (d) F. Morazzoni, F. Cariati, and G. Micera, Spectrochim. Acta, 36(A), 867 (1980). 6. R . S. Drago, Physical Methods in Chemistry, N. B. Saunders Company, Philadelphia, 1977, p413. 7. (a) D. F. Evans, / . Chem. Soc, 2003 (1959). (b) D. F. Evans, J. Chem. Soc. Dalton Trans., 2588 (1973). (c) D. H. Live and S. I. Chan, Anal. Chem., 42, 791 (1970). 8. G. La Mar and F. A. Walker, / . Am. Chem. Soc, 95, 1790(1973). 9. C. J. O'Connor, In Progress in Inorganic Chemistry, S. J. Lippard ed., John Wiley & Sons, New York, 1982, vol. 29, p203. Chapter V Spectroscopic Data for Tetraneopentoxyphthalocyaninatocobalt(II) and Its Five-Coordinate Adducts V.l. Introduction; Literature *H NMR Data Only a few NMR data have been reported for phthalocyanine compounds (ligands or metal complexes) because of very low solubility of these compounds in organic solvents. The dilithium,1 zinc,1 silicon and germanium2 unsubstituted phthalocyanine complexes and the zinc TNPc complex3 have been studied. Some J H NMR spectra of iron and ruthenium phmalocyardne complexes with pyridine and tri(n-butylphosphine) and other axial ligands are reported.4 For example, in *H NMR spectra of (PBu3)2FePc, the benzo-proton peaks are found at 9.26 and 7.89 ppm, and the signals of the axial tributylphosphine protons are at 0.13 (2.5H), -1.11 (IH), and -2.08 (IH) ppm.4 Bis(4-methylpiperidine)-phthalocyaninatocobalt(IIl) chloride has been used to study ring current effects by comparison with data for cobalt(ITI) porphyrin complexes, the results indicating that the ring current in phthalocyanine is lower than those in tetraphenylporphyrin (TPP) and octaethylporphyrin (OEP).5 The *H NMR spectra of some monomeric L2MPC complexes (M = Ru, Fe, L = isocyamdes, 1,4-diisocyanobenzenes) and some bridged phthalocyanine polymers (M = Ru, Fe, bridging ligands = 1, 4-diisocyanobenzene, 1, 4-pyrazines) are reported.6 The Pc ring protons appear as a typical AA'BB' system at a low field centered around 9 and 8 ppm respectively due to the strong ring current of the heteroaromatic K-electron system. The protons of the axial ligands are in general shifted to a higher field with respect to the protons of the non-coordinated ligands.6 Recently, the structure of octa-n-undecoxy-phthalocyanine in the solid state and tiqmd-crystalline state has been studied by solid state 1 3 C NMR spectroscopy.7 The *H NMR spectrum of a cobalt(DI) tetrasulfonato-phthalocyanine complex with one axial methyl group has been reported.8 However, no NMR spectra of paramagnetic phthdocyaninatocobalt(IJ) complexes could be found in the literature. V.2. Proton NMR Spectra The NMR spectra for the four and five coordinate CoTNPc complexes synthesized in the present work are given in Figures V.l to V.8 and the NMR data are summarized in Tables V.l and V. 2 (Table V.2 is in Section V. 2. a). The labeling of aromatic protons on phthalocyanine ring is shown as following (because the a and a' protons are not resolved and appear under a single broad signal, the a and a' protons are simply referred to as a protons): The benzo-proton of CoTNPc are not observed in deuterated chloroform but are detected in benzene-d6 and DMSO-d6 (Figure V.l , Table 2; see Section V. 2. a). The benzo-, and the methylene- and methyl- protons of the substituents on the phthalocyanine are detected by lR NMR spectroscopy in benzene-d^  or toluene-ds (Figures V.2 - V.8) for systems with axial ligands. After adding the axial N-donor ligands (N-methylimidazole, pyridine, 4-picoline, 4-te^butylpyridine, piperidine), an O-donor ligand (tetrahydrofuran), and a P-donor ligand (triphenylphosphine), the benzo-protons appear as two very broad peaks centered around 12 -13 and 9-10 ppm. The aromatic ligand protons could not be observed for any of the axial ligands in the spectra of the isolated complexes; the protons of the triphenylphosphine of an in situ sample of (PPh3)CoTNPc are seen as expected N N N Table V.l. !H NMR data for five coordinate LCoTNPc complexes8 complex a-H chemical P-H shift (ppm) -OCH2- -CH 3 -CH 3 (axial ligand)' (py)CoTNPcb 10.6 - 14.6 8.4- 10.4 4.95, 5.12, 2.05 and — and 5.55 2.33 (N-MeIm)CoTNPcc 10.5 - 12.8 8.1 - 9.8 4.45 and 1.79 and -1.75 4.75 1.81 (4-pic)CoTNPcd 10.5 - 13.7 8.5 - 10.2 4.83 and 1.99 and -7.50 5.07 2.10 (4-93upy)CoTNPce 10.5 - 12.8 8.1 - 9.8 4.24 and 1.55 and -0.58 4.45 1.70 (pip)CoNTPcf 9.9- 12.3 8.3- 9.8 4.47 1.67 — (THF)CoTNPcg 7.8- 10.0 11.0 - 14.0 5.92 2.42, 2.48 — and 2.62 (PPh3)CoTNPch 10.6 - 14.3 8.4 -9.8 5.00 1.85, 1.95 ~ and 2.03 a. At room temperature, in air, and in deuterated benzene, except where noted. Aromatic protons of axial ligands were not observed in cases b - e. b. In toluene-dg, dissolved and sealed anaerobically. The concentration of (py)CoTNPc is 2.0 x lO"3 M. c. The concentration of (N-Melm)CoTNPc is 2.0 x 10"3 M. 8(0*3) far free N-Melm in CDCI3 is 3.72 ppm; C. J. Pouchert and J. R. Campbell, The Aldrich Library of NMR Spectra, volVTfl,p27. d. The concentration of (4-pic)CoTNPc is 2.0 x 10"3 M; 8CH3 for free 4-pic = 1.83 ppm. e. The concentration of (4-fBupy)CoTNPc is 1.6 x 10*3 M; 8CH3 for free 4-*Bupy = 1.05 ppm. f. In CDCI3, the concentration of (pip)CoTNPc is 2.1 x 10-3 M; signals not seen for pip. g. The concentration of (THF)CoTNPc is 1.3 x 10"3 M, signals not seen for THF. h. An in situ sample. The total concentration of CoTNPc is 3.1 x 10'3 M and the total concentration of triphenylphosphine is 3.7 x 10"2 M. i. Signal results from exchange between coordinated and free N-donor ligand (see text). (c) (b) (a) l | N I I | l l l l | l l l l | l l l l | l | | | | | | | | | l l | | | [ | | | | | | | | | | | | | 16 14 12 10 8 6 4 2 PPM 0 Figure V. l . Room temperature lH NMR spectra of CoTNPc in different solvents: (a) chloroform-di, (b) benzene-ag, (c) DMSO-d6. S = non-deuterated solvent signal. X = impurities, also seen in the free ligand spectrum. s a - H | * - H H2O -CH3-\ -OCH2. If JUi 1 | i i t t | i i i i | 1 i 20 15 10 1 1 1 » 1 1 J 1 1 1 1 J 5 0 PPM -5 Figure V.2. Room temperature *H NMR spectrum of (py)CoTNPc in toluene-ds. S = non-deuterated solvent signal. X = impurities, also seen in the free ligand spectrum. H20 a-H P-H \ \ / -oau i x N I ~| I i r I | I 1 I T | f 1 I I f I I I I | f I I T | I T 1 T | I I I > f F I T T | f T r T f I i r rj r I T I T 1 » I I | 1 F f I | I I I I | I I T t | I I I I | I I I I | I I 14 12 10 8 B 4 2 0 - 2 PPM Figure V.3. Room temperature *H NMR spectrum of (N-methylimidazole)CoTNPc in benzene-de. S = non-deuterated solvent signal. X = impurities, also seen in the free ligand spectrum. Figure V.4. Room temperature *H NMR spectrum of (4-picoline)CoTNPc in benzene-dg. S = non-deuterated solvent X = impurities, also seen in the free ligand spectrum. Figure V.5. Room ternperature !H NMR spectrum of (4-rm-butylpyridine)CoTNPc in benzene-ds. S = non-deuterated solvent signal. X = impurities, also seen in the free ligand spectrum. Figure V.6. Room temperature *H NMR spectrum of (piperidine)CoTNPc in cWoroform-d. S = non-deuterated solvent signal. X = impurities, also seen in the free ligand spectrum. H20 r r r r T r r p r t n j r r r r r 16 14 i r n i T"j n n T n IT [TTTTJTTTTTTI n-rTTTT7T rrrj I i l l 111 M 111111 M 1111111 12 10 B 6 4 2 0 PPM Figure V.7. Room teniperarure lH NMR spectrum of (THF)CoTNPc in benzene-d6. S = non-dueterated benzene signal. X impurities, also seen in the free ligand spectrum. r PPhj Figure V.8. Room temperature ! H NMR spectrum of (Ph3P)CoTNPc formed in situ with excess PI13P in benzene-d6. S non-deuterated solvent signal. X = impurities, also seen in the free ligand spectrum. (Figure V.8). The methyl protons of the methyl substituted axial ligands are observed in upfield regions (Figures V.3 - V.5). The equilibrium constants discussed in Chapter HI illustrate that about 10 to 20 % of LCoTNPc (L = N-donor ligands) dissociates at the NMR concentrations used, and the positions for these methyl protons are the result of fast chemical exchange between the free and coordinated ligands on the NMR time scale; the positions of methyl resonances vary with the amount of the added axial ligands. The resonances of the protons on the phthalocyanine ring are also the result of fast chemical exchange between the four- and five-coordinated species. The spectra shown in Figures V.2 - V.7 are obtained from the solutions made with the isolated five-coordinated species. In the case of (4-pic)CoTNPc, two signals are observed in the upfield region (-2.0 and -7.5 ppm, Figure V.4). When some 4-picoline ligand is added, only one signal is observed and it is downfield relative to the two initial signals. For example, when the ratio of the total concentration of 4-picoline to the total concentration of Co species is 6.0, the signal of the methyl group appears at -0.07 ppm, as a result of fast chemical exchange between the coordinated and free ligand. The signal for the methyl group of the coordinated ligand is estimated be at -10.0 ± 1.0 ppm on the basis of the equilibrium constant for ligand binding at room temperature (1.3 x 104 M_ 1) obtained from UV-visible spectroscopy in toluene; when the ratio of the total concentration of 4-picoline to the total concentration of Co species is 11, the signal of the methyl group appears at 0.77 ppm, now consistent with the signal of the methyl group of the coordinated ligand being at -10.1 ± 1.0 ppm. So the signal of the methyl group of the coordinated ligand is estimated from both set of data to be at -10 ppm. Under the conditions of a system with 1:1 (4-pic)/CoTNPc (as for the isolated sample), the signal of the methyl group is calculated to be at -7.8 ±1.0 ppm, and so the obtained signal at -7.5 ppm is for the methyl group of 4-picoline. The other signal at -2.0 ppm is possibly due to coordinated water or other unknown impurities. As excess 4-picoline ligand is added, the signal at -2.0 ppm disappears, suggesting that any coordinated water molecules (or other unknown impurity ligands) are being substituted by the stronger ligand (4-picoline). In a similar fashion, the signal of the methyl protons of 4-fe^butylpyridine shifts downfield upon addition of more 4-ferf-butylpyridine (Figure V. 9). The signal of coordinated 4-rm-butylpyridine is estimated to be at -0.90 ±1.0 ppm from a calculation when no excess ligand is added, at -1.22 ± 1.0 ppm when the ratio of the total concentration of the axial ligand to Co is 4.6, and at -1.52 ± 1.0 ppm when the ratio of the total concentration of the axial ligand to Co is 8.2; thus the signal of the methyl of the coordinated axial ligand should be in the region of ~ -1.2 ppm (average of the three calculations). The error could come from the fact that the solvent signal used as the internal standard is affected by the presence of the paramagnetic species CoTNPc and (4-*Bupy)CoTNPc. The origins of the small broad peaks in the NMR spectra of (py)CoTNPc and (pip)CoTNPc at 3.5 ppm (Figures V.2 and V.6) are not known, and are considered to be due to unknown impurities. When an anaerobic (py)CoTNPc solution is exposed to oxygen at room temperature, no changes are observed in the NMR spectrum measured at -19.2 °C. For a cobalt(II) porphyrin, the binding of oxygen causes the unpaired electron to shift from cobalt(IT) to the bound C*2 molecule, and so the peaks in NMR spectrum become sharper; for example, the protons of the C-7 chain in [Co(AzpivpP)]* resonate in a narrower range •[Co(Azpivpp)]: A (0 (b) (a) 111111111111111111111111111111111111111111111111111111111111111111111111111111111111 14 12 10 8 6 4 2 0 PPM -2 Figure V.9. Room temperature *H NMR spectrum of CoTNPc and 4-*Bupy in C6D6 with [4-fBupy]t / [CoTNPc]t (a) 1:1, (b) 4.6:1 (c) 8.2:1. S = non-dueterated benzene signal. ON and are shifted downfield when the oxygen adduct is formed;9 the pyrrole proton resonances also sharper considerably. The lack of change in the NMR spectra suggests that oxygen does not bind to tetraneopentoxyphmalocyarrinatocobalt(II) in presence of an the axial pyridine, even though the axial base and low temperature are known to facilitate such oxygen binding.10 V.2.a. Solvent Effects Although CoTNPc had first been synthesized some six years ago, no NMR spectra of this paramagnetic complex were reported.3 The CoTNPc NMR data in an aromatic solvent (benzene-d6), a chlorinated solvent (chloroform-di), and a stronger coordinating solvent (DMSO-de), are reported here in Table V.2, and the spectra are shown in Figure V. l . Table V.2. The IH NMR data for CoTNPc in different solvents3 solvent benzo-protons chemical shift (ppm) -OCH2- -CH 3 CDCI3 not observed 5.2 -6.8b 2.60, 2.80 Q>D6 ~ 8.4 -10.2b 4.8 - 6.6b 2.65, 2.53, and 2.47 ~ 11.2-13.8b (CD3)2SO ~ 9.0 to 10.4b, 4.55 1.69 ~ 10.7 to 13.2b a. At room temperature. b. Very broad. 58 There are major differences between the lH NMR spectra in the three solvents (Figure V.l). The benzo-proton signals appear only in DMSO-d<5 and benzene-dg, and the signals for methylene and methyl are sharper in these solvents also. The methyl protons are further upfield shifted in DMSO than in the other solvents. The resonance of the methyl protons appears as three peaks in benzene solution, indicating a possible interaction between the solvent and the phthalocyanine ring. That the benzo-proton signals of CoTNPc are not observable in deuterated chloroform is probably due to the stronger a derealization (relative to a cobalt porphyrin) dominating the spin transfer11 and making these ring proton signals extremely broad. However, upon addition of a N-donor ligand (Table V. 1) or DMSO (probably as a S-donor12), broad benzo-proton peaks are observed and shifted downfield relative to those of the free TNPc ligand (Section II. 3) which are consistent with slightly weaker o delocalization.11 Solvent effects in such NMR spectra are expected considering the sensitivity of crystal field and spin-orbit coupling to solvation phenomena. The energy gap AE (ai - e), between the d z2and dxz, d y z orbitals in a square-planar arrangement (see Figure IV.4) controls the rate of electron spin relaxation via spin-orbital coupling.13 Hence, the electron spin-lattice relaxation time (Tie) will increase with increasing AE (ai - e), and therefore the proton NMR line width will increase with AE (ai - e).13 It has been noted that the interaction between aromatic molecules and four-coordinate Co(II) porphyrin complexes occurs at the periphery of the porphyrins ligands,13 and as a consequence, the separation between 2 E and 2 A i decreases, which makes the electron relaxation more efficient. Thus the resonance is less broadened in deuterated benzene than in CDCI3. For a four-coordinate the low spin cobalt(II) porphyrin, axial solvation of Co(II) will give rise to an interaction between dz2 and the appropriate solvent molecular orbital, thereby raising the energy of the dz2 orbitaL13d As a consequence, the separation between 2 E and 2 A i increases, the electron relaxation becomes less efficient, and so the resonances are broadened. This is probably the case for CoTNPc in chloroform-di. Also, the observed chemical shift of the pyrrole protons of CoTPP in DMSO-dg is significandy upfield (and broader), compared with the data in chloroform-di.14 In the case of the lH NMR spectra of CoTNPc in DMSO-d6, the corresponding benzo-proton signals are observed and almost at the same position as those found that in benzene, while in CDCI3 these signals disappear. It is not clear why the stronger DMSO ligand does not cause stronger axial solvation and make the signals broader in the case of CoTNPc in DMSO-dg. V.2.D. Multiplicities The NMR spectra of diamagnetic Li2Pc and ZnPc also show the two kinds of ring protons,1 a- and p*-protons, both of them being in the low field region where aromatic protons usually appear.15 These two peaks of the ring protons show the same splitting pattern (a pair of AA'BB' doublets) in the spectra of Li2Pc and ZnPc.1 The signals for the a- and p-protons in zinc (IT) tetramemylphthalocyanine split into two peaks with different intensities.1 In the case of (py)CoTNPc in toluene-ds at -19.9 °C, the P benzo-proton resonances appear as four peaks; with increasing temperature, each of these four peaks further splits into two peaks (Figure V.10 .a). With increasing temperature, the proton signals of the methylene and methyl groups also change and split into at least four and five peaks, respectively (Figures V.lO.b and V.lO.c). This splitting cannot result from any dynamic equilibrium between the four-and five-coordinate species, which must be fast at all the temperatures examined. The square-planar cobalt(II) complex can exist in four possible isomers, which differ in the relative positions of the four neopentoxy substituents on the periphery of the phthalocyanine, and these isomers give rise to a total of eight possible environments for the P-protons;3 i.e., the protons at the P positions are not chemically and magnetically the same. Furthermore, in five-coordinate complexes, the adding of the fifth axial ligand could < r t - t i - r r r | I / . " r-r i -r-r r T 1 " 1 " r T r ' • » r j t r r-t i « t , T i i i i i | n i i | r t-» t f-r-t-r i - T T r t-1 i-r-r i r-t-r » " iS 1? II 10 T T T 1 7 1 -Figure V.10.a. *H NMR spectra of the benzo-protoris for (py)CoTNPc at various temperatures in toluene-dg. -A - 40.0 *C A 29.2 *C 19.9 *C 6.3 *C -4.2 *C 19.9 *C ' | 'MI | l l l l |MM|Mlr | l l t l | I IM| I I I I | IMI | l l l l | IMI | l l i r ) l l l l |MI I | l l l l l l l l l | l l l l | l l l l | l | l | | l | | | | | (M[ I IM| IMI | l 3.8 3.6 3.4 3 ? 3 0 2 fl 2.6 2 4 2.2 2.0 1.8 PPH.B Figure V.lOx. lH NMR spectra of the methyl protons for (py)CoTNPc at various temperatures in toluene-ds. create chiral centers. Some signals of these P-protons may overlap, which would result in about four peaks for the p-protons of (py)CoTNPc at room temperature, and more at higher temperature. Raising the temperature narrows the linewidths, and allows for resolution of more signals. The splitting patterns of the a- and p^ -protons could also result from the distortion of the macrocycle which makes the protons at the four benzo-rings different. The low temperature ESR spectrum of high spin (3-pic)CoPc has three signals: gi=5.55, g2=2.78, g3=1.54, which means that there is distortion of the macrocycle;16 the crystal structure of bis(4-methylpyridine)phthalocyaninatocobalt(II) shows that one of the N-Co-N angles in the macrocycle plane is larger than 90° while the other three angles are smaller. This supports the argument that the macrocycle is distorted in the solid state. In the case of CoTNPc in aromatic solvents, the CoTNPc macrocycle could possibly be distorted by interactions between the complex (at the Pc ring) and solvent molecules. V.2.c. Isotropic Shift For low spin Co(U) porphyrins, the isotropic shifts have been shown to be due mainly to a dipolar shift (through space), with the contact shift (through bond) being small.11 Because the electronic ground state of a square-planar low spin Co(U) is 2 A i (dz2)1 and the dz2 orbital is expected to interact weakly with the a system of the phthalocyanine ligand, the majority of the isotropic shift in the CoTNPc species is expected to result from the dipolar interaction. All shifts for the a-and p-protons, methyl and methylene protons are shifted downfield from their diamagnetic protons, which is consistent with the dipolar and a contact shift.13d The disappearance of the signals of the aromatic protons of the axial ligand and the downfield shift of the alkyl group on the axial ligand are also consistent with a a-spin delocalization mechanism involving the singly occupied d z 2 . 1 3 d The upfield shifts of methyl protons of the axial ligands are mainly due to the aromatic ring current of the phthdocyanine, but the broadness of the signal indicates chemical exchange between the free and coordinated ligands, and a contribution from a dipolar interaction as well. Although the various Curie plots [(AH/H)iso vs. 1/T] are linear, the extrapolated isotropic shifts at infinite temperature are not zero (Figure V.ll). The diamagnetic reference used is tetraneopentoxyphthalocyanine (H2TNPC). The linearity of the isotropic shift of the benzo-protons against inverse temperature and the positive slope are indicative of a contact contribution, while the non-zero intercept is consistent with the dipolar interaction.13d Because of the distance of the methylene and methyl groups to the metal centre, no contact contribution to the isotropic shifts is expected, so the slopes of their temperature dependent behavior are opposite to that of the benzo-protons, and the intercept is again nonzero. V.3. Deuterium NMR (observation of an axial pyridine ligand) The usual relaxation mechanisms in NMR involve magnetic interactions between the nucleus and its environment. The relaxation times are proportional to the square of gyromagnetic ratio, thus the linewidths of J H lines may be 42.5 times greater than those of D lines.17 The paramagnetic shift is proportional to the gyromagnetic ratio, and the resolution of the 2H spectrum is 6.5 times better than that of the *H spectrum of the same compound. Therefore, deuterium signals are much more readily detected than corresponding proton signals when severe paramagnetic broadening is apparent. The 2 H NMR spectrum of py-ds in a CoTNPc system with a molar concentration ratio of 17:1 ([py-dsMCoTNPc]) results from rapid exchange between the coordinated and the free pyridine on the deuterium NMR time-scale (Figure V.12). The common labeling system for pyridine is shown below: 65 25 \5 o -OCH2-A -CH 3 -D benzo-H 05 0.000 0.001 0.002 0.003 0.004 1/T(1/K) Figure V. l l . Curie plot of (py)CoTNPc in toluene-d8; the revelant spectra are given in Figure V. 10. a - c; the diamagnetic reference was H2TNPC, 8(benzo-H) centered at 7.85 ppm, 5(CH2) centered at 4.05 ppm, 6XCH3) centered at 1.40 ppm (see Figure ELI) Figure V.12. Room temperature 2 H NMR spectra of pyridine-ds (a) with and (b) without CoTNPc. Y P N ^ According to the intensities and comparison with the literature,18 the peaks are assigned as shown in Table V.3: Table V.3. Deuterium NMR data for pyridine-ds in a toluene solution of CoTNPca compounds a-D chemical shift (ppm) p-D y-D py-ds 9.70(27 Hz) 7.91(18 Hz) 8.23(22 Hz) (py-d5)CoTNPC 12.10(283 Hz) 8.50(90 Hz) 7.22(45 Hz) +py-d5b a. In toluene, at room temperature. Numbers in parentheses are linewidths at half height in Hertz. b. The total concentrations for Co species and pyridine-ds are 2.5 x lf>3 M and 4.2 x 10"2 M, respectively. On the basis of the equilibrium constant of 5.0 x 103 M"1 for pyridine binding, obtained by UV-Visible spectroscopy at this temperature, the pyridine signals in Figure V. 12 represent approximately 94% of free pyridine and 6.0% coordinated pyridine. Presumably these are the mole-fraction weighted signals17 with respect to two forms of pyridine, and the "limiting" chemical shifts values for the coordinated pyridine are calculated as 49.8 ± 1.0 ppm (a-deuterium), 12.7 ± 1.0 ppm (pV-deuterium), -3.6 ± 1.0 ppm (Y-deuterium). The opposite shift directions for the ortho and meta versus para protons indicate there is n spin density of the unpaired electron on the axial ligand. As the unpaired electron is assumed to be in the d z 2 orbital of the metal ion which is of the proper symmetry to delocalize into the a system of the axial ligand, any spin density in the TC orbital of these ligands must be introduced via an indirect mechanism, i.e., polarization of the TC electronic system by the a electrons.19 The linewidths of the signals of pyridine-ds; a-D > |5-D > •y-D reflect the distances of these deuterium atoms from the paramagnetic ion center.20 V.4. Phosphorus-31 NMR and Proton NMR Spectra of in situ (PPh3)CoTNPc. Attempts were made to measure the 3 1 P NMR spectra of solutions of CoTNPc (3.1 mM) in deuterated benzene with added concentrations of triphenylphosphine ranging from 37 mM to 63 mM. No signals could be detected. This must be due to extreme broadness of the signals. No free ligand signals at -6.05 ppm were observed even when the concentration of the ligand was ten-fold over that of the CoTNPc. The proton NMR (Table V.4) spectra were obtained using the same samples (Figure V. 13). Table V.4. Proton NMR data for the axial ligand of (PPh3)CoTNPca compound chemical shift (ppm) o-H m-H p-H PPh3 7.41 - 7.35(m) 7.05 - 7.02(m) 7.05 - 7.02(m) PPh3/CoTNPcb 6.85(s) 7.26(s) 6.52(s) PPh3/CoTNPcc 7.03(s) 7.19(s) 6.68(s) a. At room temperature in benzene-d6. Letters in the parentheses indicate the multiplicities of the peaks. b. The total concentration of PPI13 is 3.7 x 10"2 M, the initial concentration of CoTNPc is 3.1 x 10-3 M . c. The total concentration of PPI13 is 6.3 x lf>2 M, the initial concentration of CoTNPc is 3.1x10-3 M. The peaks are simply assigned on the basis of intensities, and the fact that the ortho resonance is expected to be broadest since this proton is closest to the paramagnetic ion. The two resonance peaks for the free ligand triphenylphosphine display multiplet structure. Because of the fast exchange between the coordinated and free triphenylphosphines on the NMR time-scale, there is only one set of resonances for the phenyl protons which is the weighted average of the two kinds of triphenylphosphine. Assuming under the conditions for (b) and (c) in Fig. V.13 that near 100 percent of CoTNPc is coordinated by PPh3, the coordinated m-H resonance is estimated to be at ~ 10 ppm while the o-H and p-H should be at ~ 0 ppm, using data from both spectra. The opposite shift direction on coordination for the o-H and p-H versus m-H suggests that the contact shift results from the spin transfer via phosphorus to the phenyl groups. The cobalt complex exhibits upfield shifts for the ortho and para protons and a downfield shift for the meta proton indicating that the observed shifts are primarily due to the contact shift with unpaired spin in n orbitals of the phosphine ligand. The resonance of the para proton of the coordinated triphenylphosphine is shifted almost as much as that of the ortho protons (150 and 162 Hz, respectively), so that any contribution from unpaired electron spin in the a system must be negligible. Figure V.13. Room temperature *H NMR spectra of PPI13 in CoTNPc solution, (a) free PPly. (b) PPh3 (~ 37 mM) containing CoTNPc (~ 3.1 mM); same as Figure V. 8. (c) PPI13 (~ 63 mM) containing CoTNPc (~ 3.1 mM). 71 The phenyl resonance peaks are too broad to resolve the small intraphenyl spotting because of the interaction of the proton nuclei with the unpaired electron of the metal ion. The phenyl proton spin is relaxed sufficiently fast, and cannot cause any splitting of the resonances of nearby protons. The proximity of the protons to the paramagnetic center decides the linewidth of these resonance peaks. V.5. ESR Spectra Both CoTNPc and (py)CoTNPc were ESR silent in toluene glass at 77 K. The absence of ESR signals and relatively sharp NMR resonances indicate short electronic relaxation times. Although an ESR spectrum has been obtained for the binuclear cobalt tetraneopentoxyphthalocyanine, with mixed valence Co(U) and Co (I) centers, linked by a 1, 8-naphthalene group (Nap), NaptC^TrNPcCo^rNPc]-, and containing axially coordinated 2-methylimidazole, no signals were observed for the parent Co(II)-Co(II) species* or its one-electron reduced form Nap[CoIITrNPcCoITrNPc]-.21 Unlike for other cobalt(U) phthalocyanines systems,22-24 no signal was observed also for CoTNPc or its monopyridine adduct in toluene at 77 K under an atmosphere of O2. The data are consistent with nonformation of dioxygen complexes (see Sections Ul. 3, V. 2, V. 6). V.6. Infrared Spectra The infrared stretching values have been reported for O2 bound to cobalt(H) •NapIConTrNPcConTrNPc]: porphyrin10 and salen25 complexes, as well as, for example, to iron(II), and to manganese(II) porphyrins26 and manganese(II) phthalocyanine27. The 1:1 dioxygen complexes with v(02) values between 1100 and 1200 cm-1 have the dioxygen bonded (as superoxide) in an end-on (terminal) bent configuration (Figure 14,1)*, whereas those with (O-O) stretches between 800 and 950 cm*1 have the dioxygen bonded (as peroxide) in a side-on, triangular, symmetric manner (Figure 14, H).10>26 For bridging peroxide and superoxide complexes of 1:2 O2/C0 stoicbiometry (Figure 14. IH), the stretching vibrations are in the 800 to 950 cm*1 and ~ 1100 cnr1 regions, respectively.27 However, it is possible that no IR band attributable to a coordinated O2 group is observed, because a centrosymmetric arrangement such as in Figure 14. HI could lead to a substantially IR inactive O-O stretching vibration.25*28 For example, no differences between the IR spectra of [Co(salen)py]02 and Co(salen)py2 are found.29 O Co o 0 = o — Co — L — Co-O — Co — L n m Figure V.14. Configurations of coordinated dioxygen in metalloporphyrin and metallophthalocyanine dioxygen adducts; formal oxidation states of the O2 and Co centers are not presented. * A unique example of a side-on bonded superoxide moiety at cobalt has been demonstrated recently; E. K. Byrne and K. H. Theopold, / . Am. Chem. Soc, 109, 1282 (1987). The elemental analysis of the (py)CoTNPc complex suggests that one molecule of this complex may bind one dioxygen when exposed to air (see Section II.4 ), but on comparing the infrared spectrum of "isolated (py)CoTNPc" with that of CoTNPc (Figure V.15), no bands for the stretching vibration of dioxygen could be found. Combining these IR data and the results of the UV-visible, ESR and NMR spectral studies, it is concluded that (py)CoTNPc does not bind oxygen at ambient or low temperatures. This pyridine complex is probably hygroscopic. However, considering the possibility of overlap of bound dioxygen stretching vibrations with some vibrations of (py)CoTNPc, oxygen-18 isotope infrared spectroscopy and/or Resonance Raman spectroscopy could be done to confirm the non-interaction with O2. Figure V.15. The infrared spectra of CoTNPc and (py)CoTNPc (KBr pellets). (py)CoTNPc I 1 1 1 1 1200. o 1100. o 1000. o ooo. oo aoo. oo W A V E N U M B E R S CCM-1> References 1. T. B. Marks and D. R. Stojakovic, / . Am. Chem. Soc., 100, 1695 (1978). 2. (a) J. N. Esposito, J. E. Lloyd, and M. E. Kenney, Inorg. Chem., 5, 1979 (1966). (b) J. N. Esposito, L. E. Sutton, and M. E. Kenney, ibid. 6, 1116 (1967). (c) A. R. Kane, R. G. Yalman, and M. E. Kenney, ibid. 7,2588 (1968). 3. (a) C. C. Leznoff, S. M. Marcuccio, S. Greenberg, A. B. P. Lever, and K. B. Tomer, Can. J. Chem., 63, 623 (1985). (b) S. M. Marcuccio, P. I. Svirskaya, S. Greengerg, A. B. P. Lever, C. C. Leznoff, and K. B. Tomer, Can. J. Chem., 63, 3057 (1985). 4. M. M. Doeff and D. A. Sweigart, Inorg, Chem., 20, 1683 (1981). 5. R. J. Abraham and C. J. Medforth, Magn. Reson. Chem., 26, 803 (1988). 6. (a) M. Hannack, S. Deger, and A. Lange, Coord. Chem. Rew., 82, 115 (1988). (b) M. Hannack, A. Hirch, and H. Lehmann, Angew. Chem. Int. Ed. Engl., 29, 1467 (1990). 7. A. P. M. Kentgens, B. A. Markies, J. F. van der Pol, and R. J. M. Nolta, / . Am. Chem. Soc., 112, 8800 (1990). 8. P. Day, H. O. A. Hill, M. G. Price, / . Chem. Soc. (A), 90 (1968). 9. Y. Uemori and E. Kyuno, Inorg. Chim. Acta, 174, 109 (1990). 10. B. R. James, In The Porphyrins, D. Dolphin ed., Academic Press, New York, 1978, vol. V, p201. 11. (a) H. M. Goff, G. La Mar, and C. A. Reed, / . Am. Chem. Soc, 99, 3641 (1977). (b) H. M. Goff and E. Shimomura, / . Am. Chem. Soc, 102, 31 (1980). 12. F. Calderzzo, S. Frediani, B. R. James, G. Pampaloni, K. J. Reimer, J. R. Sams, A. M. Serra, and D. Vitali, Inorg. Chem., 21, 2302 (1982). 76 13. (a) G. La Mar and F. A. Walker, / . Am. Chem. Soc, 95, 1790 (1973). (b) G. P. Fulton and G. La Mar, J. Am. Chem. Soc, 98, 2119 (1973). (c) G. P. Fulton and G. La Mar, / . Am. Chem. Soc, 98, 2124 (1973). (d) G. N. La Mar and F. A. Walker, In The Porphyrins, D. Dolphin ed., Academic Press, New York, 1978, vol. IV(2), p61. 14. N. J. Clayden, G. R. Moore, R. J. P. Williams, J. E. Baldwin, and M. J. Crossley, / . Chem. Soc Perkin Trans. II, 1863 (1983). 15. A. B. P. Lever, Adv. Inorg. Chem. Radio chem., 7, 82 (1965). 16. F. Cariati, F. Morazzoni, and C. Busetto, J. Chem. Soc. Dalton Trans., 1976, 496 (1976). 17. (a) B. R. McGarvey and R. J. Kurland, In NMR of Paramagnetic Molecules, G. N. La Mar, W. D. Horrocks, and R. H. Holm, eds., Academic Press, New York, 1973, Chapter 14. (b) T. J. Swift, ibid. Chapter 2. 18. A. Shirazi and H. M. Goff, Inorg. Chem., 21, 3420 (1982). 19. J. A. Happe and R. L. Ward, J. Chem. Phys., 39, 1211 (1963). 20. (a) R. D. Arasasingham, A. L. Balch, C. R. Cornman, and L. Latos-Grazynski, / . Am. Chem. Soc, 111, 4357 (1989). (b) R. D. Asarasingham, A. L. Balch, R. L. Hart, and L. Latos-Grazynski, J. Am. Chem. Soc, 112, 7566 (1990). 21. (a) N. Kobayashi, H. Lam, W. A. Navin, P. Janda, C. C. Leznoff, and A. B. P. Lever, Inorg. Chem., 29, 3415 (1990). (b) C. C. Leznoff, H. Lam, N. A. Navin, N. Kobayashi, and P. Janda, Angew. Chem. Int. Ed. Engl, 26, 1021 (1987). 22. E. R. Milaeva, Z. Szeverenyi, and L. I. Simando, Inorg. Chim. Acta, 67, 139 (1990). 23. (a) D. M. Wagnerova and K. Lang, Inorg. Chim. Acta, 162,1 (1989). 77 (b) L.D. Rollmann and S. I. Chan, Inorg. Chem., 10, 1978 (1971). 24. C. Busettto, F. Cariati, D. Galizzioli, and F. Morazzoni, Gazz. Chim. Ital., 104, 161 (1974). 25. M. Susuki, T. Ishiguro, M. Kozuka, and K. Nakamoto, Inorg. Chem., 20, 1993 (1988). 26. R. D. Jones, J. R. Budge, P. E. Ellis, Jr., J. E. Linard, D. A. Summerville, and F. Basolo, / . Organomet. Chem., 181, 151 (1979). 27. A. B. P. Lever, J. P. Wilshire, and S. K. Quan, / . Am. Chem. Soc, 101, 3668 (1979). 28. B. Bosnish, C. K. Poon, and M. L. Tobe, Inorg. Chem., 5, 1514 (1966). 29. C. Floriani and F. Calderzzo, / . Chem. Soc (A), 946 (1969). Chapter VI General Conclusions and Some Recommendations for Future Work In this thesis work, some five-coordinate tetraneopentoxyphthdocyarrinatocobalt(II) complexes (LCoTNPc, L = N-Melm, py, 4-pic, 4-*Bupy, pip, THF, DMSO) have been isolated and characterized by UV-vis spectroscopy, MS (FAB), and NMR spectroscopy; in situ species with L = Im, PPh3 have been studied also. The equilibrium constants for the binding of some of these ligands to Co(II)TNPc in toluene were measured at various temperatures, and the thermodynamic data, i.e., the enthalpies and entropies for these reactions, were estimated. The order of equilibrium constants for the ligand binding at room temperature is: N-Melm > pip > 4-rBupy > Im > py > THF. The equilibrium constant for THF binding and the corresponding exothermic enthalpy value are much smaller than those of the N-donor ligands. The magnetochemistry of CoTNPc was studied. The magnetic moment of CoTNPc in the solid state is 2.23 ± 0.10 B.M. at ambient temperature, while the magnetic moment is 2.47 ± 0.10 B.M. in toluene solution (determined by Evans' method). The magnetic moment of the five-coordinate species (py)CoTNPc is 2.61 ± 0.10 B.M. in toluene solution. Thus CoTNPc and the five-coordinate complex (py)CoTNPc at room temperature are low spin with one unpaired electron. Some antiferromagnetic behavior is found for the four-coordinate complex in the magnetic moment versus the temperature plot. The *H NMR spectra of the paramagnetic species (CoTNPc and LCoTNPc, L = Im, N-Melm, py, 4-pic, 4-*Bupy, pip, THF, PPI13) were studied. The *H NMR spectra of CoTNPc are found to be solvent dependent; the a- and p*-proton signals of the phthalo-cyanine ring are very broad in DMSO-d6 and benzene-ds, and in chloroform-di these signals are so broad that they could not be observed. The irregular multiplicities in these proton NMR spectra are attributed to the fact that these cobaltfjl) complexes are mixtures of isomers. The isotropic shift vs.l/T plot (Curie plot) of (py)CoTNPc shows that the 79 extrapolated isotropic shifts of the benzo-, methylene, and methyl protons on the phthalocyanine ring at infinite temperature are not zero, indicating that there is a contribution from a dipolar interaction. For the axial ligands, the proton signals of the methyl groups of some ligands (L = N-Melm, 4-pic, 4-fBupy) are observed, but these signals are averages due to rapid chemical exchange between the free and coordinated ligands; the aromatic proton signals of these ligands are not observed. However, the 2 H NMR spectra of the in situ (pyridme-d$)G>TNPc complex show that the y-2!! signal shifts in a direction different to those of the a- and p^H signals, suggesting that a contact shift mechanism is dominant in this case. The 3 1 P NMR spectra of in situ samples of PPI13 with CoTNPc do not give any peaks, indicating that signals for the phosphine are extremely broad; the *H NMR spectra of the same samples give the signals for the axial phenyl protons, this observation suggesting that an interaction between the unpaired electron on the cobalt and the phenyl protons occurs through a contact mechanism. Finally, elemental analyses, UV-visible spectra, IR, NMR, and ESR results suggest that CoTNPc and its five-coordinate species do not bind oxygen at ambient or subzero temperatures. Some of this work could be extended, e.g., isolation of five-coordinate phosphine complexes; for the (DMSO)CoTNPc complex, it is not clear whether the DMSO is S- or O-bonded, and the ligand binding equilibrium constants in solution at several temperatures need to be measured. Although the cobalt(I) and cobalt(ni) tetraneopentoxyphthalocyanine could be generated by disproportionation in the presence of hydroxide ion or electro-chemically (see Section 1.3), these Co(I) and Co(IJJ) species have not been isolated, and it would be worthwhile to separate them and study their coordination chemistry, so a comparison with the Co(H) species could be made. The formation and characterization of a high-spin metal phthalocyanine complex are of interest both from a chemical point of view or from the biological implications; it is possible that high spin Co(II) phthalocyanine complexes could be prepared by refluxing the four-coordinate CoTNPc in a solvent ligand of time (see Section 1.1). The electrochemistry of the five-coordinate LCoTNPc compounds could be studied. Although the cobalt(JJ) complexes studied here do not bind oxygen, it has been reported that four-coordinate phthalocyaninatocobalt(II) can catalyze heterogeneously the autooxidation of a phenolic compound by oxygen (see Chapter I). The homogeneous catalytic oxidations of phenolic compounds, which are proposed as lignin models, should be explored by using CoTNPc complexes to mimic the ligninase. Appendix L Extinction coefficients for UV-vis spectra of CoTNPc in toluene at ambient temperature: Length of the cell = 0.50 cm; A = absorbance at X max values. Concn, 10*5 M A, at 673.5 nm A, at 607 nm A, at 333 nm 4.8 2.4 1.2 0.60 2.77 1.382 0.692 0.164 0.803 0.370 0.264 0.081 1.523 0.794 0.523 0.215 2 3 4 Concn, l(r 5 M B 673.5 nm o 607 nm A 333 nm Extinction coefficient at 673.5 nm = 12 x 10s M" 1 cm"1 Extinction coefficient at 607 nm = 3.3 x 104 M ' 1 cm*1 Extinction coefficient at 333 nm = 6.0 x 10* M' 1 cm*1 The behaviors of CoTNPc in UV-vis spectra in toluene in the concentration range (6.0 x 10"6 to 4.8 x 10"5 M) obey Beefs Law. Appentix EL Raw data and data analysis for the ligand binding to CoTNPc. n.l. Raw data and data analysis for the binding of imidazole to CoTNPc temp. = 9.0 *C, X = 673.5 nm, A 0 = 0.922, A * = 0.605, [CoTNPc] = • 7.7 x lO"6 M [Im],xl(r5M A c^orrect log ^ ° " ^ A - Aoo log[Im] 2.10 0.807 0.809 -0.275 -4.678 2.92 0.777 0.779 -0.085 -4.535 4.02 0.747 0.750 0.074 -4.396 5.43 0.720 0.723 0.227 -4.265 7.43 0.696 0.701 0.362 -4.129 10.3 0.671 0.678 0.524 -3.987 14.5 0.647 0.656 0.717 -3.839 slope = 1.2, log K = 4.452 temp. =21.0 *C, X = 673.5 nm, , Ao= 1.294, Aoo = 0.852, [CoTNPc] = l.lx lO-5 M [Im],x 10-5 M A c^orrect log [Im] 1.04 1.233 1.234 -0.804 -4.983 2.10 1.180 1.183 -0.475 -4.678 3.19 1.141 1.145 -0.294 -4.496 4.56 1.100 1.105 -0.127 -4.341 6.25 1.065 1.071 0.008 -4.204 8.78 1.025 1.031 0.167 -4.057 13.0 0.974 0.986 0.361 -3.886 19.2 0.927 0.944 0.580 -3.717 slope = 1.1, log K = 4.228 n.l. Raw data and data analysis for the binding of imidazole to CoTNPc (continued). temp. = 31.0 *C, X = 673.5 nm, AQ= 1.160, A«, = 0.756, [CoTNPc] = 9.6 x 10-6 M [Im],xl(r5M A Acorrect log [Im] 0.980 1.131 1.132 -1.128 -5.009 2.93 1.072 1.075 -0.574 -4.533 4.90 1.025 1.030 -0.324 -4.310 6.90 0.991 0.998 -0.174 -4.161 9.90 0.946 0.955 0.013 -4.004 13.9 0.905 0.917 0.179 -3.857 19.3 0.867 0.883 0.339 -3.714 slope = 1.1, log K = 4.016 temp. = 45.0 °C, A = 673.5 nm, An = 1.344, A « = 0.901, [CoTNPc] = 1.1 x lO"5 M [Im],x 10-5 M A c^orrect log [Im] 1.39 1.313 1.315 -1.155 -4.857 3.63 1.269 1.273 -0.719 -4.440 6.43 1.223 1.231 -0.465 -4.192 9.23 1.187 1.197 -0.304 -4.035 12.6 1.156 1.170 -0.189 -3.900 16.8 1.117 1.135 -0.049 -3.775 21.8 1.081 1.103 0.077 -3.662 27.9 1.045 1.073 0.197 -3.554 38.9 1.010 1.045 0.317 -3.410 49.6 0.965 1.011 0.402 -3.305 slope = 1.0, log K = 3.727 II.2. Raw data and data analysis for the binding of N-memylimidazole to CoTNPc. temp. = 9.0 *C, X = 673.5 nm, An= 1.464, A*, = 0.928, [CoTNPc] = : 1.2 x 10-5 M [N-Melm], xl0" 5M A c^orrected log [N-Melm] 0.140 1.399 1.399 -0.860 -5.854 0.374 1.311 1.312 -0.402 -5.427 0.705 1.205 1.207 -0.036 -5.152 1.17 1.160 1.162 0.111 -4.932 1.64 1.113 1.116 0.267 -4.785 2.16 1.089 1.092 0.356 -4.666 3.47 1.040 1.045 0.554 -4.460 slope = 1.0, log K = 5.038 temp. = 21.0 *C, X = 673.5 nm. , An = 0.744, A« = 0.463, [CoTNPc] = 6.2 x lO"6 M [N-Melm], xl0" 5M A c^orrected log [N-Melm] 0.930 0.648 0.649 -0.292 -5.032 1.70 0.606 0.607 -0.022 -4.770 2.76 0.576 0.578 0.159 -4.559 4.13 0.548 0.550 0.348 -4.384 5.78 0.528 0.531 0.496 -4.238 8.55 0.508 0.513 0.665 -4.068 slope = 1.0, log K = 4.737 112. Raw data and data analysis for the binding of N-memylimidazole to CoTNPc (continued). temp. = 31.0 *C, A, = 673.5 nm, Ao= 1.109, Aoo = 0.706, [CoTNPc] = 9.2 x 10-6 M [N-Melm], xlO-SM A Acocrected log [N-Melm] 0.190 1.067 1.067 -0.934 -5.721 0.633 1.013 1.014 -0.511 -5.199 1.65 0.952 0.954 -0.204 -4.783 3.21 0.892 0.895 0.054 -4.493 5.93 0.842 0.848 0.264 -4.227 9.22 0.805 0.813 0.442 -4.035 14.3 0.771 0.783 0.627 -3.845 slope = 0.8, log K = 4.569 temp. = 45.0 'C, X = 673.5 nm, An = 1.090, Aoo = 0.716 [CoTNPc] =  9.1 x lO"6 M [N-Melm], x 10-5 M A •^ corrected log [N-Melm] 0.579 1.053 1.054 -0.973 -5.237 1.77 0.994 0.996 -0.474 -4.752 4.24 0.921 0.925 -0.103 -4.373 8.08 0.874 0.882 0.098 -4.093 13.9 0.830 0.842 0.294 -3.857 22.4 0.797 0.815 0.444 -3.650 38.1 0.753 0.783 0.661 -3.419 slope = 0.9, log K = 4.189 EL3 Raw data and data analysis for the binding of pyridine to CoTNPc. temp. = 9 . 0 'C, X = 6 7 3 . 5 nm, Ao= 0 . 9 1 5 , A^, = 0 . 6 3 9 , [CoTNPc] = > 7 . 6 x 1 0 - 6 M [py], x 1 0 - 5 M A c^orrected log [py] 1 . 4 8 0 . 8 8 4 0 . 8 8 5 - 0 . 9 1 4 - 4 . 8 3 0 3 . 8 8 0 . 8 4 9 0 . 8 5 2 - 0 . 5 2 9 - 4 . 4 1 1 7 . 4 7 0 . 8 0 6 0 . 8 1 2 - 0 . 2 2 5 - 4 . 1 2 7 1 2 . 3 0 . 7 6 6 0 . 7 7 6 0 . 0 0 6 - 3 . 9 1 0 1 8 . 2 0 . 7 3 4 0 . 7 4 8 0 . 1 8 5 - 3 . 7 4 0 2 6 . 6 0 . 7 0 7 0 . 7 2 6 0 . 3 3 7 - 3 . 5 7 5 3 9 . 6 0 . 6 7 4 0 . 7 0 2 0 . 5 2 9 - 3 . 4 0 2 slope = 1 . 0 , log K = 3 . 9 1 3 temp. = 2 1 . 0 *C, X = 6 7 3 . 5 nm, , Arj = 0 . 6 4 2 , A©o = 0 . 4 4 7 , [CoTNPc] = 5 . 4 x 1 0 - 6 M [py], x 1 0 - 5 M A •^ corrected log [py] 2 . 9 2 0 . 6 1 4 0 . 6 1 6 - 0 . 8 1 3 - 4 . 5 3 4 6 . 1 5 0 . 5 8 9 0 . 5 9 2 - 0 . 4 6 2 - 4 . 3 0 9 1 1 . 0 0 . 5 6 3 0 . 5 6 9 - 0 . 2 2 3 - 3 . 9 5 9 1 7 . 4 0 . 5 4 1 0 . 5 5 1 - 0 . 0 5 8 - 3 . 7 5 9 2 6 . 0 0 . 5 1 9 0 . 5 3 3 0 . 1 0 3 - 3 . 5 8 5 3 8 . 5 0 . 4 9 6 0 . 5 1 6 0 . 2 6 2 - 3 . 4 1 5 5 6 . 5 0 . 4 7 2 0 . 5 0 0 0 . 4 2 8 - 3 . 2 4 7 slope = 0 . 9 , log K = 3 . 7 0 1 I L 3 . Raw data and data analysis for the binding of pyridine to CoTNPc (continued). temp. = 31.0'C, X = 673.5 nm, Ao = 0.734, Aoo = 0.520, [CoTNPc] = 6.1 x lO'6 M [py],x Hr 5 M A Acorected log [py] 1.28 0.723 0.724 -1.310 -4.893 5.15 0.699 0.703 -0.771 -4.288 10.3 0.673 0.680 -0.472 -3.987 16.6 0.649 0.660 -0.277 -3.780 24.1 0.624 0.640 -0.106 -3.617 32.7 0.603 0.623 0.032 -3.485 44.6 0.579 0.520 0.173 -3.351 slope = 1.0, log K = 3.509 temp. = 45.0 °C, X = 673.5 nm, Ao = 0.807, Aoo = 0.581, [CoTNPc] = 6.7 x lO'6 M [py],x 10-5 M A c^orrected log [py] 4.09 0.782 0.785 -0.967 -4.388 9.52 0.760 0.767 -0.667 -4.021 18.9 0.730 0.744 -0.413 -3.723 32.9 0.697 0.720 -0.203 -3.482 52.2 0.661 0.696 -0.015 -3.282 74.2 0.625 0.675 0.147 -3.130 119 0.572 0.581 0.357 -2.924 slope = 0.9, log K = 3.285 n.4. Raw data and data analysis for the binding of 4-picoline to CoTNPc. temp. = 11.0 *C, X = 673.5 nm, An = 0.898, Aoo = 0.617, [CoTNPc] = 7.5 x 10-6 M [4-pic], A Aconected log ^ ° " ^ A - Aoo log [4-pic] xlO* 5M 0.900 0.846 0.847 -0.654 -5.046 1.85 0.812 0.813 -0.369 -4.733 3.31 0.775 0.777 -0.121 -4.480 5.29 0.744 0.747 0.065 -4.277 8.30 0.712 0.719 0.244 -4.081 13.3 0.682 0.689 0.463 -3.876 20.9 0.659 0.670 0.638 -3.680 slope = 1.0, log K = 4.350 temp. = 21.0 'C, X = 673.5 nm, An = 1.469, Aoo = 1.020, [CoTNPc] = 1.2 x lO'5 M [4-pic], A c^orrected log [4-pic] x lO"5 M 3.24 1.329 1.333 -0.362 -4.489 4.92 1.286 1.291 -0.183 -4.308 8.36 1.230 1.239 0.021 -4.078 11.8 1.287 1.199 0.179 -3.928 17.0 1.144 1.160 0.344 -3.770 23.8 1.113 1.135 0.463 -3.623 37.5 1.072 1.105 0.632 -3.426 slope = 0.9, log K = 4.112 II.4. Raw data and data analysis for the binding of 4-picoline to CoTNPc (continued). temp. = 31.0 *C, X = 673.5 nm, An = 1.082, Aoo = 0.756, [CoTNPc] = 9.0 x 10-6 M [4-pic], xlO-SM A Acorected log [4-pic] 1.70 1.046 1.047 -0.920 -4.770 5.14 0.989 0.993 -0.425 -4.289 8.63 0.950 0.957 -0.206 -4.064 13.9 0.911 0.921 -0.011 -3.857 20.8 0.876 0.891 0.151 -3.682 31.1 0.840 0.861 0.323 -3.504 44.6 0.811 0.840 0.460 -3.351 slope = 1.0, log K = 3.838 temp. = 41.1 °C, X = 673.5 nm, An = 1.036, Aoo = 0.723, [CoTNPc] = 8.6 x lO"6 M [4-pic], x 10-5 M A Acorected log [4-pic] 4.21 0.992 0.995 -0.822 -4.376 10.5 0.938 0.946 -0.394 -3.979 16.7 0.896 0.908 -0.160 -3.777 25.1 0.862 0.879 0.003 -3.600 37.4 0.822 0.846 0.189 -3.427 53.4 0.787 0.821 0.341 -3.272 73.0 0.756 0.801 0.479 -3.137 slope = 1.0, log K = 3.603 H.5. Raw data and data analysis for the binding of 4-tert -butylpyridine to CoTNPc. temp. = 15.0 °C, X = 673.5 nm, Ao =1.197, Aoo-= 0.842, [CoTNPc]: = 1.0 x 10-5 M [4-'Bupy], X 1 0 - 5 M A c^orrected log [4-IBupy] 0.698 1.139 1.139 -0.709 -5.165 1.40 1.085 1.086 -0.342 -4.854 2.16 1.050 1.051 -0.156 -4.666 3.76 1.005 1.007 0.061 -4.425 6.60 0.963 0.966 0.270 -4.180 9.55 0.927 0.931 0.475 -4.020 17.9 0.893 0.901 0.700 -3.747 slope = 1.0, log K = 4.479 temp. = 21.0 'C, X = 673.5 nm, An = 0.716, Aoo = 0.497, [CoTNPc] = 6.0 x lO'6 M [4-<Bupy], xl0-5M A c^orrected log K-'Bupy] 0.940 0.684 0.684 -0.783 -5.027 1.90 0.675 0.657 -0.443 -4.721 3.38 0.630 0.630 -0.206. -4.471 5.35 0.601 0.601 0.028 -4.272 7.83 0.575 0.575 0.231 -4.106 11.4 0.557 0.557 0.375 -3.943 16.3 0.540 0.540 0.529 -3.775 slope =1.1, log K = 4.295 H.5. Raw data and data analysis for the binding of A-tert -butylpyridine to CoTNPc (continued). temp. = 31.0 'C, X = 673.5 nm, Ao = 0.938, Aoo = 0.640, [CoTNPc] = 7.8 x 10-6 M [4-<Bupy], xlO- 5M A Acorected log [4-<Bupy] 1.18 0.905 0.906 -0.920 -4.928 2.31 0.858 0.859 -0.443 -4.636 4.14 0.839 0.841 -0.316 -4.383 7.17 0.804 0.807 -0.105 -4.144 12.1 0.765 0.776 0.076 -3.917 19.4 0.731 0.738 0.310 -3.712 31.6 0.698 0.709 0.521 -3.500 49.6 0.672 0.680 0.810 -3.305 slope = 1.0, log K = 4.057 temperature : = 41.0°C, 1 = 673.5, AQ= 1.428, Aoo = 1.013, [CoTNPc] = 1.2 x 10-5 M [4-'Bupy], x K H M A Acorected log [4-03upy] 0.606 1.328 1.332 -0.522 -4.217 1.05 1.278 1.284 -0.275 -3.979 1.74 1.221 1.231 -0.044 -3.759 2.62 1.171 1.186 0.146 -3.582 3.93 1.121 1.143 0.341 -3.406 5.23 1.083 1.110 0.516 -3.281 7.78 1.047 1.086 0.671 -3.109 slope = 1.1, log K = 3.728 II.6. Raw data and data analysis for the binding of piperidine to CoTNPc. temp. = 10.0 'C, X = 673.5 nm, Ap = 0.422, = 0.268, [CoTNPc] = 3.5 x 1Q-6 M [pip], x 10-5 M A Aqnected l o g X ^ d tog [pip] 0.411 0.396 0.396 -0.692 -5.386 1.56 0.355 0.356 -0.125 -4.807 3.75 0.319 0.320 0.293 -4.426 6.54 0.298 0.300 0.581 -4.184 slope = 1.1, log K = 4.714 temp. = 21.4 'C, X = 673.5 nm, Ap = 1.358, A c = 0.958, [CoTNPc] = 1.1 x 1Q-5 M [pip], x 10-5 M A Acorcctcd l o g A ^ X : tog [pip] 0.448 1.313 1.313 -0.897 -5.349 2.44 1.208 1.208 -0.222 -4.613 5.03 1.114 1.120 0.167 -4.298 10.4 1.029 L041 0.582 -3.983 slope =1.1, log K = 4.474 temp. = 45.0 J C, X = 673.5 nm, Ap = 1.768, Aoo = 1.219, [CoTNPc] = 1.5 x IP'5 M . Ap - A [pip], x 10-5 M A Acnreaed l o g A - Aoo tog [pip] 2.62 1.700 1.705 -0.887 -4.582 9.15 1.561 1.576 -0.269 -4.039 20.1 1.431 1.462 0.100 -3.697 31.0 1.358 1.403 0.297 -3.509 slope = 1.1, log K = 3.785 n.7. Raw data and data analysis for the binding of tetrahydrofuran to CoTNPc. temp. = 11.0 'C, X = 673.5 nm, An =1.305, Aoo = 1.146, [CoTNPc] = 1.1 x 10-5 M [THF], xlO- 2M A Acorected log [THF] 0.847 1.277 1.278 -0.689 -2.072 2.11 1.255 1.257 -0.364 -1.675 4.23 1.229 1.233 -0.082 -1.374 7.16 1.199 1.206 0.217 -1.145 11.3 1.180 1.191 0.404 -0.946 18.8 1.156 1.174 0.670 -0.726 slope = 1.0, log K = 1.348 temp. = 21.0 # C, X - 673.5 nm, Ao= 1.286, Aco = : 1.148, [CoTNPc] = 1.1 x 10-5 M [THF], x 10"2M A Acorected log ^ ° " ^ A - Aoo log [THF] 0.832 1.266 1.267 -0.797 -2.080 2.80 1.274 1.249 -0.436 -1.682 4.15 1.226 1.230 -0.166 -1.382 7.05 1.199 1.206 0.140 -1.152 11.1 1.185 1.196 0.273 -0.953 18.5 1.159 1.177 0.575 -0.734 28.5 1.144 1.171 0.699 -0.545 slope = 1.0, log K = 1.259 H.7. Raw data and data analysis for the binding of terxahydrofuran to CoTNPc (continued). temp. = 31.0 *C, X = 673.5 nm, An = 1.267, A«, = 1.145, [CoTNPc] = 1.1 x 10'5 M [THF], xlO- 2 M A •^ corrected log [THF] 0.822 1.252 1.253 -0.887 -2.085 2.05 1.236 1.238 -0.506 -1.688 4.09 1.218 1.222 -0.233 -1.388 6.95 1.197 1.204 0.028 -1.158 11.0 1.181 1.192 0.203 -0.959 18.2 1.156 1.173 0.526 -0.739 28.1 1.137 1.164 0.734 -0.551 slope = 1.1, log K = 1.206 temperature = 41.0 'C, 1 = 673.5, Ao= 1.247, Aoo = 1.136, [CoTNPc] = 1.1 x 10-5 M [THF], X10-2M A Acorected log [THF] 0.807 1.236 1.237 -1.004 -2.093 2.02 1.222 1.224 -0.583 -1.695 4.03 1.208 1.212 -0.337 -1.395 6.84 1.189 1.196 -0.071 -1.165 10.8 1.173 1.183 0.134 -0.966 17.9 1.150 1.167 0.412 -0.747 27.7 1.129 1.155 0.685 -0.558 slope = 1.1, log K = 1.130 Appendix IH. Raw data and data analysis for magnetic susceptibility measurement of CoTNPc. ELLl. Vibrating sample magnetometer: sample weight: 0.06770 g magnetic field: 9225 Gauss M.W.: 916.00 Zdia: -538 x lO* cm3 mol"1 DIODE HEATER -TC 3 TEMPb TEMPcon-C MOMENT3 CORR.e VOLTAGE (K) (x lO"2) off 5.268 4.11 4.31 0.347 x 10-1 0.063 375 70 5.252 5.33 5.48 0.278 x 10"1 0.090 385 60 5.210 8.21 8.17 0.187 x lO"1 0.121 400 60 5.155 11.66 11.47 0.134 x 10-1 0.132 425 80 5.064 17.06 16.80 0.909 x lO"2 0.156 450 80 4.974 22.37 22.15 0.670 x lO"2 0.155 475 100 4.893 27.20 26.93 0.560 x lO-2 0.143 500 120 4.815 31.90 31.48 0.452 x 10-2 0.141 525 120 4.733 36.87 36.41 0.410 x lO'2 0.110 550 120 4.661 41.25 40.75 0.379 x lO"2 0.102 600 120 4.537 48.73 48.30 0.314 x lO"2 0.089 650 120 4.429 54.57 54.19 0.300 x 10-2 0.077 700 120 4.332 60.85 60.85 0.290 x lO-2 0.060 750 120 4.245 65.89 65.89 0.286 x lO'2 0.048 800 120 4.166 70.40 70.40 0.287 x lO"2 0.040 850 120 4.093 74.53 74.53 0.273 x lO"2 0.031 900 120 4.025 78.33 78.33 0.272 x lO"2 0.035 950 120 3.960 81.95 81.95 0.264 x lO"2 0.041 96 DI.1. Vibrating sample magnetometer (continued): MOMENT Xg Xm TEMPcorr Meff (corr)f (10-6)S (lO"6)11 (lO-ty (K) (B.M.)k 0.03533 56.57 51846 52384 0.052384 4.31 1.344 0.02870 45.95 42090 42628 0.042628 5.48 1.367 0.01991 31.88 29202 29740 0.029740 8.17 1.394 0.01472 23.57 21590 22128 0.022128 11.47 1.425 0.01065 17.05 15617 16156 0.016156 16.80 1.474 0.00825 13.21 12100 12638 0.012638 22.15 1.496 0.00703 11.26 10314 10852 0.010852 26.93 1.529 0.00593 9.50 8702 9240 0.009240 31.48 1.525 0.00520 8.33 7630 8168 0.008168 36.41 1.542 0.00481 7.70 7053 7591 0.007591 40.75 1.573 0.00403 6.45 5908 6446 0.006446 48.30 1.578 0.00377 6.04 5533 6071 0.006071 54.19 1.622 0.00350 5.60 5130 5668 0.005668 60.85 1.661 0.00334 5.35 4900 5439 0.005439 65.89 1.693 0.00327 5.24 4800 5338 0.005338 70.40 1.734 0.00304 4.87 4461 4999 0.004999 74.53 1.726 0.00307 4.92 4507 5045 0.005045 78.33 1.778 0.00305 4.88 4470 5008 0.005008 81.95 1.812 a. Thermocouple readings. b. Temperature readings from a. c. Temperatures after correction. d. Magnetization. 97 e. Magnetization correction for the tube magnetization. f. Magnetization after the correction; MOMENT (corr) = MOMENT + CORR. «7 • u* ^ j u - r . . MOMENT g. Weight magneuc susceptibility Xg = 9225 x 0.0677-h. Molar magnetic susceptibility Xm = Xg x (M. W.). i. Molar magnetic susceptibility corrected for the diamagnetic susceptibility of the complex; Xm = Xm - Zdia-IEt.2. Gouy balance: M.W.: 916.00 g tube: #2 sample weight (W): 0.49315 g p: 2.5617 x 10"4 emu/g Idia: -538 x 10"6 cm3moH mv3 AW -AW*"156 TEMP AW 0 0* Xg Xm Ycoir Meff (mg)b (mg) (K) (mg)c (lO-6^ (10"6)e (10-6)e (B.M.)f 0.72 0.77 2.57 292 3.34 1.73 1.59 2.13 2.23 -0.10 1.01 2.56 272 3.57 1.85 1.70 2.24 2.21 -0.78 1.24 2.54 252 3.78 1.96 1.80 2.34 2.17 -1.36 1.47 2.53 236 4.00 2.08 1.90 2.44 2.15 -2.52 2.01 2.48 201 4.49 2.33 2.14 2.67 2.07 -3.27 2.54 2.41 177 4.95 2.57 2.36 2.89 2.02 -3.97 3.19 2.32 151 5.51 2.86 2.62 3.16 1.95 -4.58 3.99 2.19 126 6.18 3.21 2.94 3.48 1.87 -5.21 5.43 1.98 94.0 7.41 3.85 3.53 4.06 1.75 -5.33 5.93 1.92 85.5 7.85 4.08 3.74 4.27 1.71 -5.43 6.47 1.86 77.5 8.33 4.33 3.96 4.50 1.67 -5.44 6.59 1.81 77.0 8.40 4.36 4.00 4.53 1.67 a. Potentials in millivolts. b. Weight in mg as read directly form the balance with field on. c. AW«>rr = AW-AWtobe. AWcorrxp d. Weight magnetic susceptibility Xg = • e. Molar magnetic susceptibility Xm = Xg x (M- W.). f. | l e f f -2 .83 - ^0" . 

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