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Wong, Fai George. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references. / Abstracts in English and Chinese. / Abstract --- p.iii / 摘要 --- p.v / Acknowledgment --- p.vii / Table of Contents --- p.ix / Abbreviations --- p.xiii / Selected List of Tables --- p.xv / List of Compounds --- p.xvi / Chapter Chapter 1 --- Introduction on Metal Amides / Chapter 1.1 --- General Background --- p.1 / Chapter 1.2 --- A General Classification of A/-anionic Ligands --- p.1 / Chapter 1.3 --- Development of Late Transition Metal Amides --- p.3 / Chapter 1.3.1 --- The First Reported Metal Amides from Each Major Block of the eriodic Table --- p.4 / Chapter 1.3.2 --- Metal Amides Supported by the Simple [N(SiMe3)2]- Ligand --- p.4 / Chapter 1.3.3 --- From Simple to Bulkier Silylamido Ligands --- p.6 / Chapter 1.3.4 --- Metal Complexes Supported by Borylamido Ligands --- p.7 / Chapter 1.3.5 --- Metal Complexes Supported by Arylamido Ligands --- p.9 / Chapter 1.3.6 --- Metal Complexes Supported by erfluorinated Arylamido Ligands --- p.10 / Chapter 1.4 --- Objectives of This Work --- p.11 / Chapter 1.5 --- References for Chapter 1 --- p.13 / Chapter Chapter 2 --- Ligand Substitution Reactions of Divalent Late Transition Metal Amides / Chapter 2.1 --- General Background --- p.17 / Chapter 2.2 --- Objectives of This Work --- p.19 / Chapter 2.3 --- Results and Discussion --- p.20 / Chapter 2.3.1 --- Previous Work in Our Group --- p.20 / Chapter 2.3.2 --- Synthesis of Metal Complexes --- p.20 / Chapter 2.3.3 --- Molecular Structure of the Fe(ll) Complex 11 --- p.22 / Chapter 2.3.4 --- Preparation of Mixed Amide-Alkyl Complexes --- p.24 / Chapter 2.3.5 --- Molecular Structures of the Methyl Complexes 12-15 --- p.29 / Chapter 2.3.6 --- Attempts to repare Mixed Amide-Alkoxide Complexes --- p.39 / Chapter 2.3.7 --- Reactivity of the [Co(L2)Me(tmeda)] Complex (17) --- p.39 / Chapter 2.3.8 --- Molecular Structure of the Co(ll) Iodide Complex 18 --- p.43 / Chapter 2.4 --- Summary --- p.45 / Chapter 2.5 --- Experimental Section for Chapter 2 --- p.48 / Chapter 2.6 --- References for Chapter 2 --- p.51 / Chapter Chapter 3 --- Reduction Chemistry of Divalent Late Transition Metal Amides / Chapter 3.1 --- General Background --- p.54 / Chapter 3.2 --- Objectives of This Work --- p.57 / Chapter 3.3 --- Results and Discussion --- p.57 / Chapter 3.3.1 --- Reduction of the Complexes Mn(ll) and Co(ll) Complexes 7 and 9 --- p.57 / Chapter 3.3.2 --- Attempted Synthesis of the Mononuclear Co(l) Complex --- p.59 / Chapter 3.3.3 --- Molecular Structures of the Complexes 19 and 20 --- p.61 / Chapter 3.3.4 --- Reactivity of the Univalent Co(l) Complex [Co(L2)]2 (20) --- p.65 / Chapter 3.4 --- Summary --- p.67 / Chapter 3.5 --- Experimental Section for Chapter 3 --- p.68 / Chapter 3.6 --- References for Chapter 3 --- p.69 / Chapter Chapter 4 --- A reliminary Study on the Coordination Chemistry of erfluorinated Late Transition Metal Amides / Chapter 4.1 --- General Background --- p.71 / Chapter 4.2 --- Objectives of This Work --- p.73 / Chapter 4.3 --- Results and Discussion --- p.73 / Chapter 4.3.1 --- Synthesis of the Ligand recursor[HN(SiMe3)(C6F5)] (21) --- p.73 / Chapter 4.3.2 --- Synthesis of the Lithium Reagent [Li(L3)tmeda]] (22) --- p.74 / Chapter 4.3.3 --- Synthesis of the Fe(ll) and Co(ll) Complexes of the L3 Ligand --- p.75 / Chapter 4.3.4 --- Molecular Structures of the Chloride Complexes 23 and 24 --- p.77 / Chapter 4.4 --- Summary --- p.82 / Chapter 4.5 --- Experimental Section for Chapter 4 --- p.83 / Chapter 4.6 --- References for Chapter 4 --- p.85 / "Appendix 1 General rocedures, hysical Measurements, and X-Ray Structure Analysis" --- p.87 / Appendix 2 Selected Crystallographic Data --- p.89 / Appendix 3 NMR Spectra of Compounds --- p.94

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. December 2015. / It is well-established that there is electronic communication between the equatorial and axial ligands in the cobalt corrins. It can therefore be anticipated that the electronic structure of the corrin ligand will affect the chemistry of the axial coordination sites of Co(III) in these complexes. To probe this cis-influence the electronic structure of the corrin was perturbed by substituting the H atom at C10 by Br (which is π electron-donating towards the corrin) in aquacobalamin ([H2OCbl]+), and by NO2 (which is strongly electron-withdrawing) and NH2 (which is strongly electron-donating) in aquacyanocobester ([ACCbs]+). The first part of this study was dedicated to aqua-10-bromocobalamin ([H2O-(10-Br)Cbl]+) and the second part to aquacyano-10-nitrocobester ([AC-(10-NO2)Cbs]+) and aquacyano-10-aminocobester ([AC-(10-NH2)Cbs]+). The successful synthesis of [H2O-(10-Br)Cbl]+, was verified by ESI-MS, 1H and 13C NMR, uv-vis spectroscopy and XRD. The stability constants for the substitution of coordinated H2O by a series of anionic (N3 –, NO2 –, SCN–, SO3 2–) and neutral N-donor ligands (imidazole, DMAP) were obtained for [H2OCbl]+, [H2O-(10-Br)Cbl]+ and [H2O-(10-Cl)Cbl]+ under the same conditions. Substitution of the C10 H by Cl or Br favours the coordination of anionic ligands, but discriminates against the binding of neutral N-donor ligands. The anionic ligands bind more strongly to [H2O-(10-Br)Cbl]+ than to [H2OCbl]+ with log K values between 0.05 and 0.62 (average 0.33) larger. Conversely, neutral ligands bind less strongly to [H2O-(10-Br)Cbl]+ than to [H2OCbl]+ with log K values between 0.29 and 0.36 (average 0.33) smaller. DFT (BP83/TZVP) calculations were used to rationalise these observations. When H is changed to Cl or Br, the metal ion becomes less positive. When the β ligand changes from a neutral to an anionic ligand, the partial charge on the C10 substituent becomes more negative. Replacing C10 H by Cl or Br discriminates against a neutral ligand because of the greater electron richness of the metal. If the ligand is an anion, however, the charge donation can be accepted by delocalisation onto the C10 substituent. The reaction kinetics of the substitution of H2O in [H2O-(10-Br)Cbl]+ were determined for the ligands N3 – and imidazole and were compared with values available for [H2OCbl]+ and [H2O-(10- Cl)Cbl]+. The results showed that both N3 – and imidazole react more slowly with [H2O-(10- Br)Cbl]+ than with [H2OCbl]+, consonant with the previous observations for [H2O-(10-Cl)Cbl]+. Although ΔH‡ values are smaller, they do not compensate for significantly more negative values of ΔS‡, indicative of a transition state that occurs earlier along the reaction coordinate in [H2O- (10-Br)Cbl]+ and [H2O-(10-Cl)Cbl]+ whereas the transition state occurs later along the reaction coordinate with [H2OCbl]+. It is argued that this is a consequence of the lower charge density on the metal, making it a better electrophile both towards the incoming and the departing ligand. Dicyano-10-nitrocobester ([DC-(10-NO2)Cbs]) and dicyano-10-aminocobester ([DC-(10- NH2)Cbs]) were synthesised from dicyanocobester [DCCbs] by established methods and converted to the aquacyano form so that the thermodynamics and kinetics of the substitution of coordinated H2O by a variety of ligands could be investigated. The stability constants for the substitution of coordinated H2O by a number of neutral (imidazole, DMAP, methylamine) and anionic (N3 –, NO2 –, SCN–, SO3 2–, CN–) ligands were determined for [ACCbs]+, [AC-(10-NO2)Cbs]+ and [AC-(10-NH2)Cbs]+ in 50% isopropanol. The soft anions (SO3 2– and CN–) bind better to the softer Co(III) metal centre in [AC-(10-NH2)Cbs]+ and [ACCbs]+ than in [AC-(10-NO2)Cbs]+ and the converse is true for the hard anions (N3 –, NO2 – and SCN–). The case is less clear for the N-donor ligands; DMAP clearly has a higher affinity for [AC-(10- NH2)Cbs]+ and [ACCbs]+ than for [AC-(10-NO2)Cbs]+, but there is little discrimination in the case of imidazole and methylamine. This implies that the affinity of the metal for an exogenous ligand depends on the electron density at the metal centre. DFT calculations showed that as the C10 substituent is changed from NH2 to H to NO2, the charge density on the metal centre decreases and the metal becomes harder. The kinetics of the substitution of H2O by CN– in [ACCbs]+, [AC-(10-NO2)Cbs]+ and[AC-(10- NH2)Cbs]+ in 50% isopropanol were determined. The results showed that the substitution of coordinated H2O proceeded with biphasic kinetics and through a dissociative interchange (Id) mechanism where there is nucleophilic participation of the entering ligand in the transition state. The slower phase corresponds to the substitution of coordinated H2O trans to OH– in the aqua hydroxo species, which, together with the dicyano species, is inevitably present in solutions of [ACCbs]+, and the faster phase corresponds to the substitution of the coordinated H2O trans to CN– in the aquacyano species. The difference in rate of the reaction of the [AC-(10-Z)Cbs] (Z = H, NH2 and NO2) was not very large, the ratio between the largest (for Z = H) and the smallest (for Z = NO2) is just over 40, and does not follow the electron donor properties of Z. This is misleading, however, because of a compensation effect between ΔH‡ and ΔS‡. As values of ΔH‡ become smaller, which causes an increase in the reaction rate, ΔS‡ becomes less positive (or more negative), which causes a decrease in the reaction rate. Hence, comparing rate constants at any particular temperature is not very informative and the compensation effect masks the very significant differences in the reactivity of the metal ion towards the entering CN– ligand. The compensation effect is attributed to the position of the transition state along the reaction coordinate, which depends on the charge density on the metal ion. Indeed, if all three reactions had the same value of ΔS‡ then the values of the rate constant would be in the approximate ratio 109:106:1 for Z = NH2, H and NO2, respectively. This study shows that how profoundly the perturbation of the electronic structure of the corrin affects the thermodynamic and kinetic properties of the Co(III) ion, and provides further evidence that the unusual chemistry of Co(III) in the cobalt corrins is a consequence of the cis-influence of the equatorial macrocyclic ligand. / LG2017

This thesis describes the synthesis and X-ray crystallographic analysis of a series of supramolecular architectures prepared using seven flexible multimodal ligands with Ag(I), Cu(I), Cd(II), Co(II), Ni(II) and Pd(II) metal salts. Chapter one introduces some examples of fundamental supramolecular systems with particular focus on metallo-supramolecular motifs, specifically coordination polymers. Topological analysis is discussed as a method for the simplified description and comparison of network structures. Chapter two describes the design, synthesis and characterisation of the symmetrical ligands bis(2-pyrazylmethyl)sulfide (psp), bis(4-pyrimidylmethyl)sulfide (msm) and 5,5�-(thiodimethylene)di-pyrazine-2-carboxylic acid methyl ester (csc) as well as the asymmetrical ligands 2-benzylsulfanylmethyl-pyrazine (psb), 2-pyridylsulfanylmethyl-pyrazine (psd), 3-pyridylsulfanylmethyl-pyrazine (psn) and 4-pyridylsulfanylmethyl-pyrazine (psy). Chapter three presents a literature review of ligands related to psp, msm and csc, followed by the synthesis and characterization of thirteen Ag(I), Cd(II), Co(II), Ni(II) and Pd(II) complexes. The X-ray crystal structures of nine of these complexes are reported and compared. The structures were present as either one- or two-dimensional coordination polymers. The {[Ag(psp)](PF₆)}[infinity] and {[Ag₂(psp)(C₆H₆)(CH₃CN)₂](PF₆)₂�CH₃CN}[infinity] structures demonstrated a solvent dependence by forming a 1-D twisted ladder with a [eta]�-bound benzene and a 2-D undulating sheet with a 4.8� topology respectively. Six of the structures {[Cd₂(psp)(CH₃CN)(H₂O)(NO₃)₄]�H₂O}[infinity], {[Co(psp)(CH₃CN)₂](ClO₄)₂}[infinity], {[Ni(psp)(NO₃)₂]}[infinity] and {[Ag(msm)](X)}[infinity] (X = BF₄⁻, ClO₄⁻, PF₆⁻) displayed anion-[pi] interactions between multi-atomic anions and [pi]-acidic ring centres. A novel N[pz]���cent[pz] T-shaped [pi]-[pi] interaction was also identified in the {[Ni(psp)(NO₃)₂]}[infinity] structure. A 2-D sheet with 6� topology was observed in the X-ray structure of {[Ag₂(csc)](NO₃)₂}[infinity]. Following a review of related ligands, chapter four focuses on seven Ag(I), Cd(II), Co(II) and Cu(I) complexes formed using the asymmetric pyrazine-benzene ligand psb. In total six 1-D coordination polymer chains are reported. Two structurally disparate supramolecular isomers were formed in [Ag(psb)NO₃][infinity] and {[Ag₂(psb)₂NO₃]NO₃�H₂O}[infinity]. The compound {[Ag(psb)](BF₄)}[infinity] was similar to the former isomer [Ag(psb)NO₃][infinity]. The structurally similar coordination polymers {[Cd(psb)(H₂O)(NO₃)₂]}[infinity] and {[Co(psb)(H₂O)₃](ClO₄)₂�H₂O}[infinity] formed structures that showed anion-[pi] interactions using coordinated and non-coordinated anions respectively. The [Cu₂(psb)I₂][infinity] chain consisted of ligands linked together by a Cu₄I₄ stepped cubane tetramer. Chapter five presents seventeen Ag(I) and Cu(I) complexes prepared using three asymmetric pyrazine-pyridine ligands psd, psn and psy. A review of asymmetric pyrazine-pyridine ligands is provided. Seventeen X-ray crystal structures are described. Four psd complexes using AgBF₄, AgClO₄, AgNO₃ and AgPF₆ crystallised as discrete dimers with three types of crystal packing and ligand-supported Ag���Ag interactions. The complexes {[Ag₂(psd)₂CF₃SO₃]CF₃SO₃}[infinity] and {Cu₂(psd)I₂}[infinity] were a 1-D X-shaped chain and a 2-D 6� net respectively. The isostructural 2-D sheets in {[Ag(psn)]ClO₄}[infinity] and {[Ag(psn)]PF₆�CH₃CN}[infinity], had 4.8� topologies whereas a thicker sheet was formed in {[Ag₂(psn)₂](BF₄)₂}[infinity] with a complicated (4�.6�.8�)₂(4.6.8)₂ topology. The {[Ag₃(psn)₂](CF₃SO₃)₃�CH₃CN}[infinity] chain polymer displayed three different coordination geometries around the three Ag(I) centres with two ligand-unsupported Ag���Ag interactions. The complex [Cu₂(psn)₂I₂] crystallised as a discrete dimer with a different ligand arrangement than those found in the psd dimers. Six Ag(I) 3-D networks were formed using psy. The complexes {[Ag(psy)]X}[infinity] (X = BF₄, ClO₄, PF₆) formed as isostructural non-interpenetrated (10,3)-d networks. An unprecedented tri-nodal (4.6.8)₂(6.8�)₂(4.6.8�.10)₂ topology was observed in the {[Ag₂(psy)₂](CF₃SO₃)₂}[infinity] structure. The suprarmolecular isomers {[Ag₃(psy)₂(NO₃)₂]NO₃]}[infinity] and {[Ag₃(psy)₂(NO₃)₃]�H₂O}[infinity] formed inclined interpenetrated 6� sheets and a (4�.6)₂(4⁴.6�.8⁸.10) 3-D network respectively. The structures in this chapter showed a general trend of increasing dimensionality when progressing from psd to psn to psy. Chapter six presents a summary of the more significant results and concluding remarks.

The new Co(III) carbonate complexes [Co(uns-penp)(O₂CO)]ClO₄�H₂O and [Co(trpyn)(O₂CO)]ClO₄, containing tripodal tetraamine ligands, have been synthesised and characterised by microanalysis, �H, ��C and ⁵⁹Co NMR, mass spectrometry (MS) and UV-vis spectroscopy. In addition, the ⁵⁹Co NMR spectra have been obtained for two series of [Co(N₄)(O₂CO)]⁺ complexes containing aliphatic (N₄ = tren, baep, abap, trpn) and pyridyl (N₄ = tpa, pmea, pmap, tepa) tripodal tetraamine ligands and the complex [Co(dppa)(O₂CO)]⁺. The ⁵⁹Co NMR signal increases as [Delta] decreases, indicating there is less electron density at the Co(III) nucleus as the metal-ligand orbital overlap becomes poorer. A linear relationship was found to exist between the [Delta] for the individual complexes and their ⁵⁹Co NMR chemical shifts which follows the relationship: [Delta] = 29 174 + -0.89363 x [delta](⁵⁹Co) For the two series of [Co(N₄)(O₂CO)]+ complexes, plots of the magnetogyric ratio (γ) and [lambda][max] have y-intercepts that do not accurately correspond to the magnetogyric ratio of the bare cobalt nucleus (γ₀(Co)). This is due to the deviation of the complexes from pure octahedral symmetry. A fluxional process in the complex [Co(pmea)(O₂CO)]⁺ was investigated using variable temperate (VT) NMR. This was found to involve the inversion of a six-membered chelate ring about a pseudo mirror plane with a [Delta]G[double dagger] of 58 kJ mol⁻� at 25 �C. Mass spectra have been obtained for all the [Co(N₄)(O₂CO)]⁺ complexes, and these show a common fragmentation pattern for all the complexes except [Co(trpn)(O₂CO)]⁺, where CO₂ is lost from the molecular ion to give a [Co(N₄)O]⁺ adduct. Single crystal X-ray structural analyses were performed on [Co(abap)(O₂CO)]ClO₄ (orthorhombic, Pca2₁, a = 15.9744(11) Å, b = 8.6200(6) Å, c = 21.8568(15) Å, α = β = γ = 90�, Z = 8, R1 = 0.0350, wR2 = 0.0902), [Co(trpn)(O₂CO)]ClO₄�H₂O (monoclinic, P2₁/c, a = 11.9510(19) Å, b = 12.0740(19) Å, c = 12.917(2) Å, β = 117.56(4)�, α = γ = 90�, Z = 4, R1 = 0.0476, wR2 = 0.1188), [Co(tpa)(O₂CO)]ClO₄�2H₂O (triclinic, P-1, a = 16.2298(5) Å, b = 17.2291(5) Å, c = 17.3393(5) Å, α = 106.760(1)�, β = 92.809(1)�, γ = 108.004(1)�, Z = 8, R1 = 0.0349, wR2 = 0.0799), [Co(uns-penp)(O₂CO)]ClO₄�H₂O (triclinic, P-1, a = 6.7544(3) Å, b = 11.5523(5) Å, c = 12.3201(6) Å, α = 73.397(2)�, β = 89.749(2)�, γ = 84.551(2), Z = 2, R1 = 0.0277, wR2 = 0.0842) and [Co(trpyn)(O₂CO)]ClO₄ (monoclinic, P2₁/n, a = 12.2777(5) Å, b = 11.9322(4) Å, c = 27.9622(11) Å, β = 100.082(2)�, α = γ = 90�, Z = 8, R1 = 0.0435, wR2 = 0.1130). Rates of acid hydrolysis of [Co(N₄)(O₂CO)]⁺ (N₄ = baep, abap, trpn, tpa, pmea, pmap, tepa, uns-penp, dppa, trpyn, Me₃-tpa) complexes were measured by stopped flow or UV-vis spectroscopy (I = 1.0 mol L⁻�). The product of acid hydrolysis of [Co(pmea)(O₂CO)]⁺ has been indentified by X-ray crystallography as [Co(pmea)(OH₂)₂]�⁺ (triclinic, P-1, a = 9.7065(5) Å, b = 15.5645(8) Å, c = 11.5740(5) Å, α = 84.660(1)�, β = 123.255(1)�, γ = 104.283(1)�, Z = 2, R1 = 0.0402, wR2 = 0.1009). The acid hydrolysis reactions of the [Co(N₄)(O₂CO)]⁺ complexes containing aliphatic (N₄ = baep, abap, trpn) tripodal tetraamine ligands and [Co(tpa)(O₂CO)]⁺ and [Co(Me₃-tpa)(O₂CO)]⁺ have been investigated over the range [H₃O⁺] = 0.10 - 1.0 mol L⁻� Three processes were observed for the hydrolysis of [Co(baep)(O₂CO)]⁺, [Co(abap)(O₂CO)]⁺ and [Co(trpn)(O₂CO)]⁺ at all [H₃O⁺]. The first and second processes were thought to be [H₃O⁺] dependent, while the third was fit to a first order exponential decay and was [H₃O⁺] independent (k[obs] ~ 4.2 x 10⁻� s⁻� for [Co(baep)(O₂CO)]⁺, 3.8 x 10⁻� s⁻� for [Co(abap)(O₂CO)]⁺ and 3.5 x 10⁻� s⁻� for [Co(trpn)(O₂CO)]⁺). However, none of the processes could be confidently assigned to a step in the acid hydrolysis mechanism. The data obtained from the studies of [Co(tpa)(O₂CO)]⁺ and [Co(Me₃-tpa)(O₂CO)]⁺ showed a single first order [H₃O⁺] dependent process which was fit to the following expression: k[obs] = (k₁K[H₃O]⁺)/(1 + K[H₃O]⁺ This gave k₁ = 5.8 x 10⁻⁴ � 2.3 x 10⁻⁴ s⁻� and K = 0.13 � 0.06 L mol⁻� for [Co(tpa)(O₂CO)]⁺ at 25 �C and k₁ = 6.0 x 10⁻⁵ � 2.0 x 10⁻⁶ s⁻� and K = 0.38 � 0.02 L mol⁻� for [Co(Me₃-tpa)(O₂CO)]⁺ at 50 �C. Both values of K indicate that protonation of chelated carbonate is far from complete at [H₃O⁺] = 1.0 mol L⁻�. Comparative rates of acid hydrolysis at [H₃O⁺] = 6.0 mol L⁻� were obtained for the complexes [Co(tpa)(O₂CO)]⁺ (k[obs] = 1.79 x 10⁻� s⁻�, 25 �C), [Co(pmea)(O₂CO)]⁺ (k[obs] = 1.8 x 10⁻⁵ s⁻�, 25 �C), [Co(pmap)(O₂CO)]⁺ (k[obs] = 2.5 x 10⁻⁵ s⁻�, 50 �C), [Co(tepa)(O₂CO)]⁺ (k[obs] = 4.3 x 10⁻⁵ s⁻�, 25 �C) and [Co(trpyn)(O₂CO)]⁺ (k[obs] = 1.3 x 10⁻⁴ s⁻�, 50 �C) and at [H₃O⁺] = 1.0 mol L⁻� for the complexes [Co(uns-penp)(O₂CO)]⁺ (k[obs] = 2.9 x 10⁻� s⁻�, 25 �C) and [Co(dppa)(O₂CO)]⁺ (k[obs] = 2.7 x 10⁻⁴ s⁻�, 25 �C). The vast differences in the rates of acid hydrolysis can be rationalised on a steric basis. Bulkier ancillary ligands impede the direct protonation of an endo oxygen atom, or the transfer of a proton from the exo to an endo oxygen atom. The chelated bicarbonate complex [Co(trpyn)(O₂COH)]ZnCl₄�3H₂O has been synthesised and characterised by microanalysis and X-ray crystallography (orthorhombic, Pbca, a = 18.1820(66) Å, b = 14.7256(44) Å, c = 19.6344(68) Å, α = β = γ = 90�, Z = 8, R1 = 0.0435, wR2 = 0.1130). The first products of direct metallion of coordinated carbonate, under both acidic and neutral conditions, have been isolated and characterised by microanalysis and IR spectroscopy. The X-ray crystal structures of the bimetallic complexes [Co(Me-tpa)O₂COZnCl₃]�H₂O (triclinic, P-1, a = 8.262(1) Å, b = 11.290(1) Å, c = 13.766(2) Å, α = 95.314(4)�, β = 103.160(4)�, γ = 107.071(5)�, Z = 2, R1 = 0.0382, wR2 = 0.0940) and [Co(pmea)O₂COZnCl₃]�H₂O (triclinic, P-1, a = 8.2916(7) Å, b = 11.0999(11) Å, c = 14.0994(13) Å, α = 8.2916(7)�, β = 102.607(4)�, γ = 108.600(4)�, Z = 2, R1 = 0.0347, wR2 = 0.0770), and the trimetallic complex [(Co(trpyn)(O₂CO))₂Zn(H₂O)̀₄](ZnCl₄)₂�3H₂O (monoclinic, P2₁/c, a = 20.9734(17) Å, b = 17.3712(12) Å, c = 15.7635(13) Å, β = 111.376(4)�, α = γ = 90�, Z = 4, R1 = 0.0235, wR2 = 0.0517) have been obtained. In addition, the X-ray crystal structures of the complexes [Co(trpyn)(O₂CO)](Zn(OH)₂Cl₃)�4H₂O (triclinic, P-1, a = 7.4962(7) Å, b = 13.4019(11) Å, c = 13.6887(11) Å, α = 74.631(4)�, β = 82.893(4)�, γ = 82.324(4)�, Z = 2, R1 = 0.0268, wR2 = 0.0638) and [Co(tepa)(O₂CO)]₂(ZnCl₄)�3H₂O (triclinic, P-1, a = 9.9250(10) Å, b = 15.5561(13) Å, c = 15.8730(16) Å, α = 89.545(4)�, β = 85.019(5)�, γ = 72.714(4)�, Z = 2, R1 = 0.0291, wR2 = 0.0722) were obtained. These two complexes were synthesised under analogous conditions to the bi- and trimetallic complexes. However, in these cases metallation of chelated carbonate did not occur. DFT calculations have been used to calculate the relative energies of pairs of geometric isomers of [Co(N₄)(O₂CO)]⁺ complexes (N₄ = baep, abap, pmea, pmap, dppa, Me-tpa, Me₂-tpa). In all cases, except that of [Co(Me-tpa)(O₂CO)]⁺, the calculations correctly predict that the experimentally observed isomer is lower in energy. An electronic study on two series of [Co(N₄)(O₂CO)]⁺ complexes containing pyridyl (N₄ = tpa, pmea, pmap, tepa) and Me-pyridyl (N₄ = tpa, Me-tpa, Me₂-tpa, Me₃-tpa) tripodal tetraamine ligands correctly reproduces the observed trends in ⁵⁹Co NMR chemical shift and [Delta] values. A molecular orbital analysis of the two series of complexes shows that there is no significant difference between the highest energy occupied orbitals with the largest contribution from the coordinated oxygen atoms. Bond decomposition analyses of the two series of complexes indicate that there is also no difference in total bond energies. These results indicate that there is no electronic explanation for the large differences in reactivity towards acid that is observed experimentally. The first mononuclear complex containing chelated hydrogen phosphate, [Co(pmea)(O₂PO₂H)]ClO₄, has been synthesised and characterised using microanalysis, �H, ��C, ��P and ⁵⁹Co NMR, UV-vis spectroscopy and X-ray crystallography (monoclinic, P2₁/c, a = 8.7017(17) Å, b = 27.639(5) Å, c = 9.586(2) Å, β = 112.818(9)�, α = γ = 90�, Z = 4, R1 = 0.0443, wR2 = 0.1076). The X-ray crystal structure of [Co(pmeaH)(OH₂)Cl₂](CoCl₄)�H₂O (orthorhombic, P2₁2₁2₁, a = 12.6354(3) Å, b = 12.6354(3) Å, c = 15.8261(11) Å, α = β = γ = 90�, Z = 4, R1 = 0.0397, wR2 = 0.0954), in which the pmea ligand is coordinated in a hypodentate fashion, was also obtained. [Co(pmeaH)(OH₂)Cl₂](CoCl₄)�H₂O is thought to be an impurity in crude samples of [Co(pmea)Cl₂]Cl. The pK[a] of [Co(pmea)(O₂PO₂H)]⁺ was determined to be 4.99 � 0.02 by potentiometric titration. A ring inversion fluxional process, analogous to that observed for [Co(pmea)(O₂CO)]⁺, was found by VT-NMR to have a [Delta]G[double dagger] of 60 kJ mol⁻� at 35 �C. A ��P NMR spectrum, taken after the solution was left standing for approximately three hours, showed evidence of cleavage of the hydrogen phosphate chelate via a bimetallic hydrolysis mechanism. Attempts were also made to synthesise Co(III) complexes containing chelated phosphate ester ligands (monomethyl phosphate and monophenyl phosphate), with pmea as the ancillary ligand. ��P NMR spectra of the crude samples indicate that the monomethyl phosphate moiety is chelated to Co(III) (��P [delta] = 21.05 ppm). However, it is unclear whether the monophenyl phosphate is chelated or bridging between two Co(III) ions (��P [delta] = 14.36 ppm).

Thesis (Ph.D.)--McMaster University, 2005. / Supervisor: John F. Valliant. Includes bibliographical references.

Bibliography: leaves 143-153. Studies the complexation of metal ions with the macrocyclic ligand, 1, 4, 8, 11-tetrakis (2-hydroxyethyl)-1, 4, 8, 11-tetraazacyclotetradecane (THEC)

Peroxisome proliferator-activated receptors (PPARs) are members of a large group of ligand-regulated transcription factors that includes nuclear receptors for steroid and thyroid hormones, retinoids and vitamin D���. Synthetic fibrates and thiazolidinediones that bind to and activate PPARs are used efficaciously in humans to remedy hypertriglyceridemia and non-insulin dependent diabetes mellitus, respectively. The objective of the studies described herein was to elucidate the molecular mechanisms of ligand-dependent PPAR signaling. Several PPAR ligands, including WY-14,643, were demonstrated to directly induce PPAR�� conformational changes as evidenced by a differential protease sensitivity assay. Conformational changes were induced in a dose-dependent manner which paralleled that of ligand to induce transcriptional activation. Direct interaction of ligands with, and the resulting conformational alterations in, PPAR�� may facilitate interaction of the receptor with transcriptional intermediary factors and thus may underlie the molecular basis of ligand-dependent transcriptional activation mediated by PPAR��. The yeast two hybrid screen was utilized to identify downstream components of the PPAR�� signaling pathway. Using this technique, the coactivator proteins, p300 and steroid receptor coactivator-1 (SRC-1), were identified as PPAR��-interacting proteins and WY-14,643 potentiated these interactions. p300 also enhanced the transcriptional activation properties of PPAR�� and, therefore, can be considered a bona fide coactivator for this nuclear receptor. Nuclear receptor corepressor (NCoR) was also isolated as a PPAR��-interacting protein from a yeast two hybrid screen. In contrast to the ligand enhanced PPAR��-coactivator interactions, WY-14,643 inhibited NCoR interaction with PPAR��. NCoR and the coactivators, p300 and SRC-1, were also demonstrated to require distinct receptor regions for efficient interaction with PPAR��. Results described herein demonstrate that ligand induces PPAR�� conformational changes, promotes PPAR��-coactivator (p300 and SRC-1) interactions, and inhibits PPAR��-NCoR interactions. We hypothesize that such molecular events are critical for ligand-dependent transcriptional activation by PPAR��. These results contribute additional knowledge as to the molecular mechanisms of PPAR-dependent signaling and may act as a starting part for the improvement and/or development of therapeutic strategies aimed at manipulating this signaling pathway. / Graduation date: 1999

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.