Bibliography: leaves 177-193 / v, 193 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Organic Chemistry, 1985

ABSTRACT AXIAL LIGAND SUBSTITUTION REACTION KINETICS OF PYRIMIDINE-2-THIONATO BRIDGED BINUCLEAR PLATINUM(III) COMPLEXES G&ouml / y, Aytun&ccedil / M. S. Department of Chemistry Supervisor: Prof. Dr. H&uuml / seyin iS&ccedil / i Co-supervisor: Assoc. Prof.Dr. Seniz &Ouml / zalp Yaman September 2007, 89 pages The kinetics of the ligand substitution reactions, which is represented by the equation, [Pt2(C4H3N2S)4X2] + 2Y- Pt2(C4H3N2S)4Y2 + 2X- where X- = Cl-, Br-, I- and Y- = Cl-, Br-, I- are studied in acetonitrile in the presence of excess Y- ion concentrations, under constant ionic strength. All reactions are reversible. The rate of the above reaction is dependent on binuclear complex and entering ligand concentrations. Thus general rate equation can be written as Rate = k [Y-]a[Pt2(C4H3N2S)4X2]b The reaction rates are first order with respect to the substrate complex (b=1). The experimentally determined values of the order of the reaction with repect to entering ligand, &ldquo / a&rdquo / , are 0.96&plusmn / 0.057 (X=I-, Y=Cl-), -0.49&plusmn / 0.037 (X=Cl-, Y=I-), 0.28&plusmn / 0.023 (X=I-, Y=Br-), 0.48&plusmn / 0.044 (X=Br-, Y=I-), 0.53&plusmn / 0.042 (X=Br-, Y=Cl-), and -0.21&plusmn / 0.014 (X=Cl-, Y=Br-). The rate constants are 12.1&plusmn / 2.05 M-1s-1 (X=I-, Y=Cl-), (5.7&plusmn / 1.6)x10-3 M1/2s-1 (X=Cl-, Y=I-), 0.3&plusmn / 0.27 M-0.3s-1 (X=I-, Y=Br-), 0.53&plusmn / 0.11 M-1/2s-1 (X=Br-, Y=I-), 1.74&plusmn / 0.16 M-1/2s-1 (X=Br-, Y=Cl-), and 1.71&plusmn / 0.37x10-2 M0.2s-1 (X=Cl-, Y=Br-). To obtain information about the energetics of the reactions, the temperature dependence of the rate constants is determined and the activation parameters &amp / #916 / H* and &amp / #916 / S* are calculated. The values &amp / #916 / S* are negative and, in the range of -81 and -236 J K-1 mol-1. These results support an associative-interchange, Ia, mechanism. All data obtained in this work are used to propose a mechanism which will be consistent with the experimentally determined rate law.

Thesis (M. S.)--Materials Science and Engineering, Georgia Institute of Technology, 2005. / Committee Chair: Kenneth Sandhage; Committee Members: Joe Cochran, Robert Snyder and Tom Sanders. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis--Ph. D., University of Hong Kong, 1982. / Cover title.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

Thermodynamic and kinetic analysis of the ligand substitution reactions of different heterometallic Ru(II)-Pt(II) complexes with a series of bio-relevant thiourea nucleophiles of different steric demands and ionic nucleophiles have been investigated as a function of concentration and temperature using UV/visible and stopped-flow spectrophotometric techniques. To achieve this, five different sets of complexes involving mono di and multinuclear homo and heterometallic complexes with tridentate N-donor ligands of different linker ligands were synthesized and characterized by various spectroscopic methods. The substitution reactions of the chloride complexes were studied in methanol in the presence of 0.02 M LiCf3SO3 adjusted with LiCl to prevent possible solvolysis. The aqua complexes were studied in acidic aqueous medium at pH 2.0. All reactions were investigated under pseudo first-order conditions. Density functional theory (DFT) calculations were used to aid further interpretations and understandings of the experimental results. Substitution reactivity of heterometallic Ru(II)-Pt(II) and Co(II)-Pt(II) complexes bridged by tetra-2-pyridyl-1,4-pyrazine (tppz) ligand was investigated for the first time. The reactions proceeded via two steps. The pseudo first-order rate constants, kobs(1st and 2nd) for the substitution of the chloride ligand(s) from the Pt(II) complexes and subsequent displacement of the linker. The dechelation step was confirmed by 1H NMR and 195Pt NMR studies. Incorporation of Ru(tppz) moiety increases the substitution reactivity and is ascribed to the increased π-back donation from the tppz ligand which increases the electrophilicity of the metal centre, overall charge and the global electrophilicity index of the complex. However, when changed the second metal centre from a Ru(II) to a Co(II), the rate of substitution decreased by a factor of four due to the weaker π- backbonding from Co(II). The substitution reactivity of another set of heterometallic Ru(II)-Pt(II) complexes with a semi-rigid linker, 4’-pyridyl-2,2’:6’,2”-terpyridine (qpy) showed that replacing the cis pyridyl group by a (tpy)Ru(qpy) moiety lowers the energy of anti-bonding LUMO (π*) orbitals and increases the metal-metal interactions and electronic transition within the complex whereby enhancing the reactivity of Pt(II) centre. However, when two Pt(II) moieties are linked to a (qpy)Ru(qpy), the orthogonal geometry at the Ru(II) metal centre prevents the extended π-electron density to flow through the three metal centres. The kinetic results obtained were supported by pKa and 195Pt NMR studies. Substitution reactions of the mononuclear Pt(II) complexes revealed that the polyethylene glycoxy pendent units act as a σ-donors including the lone pair electrons on the first oxygen atom thereby decreasing the reactivity of the parent Pt(II) terpyridine complex. However, this σ-donation towards the terpyridine moiety was found to be effective only up to one unit of the ethylene glycoxy pendant, beyond which the reactivity was sterically controlled. The dinuclear Pt(II) complexes bridged by polyehtyleneglycol ether units show that the reactivity of the complexes depend on the Pt···Pt distance and the steric hindrance at the Pt(II) centre. The substitution reactivity of heterometallic Ru(II)-Pt(II) complexes bridged by the same polyehtyleneglycol ether units indicate that the presence of Ru(tpy)2 moiety influences the structural geometry of the complex system which in turn controls the reactivity of the Pt(II) centre. This is further driven by the entrapment effect of the nucleophile due to the V-shape geometry adopted by the heterometallic complexes. In all cases the reactivity was also controlled by steric and electronic effects. However, when two metal centres are bridged by a flexible non-aromatic linker, the electronic transitions and the metal-metal interactions were found to be minor, especially for the longer linkers. The 1H and 195Pt NMR spectroscopic techniques were used to further understand the observed substitution kinetics and to confirm the degradation of the bridging ligand from the metal centre(s). In all cases, the negative activation entropies obtained support the associative mode of substitution This investigation reveals that the length and the nature of the bridging linker plays an important role in controlling the reactivity of the heterometallic complexes. It is envisaged that the findings of this project would offer a significant contribution to the pharmacological design of effective anticancer drugs. / Ph.D. University of KwaZulu-Natal, Pietermaritzburg 2013.

he extent of BiInO₃ substitution in the perovskite system xBiInO(₃)-(1 - x)PbTiO₃ and the corresponding raise in the transition temperature were investigated using thermal analysis, dielectric measurements, x-ray diffraction, and electron microscopy. Maximum tetragonal perovskite distortion (c/a = 1.082) was obtained for x = 0.20, with a corresponding Curie temperature of 582°C. Phase-pure tetragonal perovskite was obtained for x less than or equal to 0.25. Compound formation after calcining mixed oxide powders resulted in agglomerated cube-shaped tetragonal perovskite particles, which could be fired to 94.7% of theoretical density (TD). Niobium-modified BIPT ceramics with PT contents of 80% and 85% were found to possess significantly lower dielectric loss at elevated temperatures, making it possible to polarize the materials. Piezoelectric properties were measured for a 1.5 mol% Nb -0.15BI-0.85PT composition with a transition temperature of 542°C; the longitudinal piezoelectric coefficient and coercive field were found to be 60 pC/N and 125 kV/cm, respectively. Compositions of xBiLaO₃-(1 − x)PbTiO₃ over the range 0 < x < 0.225 were calcined and sintered. Dielectric constant with temperature and differential scanning calorimetry measurements were in excellent agreement with respect to a Curie-like tetragonal to cubic transformations starting at 495°C for pure PbTiO₃, shifting to lower temperatures with increasing x. For compositions of x > 0.05, a second higher-temperature (∼600°C) endotherm, and matching dielectric anomaly, were consistently observed, for which there were no structural changes indicated by hot-stage x-ray diffraction. This transformation was interpreted to be similar to a Curie transformation in relaxor ferroelectrics in which localized segregation of B-site cations (below the resolution limit of x-ray diffraction) facilitated ferroelectric behavior.

Thesis (Ph. D.)--University of Adelaide, Dept. of Organic Chemistry, 1985. / Includes bibliographical references (leaves 177-193).

Thesis (Ph.D.)--Baylor University, 2007. / Includes bibliographical references (p. 199-203)

Thesis (doctoral)--Rijksuniversiteit te Utrecht, 1983. / Summary in English. Spine title: Allenylmetaal-reagentia en hun omzetting in allenen, allynen en enige heterocycli. Additional references inserted. Description based on print version record. Includes vita and bibliographies.