Inaug.-diss.--University of Iowa. / "Reprinted from the Physical review, vol. xxxi, no. 4, October, 1910."

Thesis (Ph. D.)--Columbia University, 1932. / Vita. Bibliography: p. 28.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 185-191). Also available via the Internet.

University, Diss., 1999--Osnabrück.

This thesis describes the synthesis and chemistry of triangular phosphido-bridged iridium clusters. The cluster [Ir3(μ-PPh2)3 (CO)6] was obtained analytically pure for the first time. In the solid state this 48 electron cluster exhibits one short iridium-iridium bond of 2.6702(3) Å and two long iridium-iridium bonds, 2.9913(3) Å on average. Two phosphido bridges rest closely within the plane of the metal triangle while the unique phosphido group, bridging the short metal-metal bond, is almost orthogonal to this plane. NMR data suggest that this structure is also adopted in solution below 183 K. At higher temperature however the phosphido bridges give rise to an average signal which is presumably due to a rapid flip-flop motion of these groups. Addition of one molar equivalent of dimethylacetylendicarboxylate to [Ir3(μ-PPh2)3(CO)6] results in formation of [Ir3(μ-PPh2)3(CO) 6(μ-DMAD)] which contains a diiridacyclobutene. Addition of excess alkyne leads to the CO-inserted [Ir3(μ-PPh2) 3(CO)5(μ-DMAD){κ2-MeO 2CCC(CO2Me)C(O)}] which photochemically decarbonylates, to give [Ir3(μ-PPh2)3(CO)5(μ-DMAD) 2]. The 50 electron cluster [Ir3(μ-PPh2) 3(CO)5(t-BuNC)2] also reacts with dimethylacetylendicarboxylate to yield the CO-inserted [Ir3(μ-PPh2)3(CO) 3(t-BuNC)2{κ2-MeO2CCC(CO 2Me)C(O)}2] in two isomeric forms. The new CO-insertion products represent stable iridacyclobutenones which are reluctant to undergo further insertion reactions involving carbon monoxide, tert-butylisocyanide or dimethylacetylenedicarboxylate. Addition of dimethylacetylendicarboxylate to cluster mixtures containing predominantly [Ir2Rh(μ-PPh2)3(CO) 5] and [Ir3(μ-PPh2)3(CO)6] results in selective reaction at the tri-iridium cluster which allowed for the isolation of the heterometallic cluster by chromatography. In contrast to the tri-iridium parent, [Ir2Rh(μ-PPh2)3(CO) 5] is much less reactive to dimethylacetylendicarboxylate and inert to CO. Similarly, the heterometallic [Ir2Rh(μ-PPh2) 3(CO)4(RNC)3] (R = tert-butyl; 1,1,3,3-tetramethylbutyl) are reluctant to undergo oxidative addition reactions with dimethylacetylendicarboxylate and iodomethane which readily afford addition products with the homometallic parent clusters. The kinetic difference is a consequence of electronic rather than steric factors in the clusters. / Graduate

Luminescent transition metal complexes have arisen as viable alternatives to organic dyes for sensory applications due to their notable advantages. This thesis aimed to synthesize different kinds of Ir(III) complexes, explore their interactions with DNAs and investigate their application for the construction of label-free oligonucleotide-based sensing platforms. A series of Ir(III) complexes incorporating a variety of C^N and N^N donor ligands were synthesized and were shown to exhibit G-quadruplex-selective binding properties via emission titration, UV/vis titration, fluorescence resonance energy transfer melting and G-quadruplex fluorescent intercalator displacement experiments. These G-quadruplex-selective Ir(III) complexes were utilized as signal transducers to monitor the conformational changes of oligonucleotides in label-free oligonucleotide-based luminescent detection platforms for metal ion (Sr2+), small molecules (GSH and ATP), protein (human neutrophil elastase) and enzyme activities (polymerase, hepatitis C virus NS3 helicase).

No description available.

No description available.

Poly(vinylbenzylchloride) (PVBC) nanofibers were fabricated by the electrospinning process. The Merrifield micropheres, silica microsparticles and PVBC nanofibers were functionalised with different quaternary diammonium groups derived from ethylenediamine (EDA), tetramethylenediamine (TMDA), hexamethylenediamine (HMDA), 1,8-diaminooctane (OMDA), 1,10-diaminodecane (DMDA) and 1,12-diaminododecane (DDMDA) and investigated for separation of [RhCl5(H2O)]2- and [IrCl6]2-. The sorbent materials were characterised by means of FTIR, XPS, SEM, BET surface area, thermogravimetric analysis and elemental analysis, and characterization results showed that the functionalization of the sorbent materials was successful. Batch equilibrium studies were carried out to assess the efficiency of these different anion exchangers using single metal aqueous solutions. The adsorption isotherms and kinetics of both [RhCl5(H2O)]2- and [IrCl6]2- adsorption onto the sorbent materials are presented. The isothermal batch adsorption studies fitted the Freundlich model indicating heterogeneous surface adsorption. The Freundlich isotherm confirmed multilayer adsorption and the Freundlich constant (kf) displayed the following ascending order for nanofibers (F-QUAT EDA, F-QUAT TMDA, F-QUAT HMDA, F-QUAT OMDA and F-QUAT DMDA), silica microparticles (Si-QUAT EDA, Si-QUAT TMDA, Si-QUAT HMDA, Si-QUAT OMDA and Si-QUAT DMDA) and microspheres (B-QUAT EDA, B-QUAT TMDA, B-QUAT HMDA, B-QUAT OMDA and B-QUAT DMDA) and a decrease in kf for F-QUAT DDMDA, Si-QUAT DDMDA and B-QUAT DDMDA has been observed. The pseudo second-order model was found to be the best fit to describe the adsorption kinetics of both metal ions complexes onto all the sorbent materials. K2 value in pseudo second-order kinetics showed that the rate constant for adsorption of [IrCl6]2- onto nanofibers was larger than for silica microparticles and Merrifield microspheres. Column sorption of [IrCl6]2- and [RhCl5(H2O)]2- was carried out and the loading capacities of [IrCl6]2- were obtained, and they showed dependence on the length of the methylene spacer between the two diammonium centres. [RhCl5(H2O)]2- was not adsorbed by the sorbent materials while [IrCl6]2- was loaded onto the column. The highest iridium loading capacities for all the sorbent materials for the diamines with decylene spacer, and were found to be 32.94 mg/g, 29.35 mg/g, and 27.09 mg/g for F-QUAT DMDA, Si-QUAT DMDA and B-QUAT DMDA respectively. It was also observed on the derivatives of DMDA supported on nanofibers that F-QUAT ethyl loading capacity for iridium (19.89 mg/g) reduced which may be due to the electron-donating nature of the ethyl group and the increase of hydrophobicity whereas F-QUAT benzyl loading capacity (244.64 mg/g) increased dramatically due to increase in the size of the cation which lowers the positive charge density of the quaternary diammonium center. The charge delocalizing ability of the benzyl group resulted in the best interaction of the diammonium group derived from this quaternizing agent, yielding the highest loading capacity for [IrCl6]2-. Reusability was conducted and the results showed that the all the sorbent materials can be used repeatedly without decreasing their adsorption capacity significantly. The neat diammonium salts were also synthesized and interacted with the chorido metal complex anions to form ion-pairs which were then studied for their solubility. The synthesis of the quaternary salts was rather challenging and resulted in some interesting species when impurities of the iodide form of the salts were present in the process of converting them to the iodide form. Some of these include I52+, which was confirmed preliminarily by X-ray structural analysis, potentiometry and cyclic voltammetry. Molecular modeling studies were also conducted to explain the interaction of the chlorido anions with the cationic diammonium centres, and to quantify these interactions by thermodynamic parameters, partial charge calculations, dipole moments and electrostatic potentials, and there was good agreement between theory and experiment. This thesis presents iridium-specific materials that could be applied in solutions of secondary PMGs sources containing rhodium and iridium as well as in feed solutions from ore processing.

A kinetic study was undertaken to investigate the potentiality of rhodium chioro complexes containing diethyl sulphide ligands as homogeneous catalysts. Preliminary studies have also been carried out on the analogous iridium complexes and some rhodium complexes containing arsenic ligands. Under mild conditions of temperature and pressure (70-85°C and upto one atmosphere of hydrogen), it was found that cis RhCl₃(Et₂S)₃ in dimethylacetamide solution is an active catalyst for the homogeneous hydrogenation of maleic acid, trans cinnamic acid and ethylene. In benzene solution, no homogeneous hydrogenation occurred. The kinetics of the maleic acid hydrogenation have been studied in detail and it was found that the hydrogenation process consisted of two rate determining steps: the initial hydrogen reduction of Rh(III) to Rh(I) which complexed rapidly with the maleic acid present and the subsequent hydrogenation of the Rh(I) - maleic acid complex to yield succinic acid and Rh(I) again. The detailed mechanisms of these steps, with particular emphasis on solvent effects are discussed. The corresponding IrCl₃(Et₂S)₃ complex and Rh(III) complexes with "difars" and "diars" (two chelating arsenic ligands) were inactive as homogeneous hydrogenation catalysts, however reactions with H₂ were observed with the iridium complex itself and also the rhodium difars complex; these reactions are also discussed. / Science, Faculty of / Chemistry, Department of / Graduate