Date of Award

12-2000

Level of Access

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Advisor

Alice E. Bruce

Second Committee Member

Mitchell R.M. Bruce

Third Committee Member

François G. Amar

Abstract

The oxidative behavior of Auranofin, 2,3,4,6-tetra-O-acetyl-1-thio-β-D-glucopyranosato-S(triethylphosphine)gold(I), was investigated by using cyclic voltammetry (CV) in 0.1 M Bu4NBF4/CH2Cl2 and 0.1 M Bu4NPF6/CH2Cl2 solutions using Pt working and auxiliary electrodes and a Ag/AgCl reference. CV studies at scan rates from 50-2,000mVs-1 and Auranofin concentrations between 1 and 4mM, show two irreversible oxidation processes occurring at +1.1 V and +1.6 V vs. Ag/AgCl. Treatment of Auranofrn with the one electron oxidizing agent [Cp2Fe]PF6 gave a μ-thiolato digold cluster, [(Et3PAu)2(μ-SR)]22+ and the disulfide, bis(tetraacetlythiog1ucose). A mechanism for Auranofin oxidation is proposed on the basis of chemical and electrochemical studies. The p-thiolato species is also obtained by treatment of Auranofin with Et3PAuN03 in CH3CN or addition of methanolic silver nitrate to an equimolar mixture of Auranofin and Et3PAuCl followed by product isolation. The X-ray structure is reported for the Auranofin analogue, [Au4(PMe3)4(thioglucose)2](NO3)2. The structure of the cluster confirms the coordination of two Me3PAu+ to a bridging thiolato moiety and the two-thiolates are on opposite sides and trans to each other. The gold-gold distances are Au1-Au2= 3.106(7), Au1-AuA= 3.17 1 (1l), and Au2-Au2A= 3.144(12)Å. The cyclic voltammetry of Solganol, aurothioglucose, was investigated in 0.5 M NaClO4/H2O solutions using a three-electrode system consisting of a platinum working electrode, a platinum-wire auxiliary electrode, and a silver-silver chloride reference electrode. A broad peak obtained at +1.2 V, which affected by scan rate and pH changes. Multiple CV scans of Solganol showed an enhancement in current due to a possible filming on the electrode surface. Bulk electrolysis of Solganol showed n=2. Chemical oxidation using [Cp2Fe]PF6 showed no change in the NIvR peaks and there was no change in the color of the mixture. Based on bulk electrolysis, resistance to chemical oxidation, and pH studies, the peak at +1.2 V vs. Ag/AgCl was assigned as AuI/III. A series of binuclear Au(I) halide and thiolate complexes (AuX)2dppbz (X = Cl, Br, I, p-SC6H4CH3) were synthesized. All of the newly synthesized complexes gave satisfactory elemental analysis and characterized by 'H and 31P NMR. The complex (AuCl)2dppbz crystallized in the orthorhombic space group Pbca with a = 16.955(3), b = 18.160(2), c = 22.225(1) Ã, a = β = γ =90°, Z = 8 (at 293 K). The Au ... Au bond length of 2.99 8, is in the range of gold-gold interaction distance.

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