Session: Electrochemistry and Electrocatalysis:

Sulfur-based redox switches are critically important in modulating biological systems. We have been interested in studying sulfur-based switches in model systems where the flow of electron transfer of sulfur-metal complexes can be altered using a secondary redox couple. This interest also extends to the study of sulfur-zinc and sulfur-gold complexes which undergo metal-mediated thiolate-disulfide exchange as well as sulfur-gold complexes which may have anti-arthritis, antimicrobial or anticancer activity. The sluggishness of oxidative electron transfer in gold-sulfur complexes is characterized by irreversible, broad anodic sulfur-based redox waves with peak currents many times lower than predicted for fast electron transfer. Oxidation of the gold(I)-sulfur complexes produces disulfide and multinuclear gold(I)-sulfur cationic clusters. Previous study involving Ph₃PAu(SC₆H₄CH₃) has indicated that ferrocene can enhance sulfur-based electron transfer. In the present study, auranofin analogues of gold(I) complexes with tri(2-furyl) phosphine and substituted pyrimidine-2-thiolates were synthesized, characterized (NMR, IR, elemental analysis, mass spectrometry, X-ray), and investigated by cyclic voltammetry in the presence of ferrocene. Results indicate that adding ferrocene as an electron transfer catalyst lowers the barrier for sulfur-based oxidative electron transfer by 160 to 280 mV.

Alice Bruce

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