Reversible Conversion of Disulfide/Dithiolate Occurring at a Vanadium(IV) Center: A Biomimetic System for Redox Exchange in Vanabin

Abstract

Ascidians use a class of cysteine-rich proteins generally referred to as vanabins to reduce vanadium ions, one of the many biological processes that involve the redox conversion between disulfide and dithiolate mediated by transition-metal ions.To further understand the nature of disulfide/dithiolate exchange facilitated by a vanadium center, we report herein a six-coordinate non-oxido V IV complex containing an unbound disulfide moiety,with TEMPO (TEMPO = 2,2,6,6-tetramethylpiperidin-1-yl)oxyl) via hydrogen atom transfer. Importantly, complex 1 can be reduced by two electrons to form an eight-coordinate V IV complex, [V IV (PS3″) 2 ] 2− (4). The reaction can be reversed through a two-electron oxidation process to regenerate complex 1. The redox pathways both proceed through a common intermediate, [V(PS3″) 2 ] − (3), that has been previously reported as a resonance form of V V -dithiolate and a V IV -(thiolate)(thiyl-radical) species. This work demonstrates an unprecedented example of reversible disulfide/dithiolate interconversion mediated by a V IV center, as well as provides insights into understanding the function of V V reductases in vanabins.

Import and Implications of Vanadium in Live Aspects

“…For a biomimetic system modelling the reduction of vanadate (V) and coordination of non-oxido-V IV to vanabin, see ref. [24].…”