Cross-Talks Between Sulfane Sulfur and Thiol at a Zinc(II) Site

Transformations of sulfane sulfur compounds (e. g. organic polysulfides (R?S_n?R, n>2) and elemental sulfur (S₈)) play pivotal roles in the biochemical landscape of sulfur, and thus supports signaling activities of H₂S. Although a number of previous reports illustrate amine mediated reactions of S₈ and thiol (RSH) yielding R?S_n?R, this report illustrates that a tripodal Zn^II] complex ( Bn₃Tren )Zn^II?OH₂](ClO₄)₂ ( 1 ) facilitates the reactions of sulfane sulfur and thiol (RSH), thereby offering an amine-free biologically relevant complementary route. UV-vis monitoring of the reactions and a set of control experiments underline the definitive role of Zn^II] coordination motif in the reactions of sulfane sulfur (e. g. S₈ and R?S_n?R) with RSH. Detailed investigations (UV-vis, NMR, ESI-MS, intermediate trapping, and TEMPO radical interference experiments) disclose the key differences in the Zn^II] versus previously known amine mediated routes. Moreover, the persulfide (RSS^?) trapping experiments using 1-fluoro-2,4-dinitrobenzene (F-DNB) reveal the intermediacy of RSS^? species in the Zn^II] mediated reactions of sulfane sulfur and thiol, thereby demonstrating Zn^II] assisted persulfidation of thiol in the presence of sulfane sulfur species. Of broader impact, this study underscores the feasible influence of biologically relevant Zn^II] coordination motifs (e. g. carbonic anhydrase) on the sulfane sulfur chemistry in biology.