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 H₂ S. 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 [(Bn₃ Tren)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.