Chemically Reversible Reactions of Hydrogen Sulfide with Metal Phthalocyanines

[Image: see text] Hydrogen sulfide (H(2)S) is an important signaling molecule that exerts action on various bioinorganic targets. Despite this importance, few studies have investigated the differential reactivity of the physiologically relevant H(2)S and HS(–) protonation states with metal complexes. Here we report the distinct reactivity of H(2)S and HS(–) with zinc(II) and cobalt(II) phthalocyanine (Pc) complexes and highlight the chemical reversibility and cyclability of each metal. ZnPc reacts with HS(–), but not H(2)S, to generate [ZnPc-SH](−), which can be converted back to ZnPc by protonation. CoPc reacts with HS(–), but not H(2)S, to form [Co(I)Pc](−), which can be reoxidized to CoPc by air. Taken together, these results demonstrate the chemically reversible reaction of HS(–) with metal phthalocyanine complexes and highlight the importance of H(2)S protonation state in understanding the reactivity profile of H(2)S with biologically relevant metal scaffolds.