Chemically Reversible Reactions of Hydrogen Sulfide with Metal Phthalocyanines

Hydrogen sulfide (H2S) is an important signaling molecule that exerts action on various bio-inorganic targets. Despite this importance, few studies have investigated the differential reactivity of the physiologically relevant H2S and HS- protonation states with metal complexes. Here we report the distinct reactivity of H2S 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 H2S, to generate [ZnPc-SH](-), which can be converted back to ZnPc by protonation. CoPc reacts with HS-, but not H2S, to form [(CoPc)-Pc-I](-), which can be reoxidized to CoPc by air. Taken together, these results demonstrate the chemically reversible reaction of HS- with metal phthalocyarnine complexes and highlight the importance of H2S protonation state in understanding the reactivity profile of H2S with biologically relevant metal scaffolds.