Hydrogen sulfide (H 2S) 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 2S and HS – protonation states with metal complexes. Here we report the distinct reactivity of H 2S 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 2S, to generate [ZnPc-SH] −, which can be converted back to ZnPc by protonation. CoPc reacts with HS –, but not H 2S, to form [Co IPc] −, 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 2S protonation state in understanding the reactivity profile of H 2S with biologically relevant metal scaffolds.
The protonation state of H 2S influences its reactivity with different metal phthalocyanine (Pc) complexes. Both ZnPc and CoPc react with H 2S in a chemically reversible manner, with redox-inactive ZnPc binding HS − and redox-active CoPc undergoing reduction. The [ZnPc-SH] − product can be reverted to ZnPc by protonation, and [Co IPc] − can be redoxidized to CoPc with air.