From Fundamental Chemistry to Biological Function: The Biological and Abiological Chemistry of Metal Persulfides and Related Species

Biological sulfur species have emerged as versatile mediators of redox chemistry, linking thiol-based signaling, oxidative stress response, and metabolic regulation. Among these species, persulfides (RSSH) occupy a unique chemical niche defined by both nucleophilic and electrophilic reactivity, tunable acidity, and capacity for dynamic sulfur exchange and transfer reactions. Persulfides are now recognized as central participants in H2S signaling pathways, metal–sulfur cofactor biosynthesis, and sulfur trafficking processes that sustain cellular homeostasis. Our coverage of the biological and abiological chemistry of metal persulfide species focuses on examples in protein-based systems in which metal persulfide motifs are generated and on synthetic small molecule model systems ranging from isolated and characterized persulfides to metal-containing persulfide motifs. We focus on integrating recent advances in the mechanistic chemistry and biological function of metal-bound persulfides and highlight how protonation state, local microenvironment, coordination mode, and metal identity can modulate persulfide reactivity from bioinorganic motifs to small molecule model systems. Complementing this coverage, we also highlight emerging insights into related selenium systems to showcase both the similarities and differences between these two important biological chalcogens.