Redox-active ligands for chemical, electrochemical, and photochemical molecular conversions

• New synthetic and catalytic design with redox-active ligands/non-innocent ligands (RALs/NILs). • RALs/NILs is use for supplying and pooling multiple electrons and active hydrogen species. • RALs/NILs can act as spectators, moderators, suppliers/poolers, cooperators, or actors. • Excited-state hydrogen detachment (ESHD) as an alternative trigger for chemical reactions. • The ESHDs of a RAL/NIL realize various photochemical reactions in solution. • Chemical-, electrochemical- and photochemical activations of a RAL/NIL are described. A central issue in the design of reactions and catalysts based on metal complexes is the hybridization of functional ligands with metal atoms. Recent studies have demonstrated that redox-active/non-innocent ligands can potentially act as spectators, moderators, electron/H +/0/– supplier/poolers, cooperators, or actors, depending on their role(s) in the reaction. In this review, we will highlight selected stoichiometric or catalytic reactions driven by substituted ethylenes and dithiolenes, as well as six-membered ligands, such as catecholato, benezendithiolato, aminophenolato, and o -phenelyenediamine derivatives. Chemically, electrochemically, and photochemically induced lability of these ligands can be expected to provide an enriched recipe for a platform toward useful bond-activation and bond-formation processes.