Tuning of the Electronic Structure and Reactivity of Metal Complexes with Redox‐Active Guanidine Ligands

Abstract Redox‐active ligands change more drastically the electronic structure of metal complexes than non‐redox‐active ligands, with consequences on the magnetic and optical properties as well as the (redox) reactivity. In this work, redox‐active guanidine ligands are integrated in cobalt and copper complexes. The variations in the electronic structures of cobalt complexes, in particular the relative energies of the states corresponding to high‐spin Co II or low‐spin Co III , in dependence of the redox‐active o ‐diguanidine ligand manifest themselves in different magnetic properties. Moreover, the electron transfer rates for copper complexes with two redox‐active diguanidino‐benzene ligands (self‐exchange betweeen a monocationic Cu I complex and the corresponding dicationic complex) were varied systematically over two orders of magnitude by choice of the redox‐active diguanidine ligand, realizing redox pairs with intermediate or record‐high rates.