Cooperativity in Dinuclear Complexes With Redox‐Active Guanidine Ligands Aligned in a Ring

Cooperative effects between interconnected metal complexes are the basis for a variety of new opportunities in catalysis and the design of switchable materials. In this work, redox‐active aromatic diguanidines were connected to ring structures through linkers at the guanidino groups. Dinuclear cobalt and copper complexes of these novel ligand systems were prepared. The analysis reveals differences in the electronic structure between the dinuclear complexes with interconnected diguanidine ligands and mononuclear reference complexes with unconnected diguanidine ligands, arising from cooperative effects between the complex units. A mixture of redox isomers is generated upon two‐electron oxidation of dinuclear high‐spin Co II complexes, In the case of dinuclear Cu complexes, equilibria are observed between redox isomers with Cu II atoms and reduced, neutral diguanidine units, and redox isomers with Cu I atoms and an unpaired electron on the partially oxidized guanidine units. Due to cooperative effects, the ratio of the redox isomers, estimated from EPR spectroscopy, varies with the linker between the redox‐active diguanidine units.