Copper Complexes of New Redox-Active 4,5-Bisguanidino-Substituted Benzodioxole Ligands: Control of the Electronic Structure by Counter-Ligands, Solvent, and Temperature.

Herein, we analyze the possibility of controlling the electronic structure of mononuclear copper complexes featuring new redox-active 4,5-bisguanidino-substituted benzodioxole ligands. The nature of the guanidino groups, the anionic counter-ligands, the applied solvent (polarity), and the temperature are the parameters that decide if a CuII complex with neutral ligand unit or a CuI complex with radical monocationic ligand unit is the adequate description. Under special conditions, a temperature-dependent equilibrium of the two valence tautomeric forms (CuII /neutral ligand and CuI /radical monocationic ligand) is achieved. Removal of a ligand-centered electron from a paramagnetic CuII complex with a neutral ligand unit leads to a diamagnetic CuI complex with a dicationic ligand unit through a redox-induced electron-transfer (RIET) process.