Fine‐Tuning Redox Properties of Heteroleptic Molybdenum Complexes through Ligand‐Ligand‐Cooperativity

Heteroleptic molybdenum complexes bearing 1,5‐diaza‐3,7‐diphosphacyclooctane (P₂N₂) and non‐innocent dithiolene ligands were synthesized and electrochemically characterized. The reduction potentials of the complexes were found to be fine‐tuned by a synergistic effect identified by DFT calculations as ligand‐ligand cooperativity via non‐covalent interactions. This finding is supported by electrochemical studies combined with UV/Vis spectroscopy and temperature‐dependent NMR spectroscopy. The observed behavior is reminiscent of enzymatic redox modulation using second ligand sphere effects.

Ligand-ligand cooperativity is introduced as a novel option for fine-tuning redox properties of molecular complexes. The effect was found when combining dithiolene and 1,5-diaza-3,7-diphosphacyclooctane ligands in one complex. During electrochemical measurements, a non-covalent interaction in the second ligand-sphere results in an electronic conversation between both ligands, which has an unprecedented impact on the observed redox transitions.