The dinuclear PhotoCORM (CO)3(bpy)ReMn(CO)5. formation of a luminactive product upon CO uncaging by MMLCT excitation

We report a photochemical investigation of the dinuclear metal carbonyl complex (CO)3(bpy)ReMn(CO)5, where bpy = 2,2′-bipyridine. This investigation follows an earlier study of the photo-activated carbon monoxide release as the result of long-wavelength visible and near-infrared excitation of a several different (CO)5ReMn(CO)3(LL) complexes in aerobic media. These dinuclear species all show a strong metal − metal-bond (σMM)-to-ligand (πL*) charge-transfer (MMLCT) bands as the lowest energy absorptions in their respective optical spectra. Photolysis of the MMLCT band leads to homolysis of the metal-metal bond to give mononuclear metal radicals that can be trapped with dioxygen. The species formed from the manganese carbonyl radical fragments undergo CO release via secondary reactions, while the mononuclear product(s) formed from the •Re(CO)3(bpy) radical is luminescent. In these contexts, we discuss potential applications of such dinuclear compounds as photoactivated CO-releasing moieties.