Redox chemistry and photophysics of the [V(dgpy)2]3+/2+ redox pair

Abstract

Transition-metal complexes with earth-abundant metal centers hold significant potential for light-induced processes. Pseudo-octahedral vanadium(III) and vanadium(II) complexes with d2 and d3 electron configurations are promising candidates, yet their redox and excited-state properties are only insufficiently understood. Here, we combine quantum chemistry and experimental data (structure, cyclic voltammetry, spectroelectrochemistry, electron-transfer dissociation, collision-induced dissociation, ultraviolet photodissociation mass spectrometry, and ultrafast transient absorption spectroscopy) to elucidate redox and photostability as well as excited-state lifetimes of the vanadium(III/II) redox couple cisfac -[V(dgpy)2]3+/2+ (dgpy = 2,6-diguanidylpyridine). Ground-state splitting, mixing of spin-flip excited states with metal-to-ligand charge transfer states, and multiphonon relaxation are identified as the key challenges for excited-state lifetimes in these d2/d3 systems.