Probing chemical reduction in a cobalt(III) complex as a viable route for the inhibition of the 20S proteasome

► Ligand dissociation following biological reduction was evaluated in [CoIII(L1)2]ClO4. ► DFT calculations to evaluate phenolate-to-cobalt(III) LMCT band at 440 nm. ► Spectroelectrochemical and chemical reduction characterization to monitor LMCT. ► Products support that reduction leads to ligand dissociation.