An unprecedented single crystal-to-single crystal transformation occurs when a binuclear oxovanadium(V) compound [(V2O2)-O-V(L)(2)] 1 involving 2,6-bis(hydroxymethyl)-p-cresol (H3L) as a bridging ligand is exposed simultaneously to white light and aerial oxygen to generate an oligomeric compound [(V2O2)-O-IV(L*)(2)] 2 (H2L* is 3-hydroxymethyl-5-methylsalicylaldehyde). Each vanadium(V) center in 1 is reduced to vanadium(IV) in 2 at the expense of a two-electron alcohol-to-aldehyde oxidation in the coordinated ligand. The additional electron being released is possibly consumed by molecular oxygen to generate hydrogen peroxide.