Mechanism of a one-photon two-electron process in photocatalytic hydrogen evolution from ascorbic acid with a cobalt chlorin complex

A one-photon two-electron process was made possible in photocatalytic H2 evolution from ascorbic acid with a cobalt(II) chlorin complex Co(II)(Ch) via electron transfer from ascorbate to the excited state of Ru(bpy)3(2+) followed by electron transfer from Ru(bpy)3(+) to Co(II)(Ch) with proton to give the hydride complex, which reacts with proton to produce H2. Co(III)(Ch)(+) was reduced by ascorbate to reproduce Co(II)(Ch).