Photophysics of Fe-Fe hydrogenase mimic complexes for hydrogen evolution

Molecular Dyad vs Multi‐Component Approach‐Photocatalytic Hydrogen Evolution by Combining Oligothiophene Photosensitizers with [FeFe]‐Hydrogenase Mimics

“…This could be an indication for contributions of an additional state to the overall spectral signature, i. e. a superposition of the signature of the thiophene located 3 ππ* state with signatures of a second excited state, e. g. a CS state or a 3 MC state as postulated above based on the calculations. Taking into account characteristic spectroscopic signatures reported for the reduced CAT (absorption bands at around e. g. 700 nm) [12,15] and the reported short lifetime [14] as well as the calculated spectroscopic signature of the 3 MC state (supporting information Figure S23), contributions of a CS state having CAT *À nature seems to be more likely. Additionally, the decay of the transient signal of PS-CAT reveals two decay components with lifetimes of t 1 = 33.5 μs and t 2 = 16.6 μs.…”

“…However, a very recent paper by the Weinstein group reported that the lifetime of the 3 MC state of the [FeFe]-hydrogenase mimic is only on the picosecond scale. [14] Therefore such an EnT process, if occurring, is unlikely to contribute to a catalytic cycle requiring a reaction with an external electron/proton donor in a diffusion limited bimolecular reaction. In addition, an electron transfer pathway is possible upon ISC originating from S 2 .…”