Light-driven hydrogen evolution system with glutamic-acid-modified zinc porphyrin as photosensitizer and [FeFe]-hydrogenase model as catalyst Pure Appl. Chem. 85, 1257–1513 (2013). A collection of invited papers based on presentations at the XXIVth IUPAC Symposium on Photochemistry, Coimbra, Portugal, 15–20 July 2012.

Abstract

An intermolecular light-driven hydrogen evolution system with free glutamic-acid-modified zinc tetra( p -phenyl) porphyrin ( Glu-ZnP ) as a photosensitizer and [Fe 2 (CO) 6 (μ-adt)C 6 H 5 ] [μ-adt = N(CH 2 S) 2 ] ( Badt ) as a catalyst has been constructed. Using phenylmercaptan ( BSH ) as electron donor and acetic acid (HOAc) as proton source, hydrogen was obtained after irradiation with visible light for 2 h; the efficiency is comparable to that of the similar intramolecular dyad. Steady-state and time-resolved spectroscopy and cyclic voltammetry show that both the first and the second electron transfer from singlet 1* Glu-ZnP to Badt and reduced Badt are thermodynamically feasible. However, the competition of electron transfer from singlet 1* Glu-ZnP to Badt with intersystem crossing from singlet 1* Glu-ZnP to triplet 3* Glu-ZnP , inefficient electron transfer from triplet 3* Glu-ZnP to Badt , and the lower energy of triplet 3* Glu-ZnP and possible 3* Badt to that of yielded charge-separated state of Glu-ZnP + · -Badt −· were believed to be the obstacles for efficient hydrogen evolution.