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Pure Appl. Chem., 2013, Vol. 85, No. 7, pp. 1405-1413

Published online 2013-01-19

Light-driven hydrogen evolution system with glutamic-acid-modified zinc porphyrin as photosensitizer and [FeFe]-hydrogenase model as catalyst

Shan Yu, Feng Wang, Jing-Jing Wang, Hong-Yan Wang, Bin Chen, Ke Feng, Chen-Ho Tung and Li-Zhu Wu*

Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, the Chinese Academy of Sciences, Beijing 100190, China

Abstract: An intermolecular light-driven hydrogen evolution system with free glutamic-acid-modified zinc tetra(p-phenyl) porphyrin (Glu-ZnP) as a photosensitizer and [Fe2(CO)6(μ-adt)C6H5] [μ-adt = N(CH2S)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.