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Indexed by:期刊论文

Date of Publication:2012-07-01

Journal:SCIENCE CHINA-CHEMISTRY

Included Journals:SCIE、EI

Volume:55

Issue:7

Page Number:1274-1282

ISSN No.:1674-7291

Key Words:cobaloxime; hydrogen production; molecular device; photocatalysis; zinc porphyrin

Abstract:Two new noble-metal-free molecular devices, [{Co(dmgH)(2)Cl}{Zn(PyTPP)}] (1, dmgH = dimethyloxime, PyTPP = 5-(4-pyridyl)-10,15,20-triphenylporphyrin) and [{Co(dmgH)(2)Cl}{Zn(apPyTPP)}] (2, apPyTPP = 5-[4-(isonicotinamidyl)phenyl]-10,15,20-triphenylporphyrin), for light-driven hydrogen generation were prepared and spectroscopically characterized. The zinc porphyrin photosensitizer and the Co-III-based catalyst unit are linked by axial coordination of a pyridyl group in the periphery of zinc-porphyrin to the cobalt centre of catalyst with different lengths of bridges. The apparent fluorescence quenching and lifetime decays of 1 and 2 were observed in comparison with their reference chromophores, Zn(PyTPP) (3) and Zn(apPyTPP) (4), suggesting a possibility for an intramolecular electron transfer from the singlet excited state of zinc porphyrin unit to the cobalt centre in the molecular devices. Photochemical H-2-evolving studies show that complexes 1 and 2 are efficient molecular photocatalysts for visible light-driven H-2 generation from water with triethylamine as a sacrificial electron donor in THF/H2O, with turnover numbers up to 46 and 35 for 1 and 2, respectively. In contrast to these molecular devices, the multicomponent catalyst of zinc porphyrin and [Co(dmgH)(2)PyCl] did not show any fluorescence quenching and as a consequence, no H-2 gas was detected by GC analysis in the presence of triethylamine with irradiation of visible light. The plausible mechanism for the photochemical H-2 generation with these molecular devices is discussed.