Photochemical hydrogen production with molecular devices comprising a zinc porphyrin and a cobaloxime catalyst  

作　　者：ZHANG Pan WANG Mei LI XueQiang CUI HongGuang DONG JingFeng SUN LiCheng 

机构地区：[1]State Key Laboratory of Fine Chemicals,DUT-KTIt Joint Education and Research Centre on Molecular Devices Dalian University of Technology(DUT),Dalian 116012,China [2]College of Environmental and Chemical Engineering,Dalian University,Dalian 116622,China [3]Department of Chemistry,Royal Institute of Technology(KTH),Stockholm 10044,Sweden

出　　处：《Science China Chemistry》2012年第7期1274-1282,共9页中国科学（化学英文版）

基　　金：supported by the National Natural Science Foundation of China (20633020);the National Basic Research Program of China(2009CB220009);the Swedish Energy Agency;the Swedish Research Council;the K & A Wallenberg Foundation

摘　　要：Two new noble-metal-free molecular devices, [{Co（dmgH）2Cl}{Zn（PyTPP）}] （1, dmgH = dimethyloxime, PyTPP = 5-（4- pyridyl）-10,15,20-triphenylporphyrin） and [{Co（dmgH）2Cl}{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 H2-evolving studies show that complexes 1 and 2 are efficient molecular photocatalysts for visible light-driven H2 generation from water with triethylamine as a sacrificial electron donor in THF/H20, 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）2PyCl] did not show any fluorescence quenching and as a consequence, no H2 gas was detected by GC analysis in the presence of triethylamine with irradiation of visible light. The plausible mechanism for the photochemical H2 generation with these molecular devices is discussed.Two new noble-metal-free molecular devices,[{Co(dmgH) 2 Cl}{Zn(PyTPP)}](1,dmgH = dimethyloxime,PyTPP = 5-(4pyridyl)-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 H2-evolving studies show that complexes 1 and 2 are efficient molecular photocatalysts for visible light-driven H2 generation from water with triethylamine as a sacrificial electron donor in THF/H2 O,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 H2 gas was detected by GC analysis in the presence of triethylamine with irradiation of visible light.The plausible mechanism for the photochemical H2 generation with these molecular devices is discussed.

关 键 词：COBALOXIME hydrogen production molecular device PHOTOCATALYSIS zinc porphyrin 

分 类 号：O627.23[理学—有机化学] TN204[理学—化学]