Science China Chemistry

, Volume 55, Issue 7, pp 1274–1282

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

Articles

DOI: 10.1007/s11426-012-4514-0

Cite this article as:
Zhang, P., Wang, M., Li, X. et al. Sci. China Chem. (2012) 55: 1274. doi:10.1007/s11426-012-4514-0

Abstract

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 CoIII-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/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)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.

Keywords

cobaloxime hydrogen production molecular device photocatalysis zinc porphyrin 

Copyright information

© Science China Press and Springer-Verlag Berlin Heidelberg 2012

Authors and Affiliations

  1. 1.State Key Laboratory of Fine Chemicals; DUT-KTH Joint Education and Research Centre on Molecular DevicesDalian University of Technology (DUT)DalianChina
  2. 2.College of Environmental and Chemical EngineeringDalian UniversityDalianChina
  3. 3.Department of ChemistryRoyal Institute of Technology (KTH)StockholmSweden