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MOLECULAR HYDROGEN PRODUCTION BY UROPORPHYRIN AND COPROPORPHYRIN: A MODEL FOR THE ORIGIN OF PHOTOSYNTHETIC FUNCTION
Author(s) -
Mercer–smith Janet A.,
Mauzerall David
Publication year - 1981
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1981.tb09016.x
Subject(s) - chemistry , porphyrin , photosynthesis , photochemistry , hydrogen production , artificial photosynthesis , aqueous solution , platinum , hydrogen , catalysis , inorganic chemistry , organic chemistry , biochemistry , photocatalysis
— Since life originated when the earth's atmosphere was still chemically reducing, the photooxidation of the prevalent reduced organic compounds and the emission of molecular hydrogen would have been a useful form of photosynthesis. If the biosynthetic pathway to chlorophyll recapitulates the evolutionary history of photosynthesis, then uroporphyrin served an early photosynthetic function. In the present study, ethylenediamine tetraacetic acid was oxidized by photoexcited uroporphyrin and coproporphyrin to produce molecular hydrogen in aqueous solution in the presence of colloidal platinum catalyst. In the presence of methyl viologen, a one‐electron carrier, the reaction is cyclic and hydrogen gas is produced at a constant rate. The evidence suggests that porphyrin radical intermediates rather than hydroporphyrin are active in the formation of molecular hydrogen. A coproporphyrin‐polyvinyl alcohol‐colloidal platinum polymer was used as a model for the evolving biological system for photosynthesis in which reactants are held in close proximity.