Iron porphyrin-catalyzed reduction of CO{sub 2}. Photochemical and radiation chemical studies
- National Inst. of Standards and Technology, Gaithersburg, MD (United States)
- Howard Univ., Washington, DC (United States)
Several iron porphyrins have been reduced by photochemical and radiation chemical methods, in organic solvents and in aqueous solutions, from Fe{sup III}P to Fe{sup II}P to Fe{sup I}P and beyond. In aqueous solutions, the Fe{sup I}P state is relatively stable for the tetrakis(N-methyl-2-pyridyl)porphyrin at high pH but is shorter lived in neutral and acidic solutions. The Fe{sup I}P state of tetrakis(N-methyl-3-pyridyl)porphyrin and tetrakis(N-methyl-4-pyridyl)-porphyrin are short-lived at any pH. Decay of Fe{sup I}P is accelerated by H{sup +} and by CO{sub 2}, probably via reaction with the Fe{sup 0}P state formed upon disproportionation of Fe{sup I}P. These reactions may lead to formation of H{sub 2} and CO, respectively, and to formation of the chlorin, Fe{sup II}PH{sub 2}, as a side product. The Fe{sup I}P state is also observed as a stable product in several organic solvents. This is observed by photolysis of iron tetraphenylporphyrin and several of its derivatives (e.g., trimethyl-, dichloro- and pentafluorophenyl), mainly in dimethylformamide and acetonitrile solutions, using triethylamine as a reductive quencher. Further photoreduction in the presence of CO{sub 2} results in catalyzed reduction of CO{sub 2} to CO and formation of (CO)-Fe{sup II}P. The yield of free CO increases with time of photolysis and reaches turnover numbers of approximately 70 molecules of CO per porphyrin molecule. 29 refs., 4 figs.
- OSTI ID:
- 501922
- Journal Information:
- Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory, Journal Name: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory Journal Issue: 3 Vol. 101; ISSN 1089-5639; ISSN JPCAFH
- Country of Publication:
- United States
- Language:
- English
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