Iron porphyrin-catalyzed reduction of CO2. Photochemical and radiation chemical studies

J. Grodkowski, D. Behar, P. Neta*, P. Hambright

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

134 Scopus citations

Abstract

Several iron porphyrins have been reduced by photochemical and radiation chemical methods, in organic solvents and in aqueous solutions, from FeIIIP to FeIIP to FeIP and beyond. In aqueous solutions, the FeIP 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 FeIP state of tetrakis(N-methyl-3-pyridyl)porphyrin and tetrakis(N-methyl-4-pyridyl)-porphyrin are short-lived at any pH. Decay of FeIP is accelerated by H+ and by CO2, probably via reaction with the Fe0P state formed upon disproportionation of Fe1P. These reactions may lead to formation of H2 and CO, respectively, and to formation of the chlorin, FeIIPH2, as a side product. The FeIP 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 CO2 results in catalyzed reduction of CO2 to CO and formation of (CO)-FeIIP. The yield of free CO increases with time of photolysis and reaches turnover numbers of ∼70 molecules of CO per porphyrin molecule.

Original languageEnglish
Pages (from-to)248-254
Number of pages7
JournalJournal of Physical Chemistry A
Volume101
Issue number3
DOIs
StatePublished - 16 Jan 1997
Externally publishedYes

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