TY - JOUR
T1 - Iron porphyrin-catalyzed reduction of CO2. Photochemical and radiation chemical studies
AU - Grodkowski, J.
AU - Behar, D.
AU - Neta, P.
AU - Hambright, P.
PY - 1997/1/16
Y1 - 1997/1/16
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=0030735107&partnerID=8YFLogxK
U2 - 10.1021/jp9628139
DO - 10.1021/jp9628139
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AN - SCOPUS:0030735107
SN - 1089-5639
VL - 101
SP - 248
EP - 254
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
IS - 3
ER -