Reactivity of Mono-Meso-Substituted Iron(II) Octaethylporphyrin Complexes with Hydrogen Peroxide in the Absence of Dioxygen. Evidence for Nucleophilic Attack on the Heme.

Kalish, Heather, Camp, Jason, Stepien, Marcin, Latos-Grazynski, Lechoslaw and Balch, Alan L. (2001) Reactivity of Mono-Meso-Substituted Iron(II) Octaethylporphyrin Complexes with Hydrogen Peroxide in the Absence of Dioxygen. Evidence for Nucleophilic Attack on the Heme. Journal of the American Chemical Society, 123 (47, Co). pp. 11719-11727. ISSN 0002-7863

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Abstract

Treatment of the mono-meso-substituted iron(II) octaethylporphyrin complexes, (py)2FeII(meso-NO2-OEP), (py)2FeII(meso-CN-OEP), (py)2FeII(meso-HC(O)-OEP), (py)2FeII(meso-Cl-OEP), (py)2FeII(meso-OMe-OEP), (py)2FeII(meso-Ph-OEP), and (py)2FeII(meso-Bu-OEP), with hydrogen peroxide in pyridine-d5 at -30° in the strict absence of dioxygen was monitored by 1H NMR spectroscopy. The product oxophlorin complexes are stable as long as the samples are protected from exposure to dioxygen. Hydrogen peroxide reacts cleanly with mono-meso-substituted iron(II) porphyrins in pyridine soln. under an inert atm. to form mixts. of three possible oxygenation products, (py)2Fe(cis-meso-R-OEPO), (py)2Fe(trans-meso-R-OEPO), and (py)2Fe(OEPO). The yields of (py)2Fe(OEPO), which results from replacement of the unique meso substituent, as a function of the identity of the meso substituent decrease in the order NO2 > HC(O) � CN � Cl > OMe > Ph, Bu, which suggests that the species responsible for attack on the porphyrin periphery is nucleophilic in nature. A mechanism involving isoporphyrin formation through attack of hydroxide ion on a cationic iron porphyrin with an oxidized porphyrin ring is suggested. The identity of the unique meso functionality also affects the regiospecificity of substitution when the unique meso group is retained. Although random attack at the two different meso sites is expected to yield a cis/trans product ratio of 2, the obsd. ratios vary in the following order: cyano, 5.0; Bu, 4.9; chloro, 3.2; formyl, 2.6; methoxy, 1.9; Ph 1.4. [on SciFinder(R)]

Item Type:	Article
Additional Information:	Unmapped bibliographic data: PY - 2001/// [EPrints field already has value set] M3 - 10.1021/ja011545b [Field not mapped to EPrints] JA - J. Am. Chem. Soc. [Field not mapped to EPrints]
Uncontrolled Keywords:	iron mono substituted porphyrinate reaction hydrogen peroxide, oxophlorinate iron isomer complex prepn
Subjects:	Q Science > Q Science (General) Q Science > QD Chemistry
Schools:	School of Applied Sciences
Related URLs:	Author
Depositing User:	Sara Taylor
Date Deposited:	15 Jan 2015 14:16
Last Modified:	28 Aug 2021 11:43
URI:	http://eprints.hud.ac.uk/id/eprint/22281

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