title: Fast Hydrogen Atom Abstraction by a Hydroxo Iron(III) Porphyrazine.
abstract: A reactive hydroxoferric porphyrazine complex, [(PyPz)FeIII(OH) (OH2)]4+(1, PyPz = tetramethyl-2,3-pyridino porphyrazine), has been prepared via one-electron oxidation of the corresponding ferrous species [(PyPz)FeII(OH2)2]4+(2). Electrochemical analysis revealed a pH-dependent and remarkably high FeIII-OH/FeII-OH2reduction potential of 680 mV vs Ag/AgCl at pH 5.2. Nernstian behavior from pH 2 to pH 8 indicates a one-proton, one-electron interconversion throughout that range. The O-H bond dissociation energy of the FeII-OH2complex was estimated to be 84 kcal mol-1. Accordingly, 1 reacts rapidly with a panel of substrates via C-H hydrogen atom transfer (HAT), reducing 1 to [(PyPz)FeII(OH2)2]4+(2). The second-order rate constant for the reaction of [(PyPz)FeIII(OH) (OH2)]4+with xanthene was 2.22 × 103M-1s-1, 5-6 orders of magnitude faster than other reported FeIII-OH complexes and faster than many ferryl complexes.
authors.affiliation: Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States.
authors.forename: Hongxin
authors.initials: H
authors.lastname: Gao
authors.affiliation: Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States.
authors.forename: John T
authors.identifier: 0000-0002-9944-5899
authors.initials: JT
authors.lastname: Groves
mesh_terms: D055664:Electrochemical Techniques; D019277:Entropy; D005296:Ferrous Compounds / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D015394:Molecular Structure; D011166:Porphyrins / Q000737:chemistry*
chemical_list: D005296:Ferrous Compounds; D011166:Porphyrins; D006859:Hydrogen