93085-16-6Relevant academic research and scientific papers
Resonance Raman study of a high-valent Fe=O porphyrin complex as a model for peroxidase compound II
Ishimaru, Hirohito,Fujii, Hiroshi,Ogura, Takashi
, p. 332 - 333 (2010)
Resonance Raman spectroscopy is applied to a FeIV oxo porphyrin with imidazolate as the axial ligand. The VFe=O mode is observed at 792 cm-1, which is 23 cm-1 lower than that of the analogous 1-methylimidazole complex and similar to that of horseradish peroxidase compound II (787 cm-1) at alkaline pH, for which presence of an anionic histidine was previously postulated. This study thus provides a useful model compound of horseradish peroxidase compound II.
Mechanisms of sulfoxidation catalyzed by high-valent intermediates of heme enzymes: Electron-transfer vs oxygen-transfer mechanism
Goto, Yoshio,Matsui, Toshitaka,Ozaki, Shin-ichi,Watanabe, Yoshihito,Fukuzumi, Shunichi
, p. 9497 - 9502 (1999)
Mechanisms of sulfoxidation catalyzed by high-valent intermediates of heme enzymes have been investigated by direct observation of sulfide-induced reduction of three different compound I species including HRP (horseradish peroxidase), the His64Ser myoglobin (Mb) mutant, and O=FeIVTMP+? (1) (TMP = 5,10,15,20-tetramesitylporphyrin dianion). The reaction of thioanisole and compound I of HRP (10 μM, pH 7.0, 298 K) gives the resting state of HRP with accumulation of compound II as an intermediate. The yield of sulfoxide by a stoichiometric reaction of HRP compound I with thioanisole was only 25% ± 5%. On the other hand, the same sulfoxidation by both 1 and His64Ser Mb compound I exclusively exhibited a two-electron process, resulting in quantitative formation of sulfoxide. When 1,5-dithiacyclooctane (DTCO) is employed as a substrate, the reaction of His64Ser Mb compound I with DTCO exhibits rapid formation of compound II, which decays to the ferric state due to the low oxidation potential of DTCO. The observed rate constants (log kobs) of the reactions of 1 and compounds I of HRP and His64Ser Mb with a series of p-substituted thioanisoles correlate with the one-electron oxidation potentials (E0ox) of the sulfides. A comparison of these correlations with the established correlation between log kobs and E0ox for the corresponding electron-transfer reactions of substituted N,N-dimethylanilines has revealed that the sulfoxidation reactions of compound I of HRP with the sulfides proceed via electron transfer while the sulfoxidations catalyzed by 1 and compound I of His64Ser Mb occur via direct oxygen transfer.
Bio-inspired nitrogen oxide (NOx) interconversion reactivities of synthetic heme Compound-I and Compound-II intermediates
Mondal, Pritam,Tolbert, Garrett B.,Wijeratne, Gayan B.
, (2021/11/11)
Dioxygen activating heme enzymes have long predicted to be powerhouses for nitrogen oxide interconversion, especially for nitric oxide (NO) oxidation which has far-reaching biological and/or environmental impacts. Lending credence, reactivity of NO with h
Mechanistic insight from thermal activation parameters for oxygenation reactions of different substrates with biomimetic iron porphyrin models for compounds i and II
Fertinger, Christoph,Franke, Alicja,Eldik, Rudi Van
scheme or table, p. 27 - 36 (2012/08/13)
Compound I, an oxo-iron(IV) porphyrin p-cation radical species, and its one-electron-reduced form compound II are regarded as key intermediates in reactions catalyzed by cytochrome P450. Although both reactive intermediates can be easily produced from model systems such as iron(III) meso-tetra(2,4,6- trimethylphenyl)porphyrin hydroxide by selecting appropriate reaction conditions, there are only a few thermal activation parameters reported for the reactions of compound I analogues, whereas such parameters for the reactions of compound II analogues have not been investigated so far. Our study demonstrates that DH= and DS= are closely related to the chemical nature of the substrate and the reactive intermediate (viz., compounds I and II) in epoxidation and C-H abstraction reactions. Although most studied reactions appear to be enthalpy-controlled (i.e., DH=[-TDS=), different results were found for C-H abstractions catalyzed by compound I. Whereas the reaction with 9,10-dihydroanthracene as a substrate is also dominated by the activation enthalpy (DH= = 42 kJ/mol, DS= = 41 J/Kmol), the same reaction with xanthene shows a large contribution from the activation entropy (DH= = 24 kJ/mol, DS= = -100 J/kmol). This is of special interest since the activation barrier for entropy-controlled reactions shows a significant dependence on temperature, which can have an important impact on the relative reaction rates. As a consequence, a close correlation between bond strength and reaction rate- as commonly assumed for C-H abstraction reactions-no longer exists. In this way, this study can contribute to a proper evaluation of experimental and computational data, and to a deeper understanding of mechanistic aspects that account for differences in the reactivity of compounds I and II. SBIC 2011.
Redox potentials of oxoiron(IV) porphyrin π-cation radical complexes: Participation of electron transfer process in oxygenation reactions
Takahashi, Akihiro,Kurahashi, Takuya,Fujii, Hiroshi
experimental part, p. 6922 - 6928 (2011/09/20)
The oxoiron(IV) porphyrin π-cation radical complex (compound I) has been identified as the key reactive intermediate of several heme enzymes and synthetic heme complexes. The redox properties of this reactive species are not yet well understood. Here, we report the results of a systematic study of the electrochemistry of oxoiron(IV) porphyrin π-cation radical complexes with various porphyrin structures and axial ligands in organic solvents at low temperatures. The cyclic voltammogram of (TMP)FeIVO, (TMP = 5,10,15,20-tetramesitylporphyrinate), exhibits two quasi-reversible redox waves at E1/2 = 0.88 and 1.18 V vs SCE in dichloromethane at -60 °C. Absorption spectral measurements for electrochemical oxidation at controlled potential clearly indicated that the first redox wave results from the (TMP)FeIVO/[(TMP+?)FeIVO]+ couple. The redox potential for the (TMP)FeIVO/[(TMP +?)FeIVO]+ couple undergoes a positive shift upon coordination of an anionic axial ligand but a negative shift upon coordination of a neutral axial ligand (imidazole). The negative shifts of the redox potential for the imidazole complexes are contrary to their high oxygenation activity. On the other hand, the electron-withdrawing effect of the meso-substituent shifts the redox potential in a positive direction. Comparison of the measured redox potentials and reaction rate constants for epoxidation of cyclooctene and demethylation of N,N-dimethylanilines enable us to discuss the details of the electron transfer process from substrates to the oxoiron(IV) porphyrin π-cation radical complex in the oxygenation mechanisms.
Direct Comparison of the reactivity of model complexes for compounds 0, I, and II in oxygenation, hydrogen-abstraction, and hydride-transfer processes
Fertinger, Christoph,Hessenaue-Ilicheva, Natalya,Franke, Alicja,Van Eldik, Rudi
body text, p. 13435 - 13440 (2010/06/11)
The iron(III) meso-tetramesitylporphyrin complex is a good biomimetic to study the catalytic reactions of cytochrome P450. All of the three most discussed reactive intermediates concerning P450 catalysis (namely, Cpd 0, Cpd I, and Cpd II) can be selective
Proton-directed redox control of O-O bond activation by heme hydroperoxidase models
Soper, Jake D.,Kryatov, Sergey V.,Rybak-Akimova, Elena V.,Nocera, Daniel G.
, p. 5069 - 5075 (2008/02/02)
Hangman metalloporphyrin complexes poise an acid-base group over a redox-active metal center and in doing so allow the pull effect of the secondary coordination environment of the heme cofactor of hydroperoxidase enzymes to be modeled. Stopped-flow investigations have been performed to decipher the influence of a proton-donor group on O-O bond activation. Low-temperature reactions of tetramesitylporphyrin (TMP) and Hangman iron complexes containing acid (HPX-CO2H) and methyl ester (HPX-CO 2Me) functional groups with peroxyacids generate high-valent Fe=O active sites. Reactions of peroxyacids with (TMP)FeIII(OH) and methyl ester Hangman (HPX-CO2Me)FeIII(OH) give both O-O heterolysis and homolysis products, Compound I (Cpd I) and Compound II (Cpd II), respectively. However, only the former is observed when the hanging group is the acid, (HPX-CO2H)FeIII(OH), because odd-electron homolytic O-O bond cleavage is inhibited. This proton-controlled, 2e- (heterolysis) vs 1e- (homolysis) redox specificity sheds light on the exceptional catalytic performance of the Hangman metalloporphyrin complexes and provides tangible benchmarks for using proton-coupled multielectron reactions to catalyze O-O bond-breaking and bond-making reactions.
Spontaneous Formation of Reactive Oxometal Porphyrins by Oxygen Atom Transfer from Dioxirane
Wolowiec, S.,Kochi, J. K.
, p. 1782 - 1784 (2007/10/02)
Oxygen atom transfer to manganese(II) tetraphenylporphyrin (tpp) and iron(II) tetramesitylporphyrin (tmp) is readily effected at IV(tpp) and O=Fe
Reactive Iron Porphyrin Derivatives Related to the Catalytic Cycles of Cytochrome P-450 and Peroxidase. Studies of the Mechanism of Oxygen Activation
Groves, John T.,Watanabe, Yoshihito
, p. 8443 - 8452 (2007/10/02)
The mechanism of oxidation of tetramesityliron(III) porphyrins IIITMP(X)> with peroxyacids has been examined.The reaction of FeIIITMP(Cl) (1) with peroxyacids in methylene chloride at -46 deg C afforded the corresponding oxoiron(IV) porphyrin cation radical IVTMP.+(O)> (3).The kinetics of this process were complicated by an induction period that depended on the acidity of the peroxyacid used.By contrast, similar oxidations of FeIIITMP(OH) gave evidence for rapid ligand metathesis to afford an acylperoxoiron(III) complex FeIIITMP(OOC(O)Ar) (2).The decomposition of 2 to form 3 was found to be first order in 2 and catalyzed by acid.Electron-withdrawing substituents on the aryl portion of the peroxyacid facilitated this reaction (ρ = +0.5).The temperature dependence between -32 and -48 deg C indicated Ea = 4 +/- 0.4 kcal/mol, ΔH* = 3.6 +/- 0.4 kcal/mol, and ΔS* > -25 eu.The oxidation of 1-(m-chlorobenzoate) in toluene with peroxyacids afforded an iron(III) porphyrin N-oxide (5).The reaction required 2 equiv of peroxyacid and afforded 1 mol of a diacylperoxide.The presence of acid discouraged the formation of 5.Substituent effects in the peroxyacid were the opposite for the formation of 5 (ρ = -0.4) than the formation of 3.The results indicated that there are competing homolytic and heterolytic O-O bond cleavage reactions for 2 mediated by iron(III).
