Iron tetrakis porphyrin

Water soluble iron porphyrins [Fem(TPPS)(H20) ]3-330 and [Fem(TMPy)(H20)2]5+ 331 332 (TPPS = maso-tetrakis(/ -sulfonatophenyl)porphyrin, TMPyP = / /e.vo-tetrakis(7V-methyl-4-pyridi-nium)porphyrin331 or maso-tetrakis (A -methyl-2-pyridinium)porphyrin332 dications) act as effective electrocatalysts for the reduction of nitrite to ammonia in aqueous electrolytes (Equation (64) Ei/2= 0.103 V vs. SCE at pH 7), with NH2OH or N20 also appearing as products depending on the reaction conditions. Nitric oxide then ligates to the iron(III) porphyrin to form a nitrosyl complex [Fen(P)(NO+)] (P = porphyrin) as intermediate. 

The kinetics and mechanism for oxygen transfer between 4-cyano-V,V,-dimethylaniline V-oxide and a C2-capped mexo-tetraphenylporphyrinatoiron(III) and mc5 o-tetrakis(pentafiuorophenyl)-porphyrinatoiron(III) have been established. Addition of a copper(II) porphyrin cap to an iron(II)-porphyrin complex has the expected effect of reducing both the affinities and rate constants for addition of dioxygen or carbon monoxide. These systems were studied for tetradecyl-substituted derivatives solubilized by surfactants such as poly(ethylene oxide) octaphenyl ether. ... 

Iron(II) meso-tetrakis(2,4,6-trimethoxyphenyl)porphyrin and the triethoxy analogue have been synthesized by Vaska. These are different to the capped and picket fence porphyrins in that both sides of the porphyrin are sterically hindered. Dioxygen uptake by these iron(II) porphyrins at 25 °C in solution was found to be partially reversible. La Mar and co-workers166 have shown that the porphyrins Fe[T(2,4,6-OMe)3PP], Fe[T(2,4,6-OEt)3PP] and Fe[TpivPP] take up oxygen at low temperatures, in the absence of a base such as Melm or pyridine, to give dioxygen adducts of the... 

The kinetics of oxidation of aldehydes by the Fenton reagent [Fe(II)-H202-0H-] have been studied.89 It has been suggested that different reactivities of PhIO in iron(III)-porphyrin-catalysed alkene epoxidation may be due to the formation of a more reactive iron(IV)-0-IPh complex.90 The iron(m) complex of tetrakis(3,5-disulfonato-mesityl)porphyrin catalyses the oxidative degradation of 2,4,6-trichlorophenol to 2,6-dichloro-l,4-benzoquinone with KHSO5 as the oxygen atom donor a peroxidase-type oxidation is thought to be involved.91... 

Exclusive enone formation could be achieved by electrocatalytic oxygenation of 2-cyclopentene-l-acetic acid in the presence of a water-soluble iron(III) porphyrin (2-TMPyP)Fe [2-TMPyP =tetrakis(N-methyl-2-pyridyl)porphyrin]. Unfortunately, neither yields nor TONs are given [116]. 

An iron(III) porphyrin complex, (P8 )Fein(H20)2 (Px = tetra-ferf-butyl-tetrakis [2,2-bis(carboxylato)ethyl]-5,10,15,20-tetraphenylporphyrin), reacts reversibly with NO39 to form the nitrosyl complex. 

Iron tetra(p-methylpyridinium)porphyrin (T(p-M)PyP) Iron tetrakis(3-sulfonatophenyl)porphyrin (TPPS)... 

X 10 M at 25 °C). Lack of splitting of the H NMR signals of o- and m-phenyl protons of [TPPFeF2] supports the assumption of diaxial fluoride coordination with the metal in the plane of the porphyrin. In aqueous solution at high pH, water-soluble iron(III) porphyrins such as tetrakis(o-methylpyridinium)porphyrin, T(o-MPy)PFe , bind two hydroxide ions and give rise to a characteristic v no Fe H resonance Raman band at 447 cm ... 

The bis(base) (where base = tV-methylimidazole, 1,5-dicyclohexylimidazole, pyridine) complexes of FeII(TpivPP), where TpivPP = tetrakis(o-pivalamidophe-nyl)porphyrin, give characteristic porphyrinate ligand bands.218 Resonance Raman spectra were used to obtain excitation profiles for two a2g ligand modes for a range of iron(II) porphyrins.219 Ligand modes in the resonance Raman spectra of trarax-cross-linked basket-handle iron(II) porphyrins were used to characterise the ruffled, six-coordinated low-spin iron(II) porphyrin complexes.220... 

Our initial approach was to use [(TMPA)Cu(RCN)]+ (TMPA = tris[2-pyridylmethyl]-amine) (1), and the reduced iron(II) porphyrins (F8-TPP)Fe(II)-B2, B = pyridine, piperidine, Fg-TPP = tetrakis(2,6-difIuoropheny])porphyrin) in the presence of molecular... 

The oxidation of OH by [Fe(CN)6] in solution has been examined. Application of an electrical potential drives the reaction electrochemically, rather than merely generating a local concentration of OH at the anode, as has been suggested previously, to produce both O and [Fe(CN)6] in the vicinity of the same electrode. With high [OH ] or [Fe(CN)6] /[Fe(CN)6] ratio, the reaction proceeds spontaneously with a second-order rate constant of 2.2 x 10 M s at 25 °C. Under anaerobic conditions, iron(III) porphyrin complexes in dimethyl sulfoxide solution are reduced to the iron(II) state by addition of hydroxide ion or alkoxide ions. Excess hydroxide ion serves to generate the hydroxoiron(II) complex. The oxidation of hydroxide and phenoxide ions in acetonitrile has been characterized electrochemically " in the presence of transition metal complexes [Mn(II)L] [M = Fe,Mn,Co,Ni L = (OPPh2)4,(bipy)3] and metalloporphyrins, M(por) [M = Mn(III), Fe(III), Co(II) por = 5,10,15,20-tetraphenylpor-phinato(2-), 5,10,15,20-tetrakis(2,6-dichlorophenyl)porphinato(2-)]. Shifts to less positive potentials for OH and PhO are suggested to be due to the stabilization of the oxy radical products (OH and PhO ) via a covalent bond. Oxidation is facilitated by an ECE mechanism when OH is in excess. 

In order to estabHsh the relationship between the structure of the prosthetic group and its reactivity toward NO in various hemoproteins in vivo, many efforts have been devoted to reveal the influence of the porphyrin microenvironment in the iron(III) porphyrin systems (i.e., the identity and charge of the substituents in the porphyrin periphery) on the dynamics of both the binding and release of nitric oxide. In this context, several new water-soluble iron(III) porphyrin models, i.e., a highly negatively charged ((P )Fe = [5", 115", 20" -tetra-ief i-butyl-5, 5 , 15, 15 -tetrakis-(2,2-biscarboxylato-ethyl)-... 

Shi, C. and F. C. Anson (1990). Catalytic pathways for the electroreduction of oxygen by iron tetrakis(4-iV-methylpyridyl)porphyrin or iron tetraphenylporphyrin adsorbed on edge plane pyrolytic graphite electrodes. Inorg. Chem. 29, 4298-4305. 

Bruice, T.C. and G. He (1991). Nature of the epoxidizing species generated by reaction of aUcyl hydroperoxides with iron(III) porphyrins. Oxidations of cis-stilbene and (Z)-l,2-bis(trans-2, trans-3-diphenylcyclopropyl)ethene by tert-BuOOH in the presence of [meso-tetrakis(2,4,6-trimethylphenyl)porphinato]-, [meso-tetrakis(2,6-dichlorophenyl)-porphinato]-, and [meso-tetrakis(2,6-dibromophenyl)porphinato]rron(III) chloride. J. Am. Chem. Soc. 113, 2747-2753. 

The temperature dependence of the catalyst activity of an iron fluoro-porphyrin-coated graphite electrode was studied by RDE coupled with the surface cyclic voltammetry. The purpose was to investigate the surface adsorption and reaction, O2 reduction catalysis kinetics, and especially the temperature effect on the catalyst activity. Figure 7.11(A) shows the surface CVs of 5,10,15,20-Tetrakis(pentafluorophenyl)-21H,23H-porphine iron (III) chloride (abbreviated as Fe TPFPP)-coated graphite electrode, recorded in a pH 1.0 Ar-saturated solution at different potential scan rates. The 1-electron reversible redox peak of approximately 0.35 V can be seen, which has a peak current increased linearly with increasing the potential scan rate, indicating the electrochemical behavior of this peak follows the feature of a reversible redox reaction of an adsorbed species on the electrode surface. 

The conclusions from the theoretical investigations reported above [ 180] were experimentally confirmed when iron tetrakis(2,6-difluorophenyl)porphyrin was assembled on imidazole-fnnctionalized carbon nanotubes (Im-CNTs) through coordination with the imidazole group (Scheme 14.10, [201]). In fact, this catalyst displayed higher ORR activity, superior stability, and excellent methanol tolerance in comparison to the commercial Pt/C catalyst. 

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