15158-62-0Relevant articles and documents
Migration reactivities of a-bonded ligands of organoiron and organocobalt porphyrins depending on different high oxidation states
Fukuzumi, Shunichi
, p. 5000 - 5006 (1999)
Migration reactivities of σ-bonded organo-iron and -cobalt porphyrins were examined as a function of the compound oxidation state. Migration rates were determined for both the one-electron and two-electron oxidized species produced in the electron-transfer oxidation with different oxidants in acetonitrile at 298 K. The investigated compounds are represented as [(OETPP)Fe(R)]n+, where n = 1 or 2, OETPP = the dianion of 2,3,7,8,12,13,-17,18-octaethyl-5,10,15,20-tetraphenylporphyrin, and R = C6H5, 3,5-C6F2H3, or C6F5, and as [(TPP)Co(R)]n+, where n = 1 or 2, TPP = the dianion of 5,10,15,20-tetraphenylporphyrin, and R = CH3 or C6H5. The rapid two-electron oxidation of (OETPP)FeIII(R) occurs with [Ru(bpy)3]3+ (bpy = 2,2′-bipyridine) to produce [(OETPP)-FeIV(R)]2+. The formation of this species is followed by a slow migration of the σ-bonded R group to a nitrogen of the porphyrin ring to give [(N-ROETPP)FeII]2+ and then by a rapid electron-transfer oxidation of the migrated product with [Ru(bpy)3]3+ to yield [(N-ROETPP)FeIII]3+ as a final product. When [Ru(bpy)3]3+ is replaced by a much weaker oxidant such as ferricenium ion, only the one-electron oxidation of (OETPP)Fe(R) occurs to produce [(OETPP)FeIV(R)]+. A migration of the R group also occurs in the one-electron oxidized porphyrin species, [(OETPP)FeIV(R)]+, to produce [(N-ROETPP)FeII]+, which is rapidly oxidized by ferricenium ion to yield [(N-ROETPP)FeIII]2+. The migration rate of the R group in [(OETPP)FeIV(R)]+ is about 104 times slower than the migration rate of the corresponding two-electron oxidized species, [(OETPP)FeIV(R)]2+. The migration rate of the σ-bonded ligand of [(TPP)CoIV(R)]+, produced by the one-electron oxidation of (TPP)CoIII(R) with [Fe-(phen)3]3+ (phen = 1,10-phenanthroline) is also about 104 times slower than the migration rate of the R group in the corresponding two-electron oxidized species, [(TPP)CoIV(R)]2+, which is produced by the two-electron oxidation with [Ru(bpy)3]3+. A comparison of the migration rates with the oxidation states of the porphyrins indicates that the migration occurs via an intramolecular electron transfer from the R group to the Fe(IV) or Co(IV) metal of the organometallic porphyrin.
An all-inorganic, stable, and highly active tetraruthenium homogeneous catalyst for water oxidation
Geletii, Yurii V.,Botar, Bogdan,Koegerler, Paul,Hillesheim, Daniel A.,Musaev, Djamaladdin G.,Hill, Craig L.
, p. 3896 - 3899 (2009/02/08)
(Chemical Equation Presented) Oxidation without organics: A tetraruthenium polyoxometalate (see picture; Ru blue, O red, Si yellow, W black) catalyzes the rapid oxidation of H2O to O2 in water at ambient temperature, and shows considerable stability under turnover conditions. The complex was characterized by several methods, including X-ray crystallography and cyclic voltammetry.
New experimental data and mechanistic studies on the bromate-dual substrate-dual catalyst batch oscillator
Szalai, Istvan,Kurin-Csoergei, Krisztina,Horvath, Viktor,Orban, Miklos
, p. 6067 - 6072 (2008/10/09)
The bromate-hypophosphite-acetone-Mn(II)-Ru(bpy)32+ batch oscillator was recently suggested for studying two-dimensional pattern formation. The system meets all major requirements that are needed for generation of good quality traveling waves in a thin solution layer. The serious drawback of using the system for studying, temporal and spatial dynamical phenomena is its unknown chemical mechanism. In order to develop a mechanism that explains the observed long-lasting batch oscillations the bromate-hypophosphite-acetone-Mn(II)-Ru(bpy)32+ oscillator was revisited. We studied the dynamics both in the total system and in some composite reactions, and kinetic measurements were carried out in three subsystems. From the new experimental results we concluded that the two oscillatory sequences observed in the full system are originated from two oscillatory subsystems, the Mn(II)-catalyzed bromate-hypophosphite-acetone and the Ru(bpy)32+-catalyzed bromate-bromoacetone reactions. Here we propose a mechanism which is capable of simulating the dynamical features that appeared in the complex system.
Electron-transfer kinetics for generation of organoiron(IV) porphyrins and the iron(IV) porphyrin π radical cations
Fukuzumi, Shunichi,Nakanishi, Ikuo,Tanaka, Keiko,Suenobu, Tomoyoshi,Tabard, Alain,Guilard, Roger,Van Caemelbecke, Eric,Kadish, Karl M.
, p. 785 - 790 (2007/10/03)
Homogeneous electron-transfer kinetics for the oxidation of seven different iron(III) porphyrins using three different oxidants were examined in deaerated acetonitrile, and the resulting data were evaluated in light of the Marcus theory of electron transfer to determine reorganization energies of the rate-determining oxidation of iron(III) to iron(IV). The investigated compounds are represented as (P)Fe(R), where P = the dianion of 2,3,7,8,12,13,17,18-octaethyl-5,10,15,20-tetraphenylporphyrin (OETPP) and R = C6H5, 3,5-C6F2H3, 2,4,6-C6F3H2, or C6F5 or P = the dianion of 2,3,7,8,12,13,17,18-octaethylporphyrin (OEP) and R = C6H5, 2,4,6-C6F3H2, or 2,3,5,6-C6F4H. The first one-electron transfer from (P)Fe(R) to [Ru(bpy)3]3+ (bpy = 2,2'-bipyridine) leads to an Fe(IV) σ-bonded complex, [(P)Fe(IV)(R)]+, and occurs at a rate which is much slower than the second one-electron transfer from [(P)Fe(IV)(R)]+ tO [Ru(bpy)3]3+ to give [(P)Fe(IV)(R)]·2+. The one- or two-electron oxidation of each (OETPP)Fe(R) or (OEP)Fe(R) derivative was also attained by using [Fe(phen)3]3+ (phen = 1,10-phenanthroline) or [Fe(4,7-Me2phen)3]3+ (Me2phen = 4,7-dimethyl- 1,10-phenanthroline) as an electron-transfer oxidant. The reorganization energies (kcal mol-1) for the metal-centered oxidation of (P)Fe(III)(R) to [CP)Fe(IV)(R)]+ increase in the order (OEP)Fe(R) (83 ± 4) 6F5) (99 ± 2) 6F3H2) (107 ± 2) 6F2H3) (109 ± 3) 6H5) (113 ± 3). Each value is significantly larger than the reorganization energies determined for the porphyrin-centered oxidations involving the same two series of compounds, i.e., the second electron transfer of (P)Fe(R). In each case, the first metal-centered oxidation is the rate-determining step for generation of the iron(IV) porphyrin π radical cation. Coordination of pyridine to (OETPP)Fe(C6F5) as a sixth axial ligand enhances significantly the rate of electron-transfer oxidation.
Oxidative homolysis of organochromium macrocycles
Steffan, Carl R.,Espenson, James H.,Bakac, Andreja
, p. 1134 - 1137 (2008/10/08)
The complexes RCrL(H2O)2+ (R = alkyl, aralkyl; L = 1,4,8,12-tetraazacyclopentadecane) are oxidized by Ru(bpy)33+ and 2E Cr(bpy)33+. The one-electron oxidized species RCrL(H2O)3+ undergoes subsequent homolysis; the R. radicals so produced may react with certain metal complexes, or they dimerize, depending on conditions. The rate constants for the rate-controlling step, electron transfer from RCrL(H2O)2+ to Ru(bpy)33+ or *Cr(bpy)33+, were measured by laser flash photolysis for an extensive range of R groups. For Ru(bpy)33+, the rate constants range from 14.2 L mol-1 s-1 (R = CH3) to 1.05 × 109 (R = 4-CH3C6H4CH2); for *Cr(bpy)33+, the corresponding values are 2.8 × 106 and 1.55 × 109 L mol-1 s-1. In both series, the order of rate constants is methyl . are linear, in accord with the rate-controlling step being electron transfer.
Electron-Transfer Quenching of Ruthenium(II) Photosensitizers by Mercury(II) in Aqueous Nitrate Media
Hauenstein, B. L.,Dressick, W. J.,Demas, J. N.,DeGraff, B. A.
, p. 2418 - 2422 (2007/10/02)
Excited-state interactions of tris(α-diimine)ruthenium(II) photosensitizers with Hg2+ were studied in aqueous nitrate media by using luminescence qyenching and flash photolysis methods.Quenching proceeds via oxidative electron transfer to yield Ru(III) and a Hg(I) free radical with high effenciency.Regardless of the excited-state reducing power of the photosensitizer, quenching was near but below the Marcus diffusion-controlled limit.Dimerization of the Hg(I) free radical to give Hg22+ competes effectively with the diffusion-limited back-electron-transfer reaction of the free radical with the Ru(III) species.The back-reaction rate of Hg22+ and Ru(III) is much slower and depends on E0(Ru(III/II)).The efficiency of electron-transferred-product separation is sensitive to E0(Ru(III/II)).The mechanism of the oxidation of Hg22+ by Ru(III) is discussed.
