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1.
The electron transfer (ET) reaction of aryl methyl sulfoxides with ruthenium(III)-polypyridine complexes is sensitive to the change of substituent in the aryl moiety of ArS(O)CH3 and ligand of Ru(III) complex. The detection of sulfoxide radical cation as the transient by conventional flash photolysis confirms ET in the rate-controlling step. The successful application of Marcus cross relation of ET leads to the evaluation of self-exchange rate constant of ArS+(O)CH3/ArS(O)CH3 as 4.0×105 M−1 s−1 similar to organic sulfides. Comparison with the reactivity of iron(III)-polypyridyl complexes points out that both reactivity and ρ values are higher with Ru(III) complexes.  相似文献   

2.
The oxidation of methionine (Met) plays an important role during biological conditions of oxidative stress as well as for protein stability. Ruthenium(III)–polypyridyl complexes, [Ru(NN)3]3+, generated from the photochemical oxidation of the corresponding Ru(II) complexes with molecular oxygen, undergo a facile electron transfer reaction with Met to form methionine sulfoxide (MetO) as the final product. Interaction of [Ru(NN)3]3+ with methionine leads to the formation of >S+● and (>S∴S<)+ species as intermediates during the course of the reaction. The interesting spectral, kinetic, and mechanistic study of the electron transfer reaction of four substituted methionines with six [Ru(NN)3]3+ ions carried out in aqueous CH3CN (1:1, v/v) by a spectrophotometric technique shows that the reaction rate is susceptible to the nature of the ligand in [Ru(NN)3]3+ and the structure of methionine. The rate constants calculated by the application of Marcus semiclassical theory to these redox reactions are in close agreement with the experimental values.  相似文献   

3.
The electron transfer kinetics of the reaction between the surfactant-cobalt(III) complex ions, cis-[Co(en)2(C12H25NH2)2]3+, cis-α-[Co(trien)(C12H25NH2)2]3+(en:ethylenediamine, trien:triethylenetetramine, C12H25NH2 : dodecylamine) by iron(II) in aqueous solution was studied at 298, 303, 308 K by spectrophotometry method under pseudo-first-order conditions using an excess of the reductant in self-micelles formed by the oxidant, cobalt(III) complex molecules, themselves. The rate constant of the electron transfer reaction depends on the initial concentration of the surfactant cobalt(III) complexes. ΔS# also varies with initial concentration of the surfactant cobalt(III) complexes. By assuming outer-sphere mechanism, the results have been explained based on the presence of aggregated structures containing cobalt(III) complexes at the surface of the self-micelles formed by the surfactant cobalt(III) complexes in the reaction medium. The rate constant of each complex increases with initial concentration of one of the reactants surfactant-cobalt(III) complex, which shows that self micelles formed by surfactant-cobalt(III) complex itself has much influence on these reactions. The electron transfer reaction of the surfactant-cobalt(III) complexes was also carried out in a medium of various concentrations of β-cyclodextrin. β-cyclodextrin retarded the rate of the reaction.  相似文献   

4.
The redox reactions of four iron(III)-polypyridyl complexes with six aryl methyl sulfoxides have been investigated by spectrophotometric technique. The reaction follows clean second order kinetics and proceeds through rate determining electron transfer (ET) from organic sulfoxides to iron(III). The Marcus cross-reaction relation has been applied to obtain the self exchange rate constant for the ArSOR/ArS+(O)R couple as 1.3×107 M−1 s−1. The application of Marcus theory to this ET reaction shows that the contribution of inner sphere reorganization energy is 0.4 eV. The rate constant and reaction constant values observed with organic sulfoxides are small compared with organic sulfides towards the same oxidant Fe(NN)33+.  相似文献   

5.
Reduction of [Ru2(CH3COO)2(C2O4)2(H2O)2]? by N-(2-hydroxyethyl)-ethylenediaminetriacetatoaquotitanium(III) [Ti(HEDTA)] involves several distinct stages. The first stage has a half-time of less than 1 ms, and is interpreted as a substitution reaction leading to a multinuclear intermediate. The second stage has a second-order rate constant of 5 x 103M?1s?1 [25°C, μ = 0.1 m (LiCF3SO3)]. The rate-limiting process for the second stage is electron transfer within the assembled multinuclear complex. Subsequent slower stages correspond to breakup of the multinuclear Ru(II)2-Ti(IV) complex formed by electron transfer. The overall rate of reduction of this oxidant by Ti(HEDTA) is less than the corresponding rate for the reaction in which Ti3+ acts as reductant, mainly because the stability of the binuclear complex is reduced by the presence of the aminoacid ligand. The data are consistent with the conclusion that the ligand increases the rate of intramolecular ET, probably by reducing geometric change associated with oxidation of Ti(III) to Ti(IV).  相似文献   

6.
The dynamics of the intramolecular electron transfer from Ru(II) to Ru(III) in binuclear mixedvalence complexes [(NH3)5Ru-L- Ru(NH3)5]5+ (L = N2,pyz, bipy, pym, bpa) is analyzed by the semiempirical CINDO +CI method. Translated fromZhumal Strukturnoi Khimii, Vol. 39, No. 4, pp. 579–590, July–August, 1998.  相似文献   

7.
Catalytic oxidation of water by Ru(bpy)3 3+ in the presence of Co2+ ions, well known in homogeneous solution, has been investigated in thin Nafion layers. Nafion layers on ITO electrodes were equilibrated with Ru(bpy)3 2+. Ru(bpy)3 3+ was produced by electrochemical oxidation after which the electrode was transferred into the reaction cell containing buffered Co2+ solution. The build up of Ru(bpy)3 2+ absorbance at 454 nm was followed spectrophotometrically. The reaction rate is proportional to [Ru(III)], [Co2+] and [HPO4 2-]. We found no evidence for a pH effect in the range 6–8, and no inhibition by Ru(II). A limiting rate of formation of Ru(II) is observed at high Co2+ or phosphate ion concentrations. At high local concentration of the Ru complex in the Nafion layer (~ 0.5 M), two Ru(II) formation processes are observed, their rates differ by one order, but other features (effects of [Ru(III)], [Ru(II)], [Co2+], phosphate and pH) remain unchanged. These results are in contrast with homogeneous solution where the rate of build up of Ru(II) has been previously reported to be proportional to [Ru(III)], [Co2+] and [OH-]2, and inversely proportional to [Ru(II)]. A mechanism is proposed which accounts for these observations.  相似文献   

8.
The photophysical and electron transfer properties of the lowest excited state of nine ruthenium (polypyridine) complexes have been characterized. The complexes studied are Ru (bpy)3-n (LL)2+n, where n varies from 0 to 3, and LL is 4, 4′-di-t-butyl-2,2′-bipyridine (DTB-bpy), 3, 3′-dimethyl-2, 2′-bipyridine (DM-bpy), or a 2, 2′-diquinolyl derivative (DMCH). The results obtained show that the Ru (bpy)2(DMCH)2+ complex is expected to be a more efficient mediator than Ru (bpy)2+3 in the water-splitting reaction by solar energy.  相似文献   

9.
Manganese(V)–oxo–porphyrins are produced by the electron‐transfer oxidation of manganese–porphyrins with tris(2,2′‐bipyridine)ruthenium(III) ([Ru(bpy)3]3+; 2 equiv) in acetonitrile (CH3CN) containing water. The rate constants of the electron‐transfer oxidation of manganese–porphyrins have been determined and evaluated in light of the Marcus theory of electron transfer. Addition of [Ru(bpy)3]3+ to a solution of olefins (styrene and cyclohexene) in CH3CN containing water in the presence of a catalytic amount of manganese–porphyrins afforded epoxides, diols, and aldehydes efficiently. Epoxides were converted to the corresponding diols by hydrolysis, and were further oxidized to the corresponding aldehydes. The turnover numbers vary significantly depending on the type of manganese–porphyrin used owing to the difference in their oxidation potentials and the steric bulkiness of the ligand. Ethylbenzene was also oxidized to 1‐phenylethanol using manganese–porphyrins as electron‐transfer catalysts. The oxygen source in the substrate oxygenation was confirmed to be water by using 18O‐labeled water. The rate constant of the reaction of the manganese(V)–oxo species with cyclohexene was determined directly under single‐turnover conditions by monitoring the increase in absorbance attributable to the manganese(III) species produced in the reaction with cyclohexene. It has been shown that the rate‐determining step in the catalytic electron‐transfer oxygenation of cyclohexene is electron transfer from [Ru(bpy)3]3+ to the manganese–porphyrins.  相似文献   

10.
Six new homobimetallic and heterobimetallic complexes of rhenium(I) and ruthenium(II) bridged by ethynylene spacer [(CO)3(bpy)Re(BL)Re(bpy)(CO)3]2+ [Cl(bpy)2Ru(BL)Ru(bpy)2Cl]2+ and [(CO)3(bpy)Re(BL)Ru(bpy)2Cl]2+ (bpy = 2,2′-bipyridine, BL = 1,2-bis(4-pyridyl)acetylene (bpa) and 1,4-bis(4-pyridyl)butadiyne (bpb) are synthesized and characterized. The electrochemical and photophysical properties of all the complexes show a weak interaction between two metal centers in heterobimetallic complexes. The excited state lifetime of the complexes is increased upon introduction of ethynylene spacer and the transient spectra show that this is due to delocalization of electron in the bridging ligand. Also, intramolecular energy transfer from *Re(I) to Ru(II) in Re–Ru heterobimetallic complexes occurs with a rate constant 4 × 107 s−1.  相似文献   

11.
Twelve ruthenium(III) complexes bearing amine-bis(phenolate) tripodal ligands of general formula [Ru(L1–L3)(X)(EPh3)2] (where L1–L3 are dianionic tridentate chelator) have been synthesized by the reaction of ruthenium(III) precursors [RuX3(EPh3)3] (where E = P, X = Cl; E = As, X = Cl or Br) and [RuBr3(PPh3)2(CH3OH)] with the tripodal tridentate ligands H2L1, H2L2 and H2L3 in benzene in 1:1 molar ratio. The newly synthesized complexes have been characterized by analytical (elemental and magnetic susceptibility) and spectral methods. The complexes are one electron paramagnetic (low-spin, d5) in nature. The EPR spectra of the powdered samples at RT and the liquid samples at LNT shows the presence of three different ‘g’ values (gx ≠ gy ≠ gz) indicate a rhombic distortion around the ruthenium ion. The redox potentials indicate that all the complexes undergo one electron transfer process. The catalytic activity of one of the complexes [Ru(pcr-chx)Br(AsPh3)2] was examined in the transfer hydrogenation of ketones and was found to be efficient with conversion up to 99% in the presence of isopropanol/KOH.  相似文献   

12.
Molecular hydrogen, detected by gas-chromatographic and mass-spectrometric measurements, was obtained by irradiating with visible light aqueous hydrochloridic solutions of [Ru(bpy)3]2+ and trivalent titanium. The active species is the 3CT of [Ru(bpy)3]2+, which is quenched by Ti(III). The suggested mechanism is an electron transfer with Ti(II) formation. The back reaction between [Ru(bpy)3]3+ and Ti(II) is hindered by the very fast competitive reaction of Ti(II) (not stable in acid aqueous solutions) with H+, carrying to hydrogen evolution.  相似文献   

13.
Redox reactions of Co(edta)? with Ru(NH3)5L2+ (L = 3- and 4-aminopyridine (AmPy)) were found to follow an outer-sphere electron transfer mechanism. The specific rate constants are (3.26 ± 0.03) × 102 and (3.07 ± 0.04) × 103 M?1S?1, for L = 3- and 4-AmPy, respectively, at μ, = 0.10 M LiClO4, pH = 8.0 (tris) and T = 25 °C. The rate constants of oxidations for a series of Ru(NH3)5L2+ complexes are higher than those of the corresponding Fe(CN)5L3- complexes by factors of 4 to 15 even after corrections for differences in reduction potentials and in charges of the complexes. Nonadiabaticity in the reactions of Fe(CN)5L3 complexes may account for the difference in the relative reactivities.  相似文献   

14.
The reactions of Fe(CN)5dpa3? and Ru(NH3)5dpa2+ (dpa = 4,4′-dipyridylamine) with Co(edta)? have been investigated kinetically. For Fe(CN)5dpa3? complex, a linear relationship was observed between the pseudo-First-order rate constants and the concentrations of Co(edta) which leads to a specific rate 0.876 ± 0.006 M?1S?1 at T = 25°C., μ = 0.10 M and pH = 8.0. For the Ru(NH3)5dpa2+ system, the plots kobs vs [Co(edta)?] become nonlinear at concentrations of Co(edta) greater than 0.01 M and the reaction is interpreted on the basis of a mechanism involving the formation of an ion pair between Ru(NH3)5dpa2+ and Co(edta)? followed by electron transfer from Ru(II) to Co(III). The nonlinear least squares fit of the kinetic results shows that Qip = 10.6 ± 0.7 M?1 and ket = 93.9 ± 0.7 s?1 at pH = 8.0,μ = 0.10 M and T = 25°C.  相似文献   

15.

Abstract  

The kinetics of the oxidation of ruthenium(III)-catalyzed oxidation of pentoxifylline (PTX) by diperiodatocuprate(III) (DPC) in aqueous alkaline medium at a constant ionic strength of 0.30 mol dm−3 was studied spectrophotometrically. The reaction between PTX and DPC in alkaline medium in the presence of Ru(III) exhibits 1:2 stoichiometry (PTX:DPC). The reaction was of first order in DPC, less than the unit order in [PTX] and [OH] and negative fractional order in [IO4 ]. The order in [Ru(III)] was unity. Intervention of free radicals was observed in the reaction. The main products were identified by TLC and spectral studies including LC-MS. The oxidation reaction in alkaline medium has been shown to proceed via a Ru(III)-PTX complex, which reacts with monoperiodatocuprate(III) to decompose in a rate determining step followed by a fast step to give the products. The reaction constants involved in different steps of the mechanism were calculated. The activation parameters with respect to the slow step of the mechanism were computed and discussed, and thermodynamic quantities were also determined. The active species of catalyst and oxidant have been identified.  相似文献   

16.
The kinetics and mechanism of reduction of the surfactant-cobalt(III) complex ions, cis-[Co(bpy)2(C12H25NH2)2]3+ and cis-[Co(phen)2(C12H25NH2)2]3+ (bpy = bipyridyl, phen = 1,10-phenan-throline, C12H25NH2 = dodecylamine) by Fe(CN6)4− in self-micelles were studied at different temperatures. Experimentally the reaction was found to be second order and the electron transfer postulated as outersphere. The rate constant for the electron transfer reaction for both the complexes was found to increase with increase in the initial concentration of the surfactant-cobalt(III) complex. This peculiar behaviour of dependence of second-order rate constant on the initial concentration of one of the reactants has been attributed to the presence of various concentration of micelles under different initial concentration of the surfactantcobalt(III) complexes in the reaction medium. The effect of inclusion of the long aliphatic chain of the surfactant complex ions into β-cyclodextrin on these reactions has also been studied.  相似文献   

17.
Conditions for the generation of the Ru(bpy)3 3+ complex in organic solvents (Me3CN or MeNO2) in the presence of small amounts of H2SO4 were found. Chemiluminescence was observed in the reaction of Ru(bpy)3 3+ with Ph3Na in a THF-MeCN mixture. The chemiluminescence emitter was identified as Ru(bpy)3 2+*. This emitter forms in the excited state in the elementary reaction of electron transfer from the Ph3C anion to Ru(bpy)3 3+. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 292–294, February, 1999.  相似文献   

18.
Monolayers of several surfactant analougues of Ru(bipy)23+ ha ve been deposited on SnO2 electrodes. Anodic photocurrents were observed when these electrodes were illuminated in (Ru-free) aqueous solutions. The photocurrents are interpreted by an electron transfer from the Ru(II) complex, excited to its triplet state, to the conduction band of SnO2. The Ru(III) complex formed in this reaction is efficiently reduced by water.  相似文献   

19.
The reaction of bromazepam (7‐bromo‐1,3‐dihydro‐5‐(2‐pyridyl)‐2H ‐1,4‐benzodiazepin‐2‐one, BZM) with Cr(III) ( 1 ), Fe(III) ( 2 ) and Ru(III) ( 3 ) salts gives complexes of the type [M(BZM)3]⋅3X (X = Cl or NO3). Structural characterization was extensively carried out using various analytical and spectral tools such as infrared, 1H NMR and UV–visible spectroscopies and magnetic, conductance, elemental and thermal analyses. BZM is a bidentate ligand and interacts with the metal ions via the pyridine and benzodiazepin‐2‐one nitrogen atoms. The magnetic and electronic properties of 2 and 3 are consistent with low‐spin octahedral complexes. The three BZM molecules are non‐isoenergetically coordinated to the metal ions and this is reflected in the values of the second‐order interaction energy. The antibacterial activity was studied using Staphylococcus aureus and Escherichia coli . Coordination of BZM to Cr(III) or Ru(III) ions leads to a marked increase in toxicity with respect to the inactive Fe(III) complex 2 .  相似文献   

20.
Manganese(III) sulfato complexes cause the oxidative degradation of methylene blue and its partially and fully N-demethylated derivatives, azure B and thionine dyes, respectively, in sulfuric acid media. The reaction proceeds through a colored reactive organic radical generated in the first stage via one-electron oxidation of the starting material, leading to a mixture of N-demethylated and/or deaminated species. The rates of formation of the methylene blue and azure B radicals are much higher than those of their further decomposition, whereas the generation of the thionine radical is much slower than its immeasurably fast decay. The kinetics of decomposition of all three dyes and the methylene blue and azure B radicals were studied spectrophotometrically under isolation conditions at 298 K. The first stage of each reaction proceeds according to a second-order rate expression, being first order in the dyes and in the manganese(III) concentrations. Dependence of the pseudo-first-order rate constants on the oxidant concentration for the second stage exhibits a saturation effect under the applied conditions. It is postulated that electron transfer takes place between the [Mn(SO4)3]3− complex and the protonated form of the dye. The reactivity order of the dyes as determined from the second-order rate constants for the first reaction stage corresponds to the order of their HOMO energies.  相似文献   

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