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1.
Yu Okubo Yuta Kido Ryoko Fujiyoshi Takashi Sumiyoshi 《Radiation Physics and Chemistry》2009,78(12):1161-1163
Photochemical reactions of organic sulfur compounds (CH3SCH3, C2H5SCH3 and C2H5SC2H5)–chlorine atom complexes have been studied using a combined pulse radiolysis-laser flash photolysis technique. Excitation of all complexes has resulted in photobleaching with a similar quantum yield (0.37±0.07), independent of solvent polarities and concentration of solutes. The results were compared with previous studies of the analogous dimethyl sulfoxide (DMSO)–Cl complexes. It is concluded that the significant change of photobleaching quantum yields of the excited DMSO–Cl complex observed in the DMSO-CCl4 mixed solvent is mainly due to the specific solvation effect of DMSO for cations. 相似文献
2.
The decay kinetics of hydrated electron (eaq
−) formed upon photolysis of aqueous solutions of sodium pyrene-1,3,6,8-tetrasulfonate at λ = 337 nm in the presence of phosphate
anions (up to 2 mol L−1) was studied by nanosecond laser-pulse photolysis in a wide range of pH (3.5–10) and ionic strength (I, up to 2 mol L−1) values. At high pH values, where the HPO4
2− ions dominate, the eaq
− decay kinetics depends only slightly on phosphate concentration (rate constant for the reaction is at most 2·105 L mol−1 s−1). The H2PO4
− ions react with eaq
− at a rate constant of 2.8·106 L mol−1 s−1 (I = 0), which increases linearly with the parameter
in accordance with the Debye-Hückel theory. The rate constant for quenching of eaq
− by H3PO4 at pH ≤ 4 decreases linearly with the parameter
due to the secondary salt effect and equals 1.6·109 L mol−1 s−1 at I = 0. The logarithm of the rate constant for quenching of eaq
− by phosphates is linearly related to the number of the O-H bonds in the phosphate molecule.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1277–1280, July, 2007. 相似文献
3.
K. Kalyanasundaram 《Journal of Chemical Sciences》1992,104(6):701-712
Applications of laser flash photolysis techniques are illustrated using three specific cases among many photoprocesses involving
transition metal polypyridyl complexes (LL = bpy, phen or related ligands): dynamics of photoinduced formation of complexes
of the type M(CO)4(LL), where M = Mo0, Cr0 or W0; dynamics of photosubstitution reactions of Ru(LL)
3
2 +
and photoredox reactions of MLCT excited states of RuII(LL)
3
2+
and [ReI(CO)3(Cl)(LL)]. 相似文献
4.
O. A. Snytnikova P. S. Sherin L. V. Kopylova Yu. P. Tsentalovich 《Russian Chemical Bulletin》2007,56(4):732-738
Photochemical reactions involving kynurenines, viz., molecules present in the eye lens, can result in modifications of the lens proteins and cause a development of a cataract.
The rate constants of the reactions of photoexcited kynurenine with several amino acids and antioxidants contained in the
lens were measured. The most efficient quenchers of triplet kynurenine are amino acids tryptophan and tyrosine, as well as
antioxidant ascorbate. In all cases, the quenching reaction proceeds by the electron transfer mechanism, except for the reaction
with oxygen where transfer of the triplet energy to the oxygen molecule occurs.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 704–710, April, 2007. 相似文献
5.
Milica Kosović Željko Jaćimović Živadin D Bugarčić 《Journal of Coordination Chemistry》2015,68(17-18):3003-3012
Substitution reactions of five monofunctional Pd(II) complexes, [Pd(terpy)Cl]+ (terpy = 2,2′;6′,2″-terpyridine), [Pd(bpma)Cl]+ (bpma = bis(2-pyridylmethyl)amine), [Pd(dien)Cl]+ (dien = diethylenetriamine or 1,5-diamino-3-azapentane), [Pd(Me4dien)Cl]+ (Me4dien = 1,1,7,7-tetramethyldiethylenetriamine), and [Pd(Et4dien)Cl]+ (Et4dien = 1,1,7,7-tetraethyldiethylenetriamine), with unsaturated N-heterocycles such as 3-amino-4-iodo-pyrazole (pzI), 5-amino-4-bromo-3-methyl-pyrazole (pzBr), 1,2,4-triazole, pyrazole, pyrazine, and imidazole were investigated in aqueous 0.10 M NaClO4 in the presence of 10 mM NaCl using variable-temperature stopped-flow spectrophotometry. The second-order rate constants k2 indicate that the reactivity of the Pd(II) complexes decrease in the order [Pd(terpy)Cl]+ > [Pd(bpma)Cl]+ > [Pd(dien)Cl]+ > [Pd(Me4dien)Cl]+ > [Pd(Et4dien)Cl]+. The most reactive nucleophile of the heterocycles is pyrazine, while the slowest reactivity is with pyrazole. Activation parameters were determined for all reactions and negative entropies of activation, ΔS≠, supporting an associative mode of substitution. The reactions between [Pd(bpma)Cl]+ and 1,2,4-triazole, pzI, and pzBr were also investigated by 1H NMR to define the manner of coordination. These results could be useful for better explanation of structure-reactivity relationships of Pd(II) complexes as well as for the prediction of potential targets of Pd(II) complexes toward common N-heterocycles, constituents of biomolecules and different N-bonding pharmaceutical agents. 相似文献
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7.
Wu Feng Deng Nansheng E. M. Glebov I. P. Pozdnyakov V. P. Grivin V. F. Plyusnin N. M. Bazhin 《Russian Chemical Bulletin》2007,56(5):900-903
The formation of MV•+ radical cations was observed upon the laser flash photolysis of the iron(III) tartrate complex [FeIIITart]+ (1) in the presence of methyl viologen (MV2+). The rate constants of the reactions involving MV•+ were measured. The intramolecular electron trans-fer to form FeII and escape of the organic radical to the solvent bulk upon the photolysis of 1 were proposed.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 866–869, May, 2007. 相似文献
8.
Tachikawa T Tojo S Fujitsuka M Majima T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(29):7585-7594
The photocatalytic one-electron oxidation reactions of aromatic sulfides using the carboxymethyl-beta-cyclodextrin (CM-beta-CD)-modified TiO(2) nanoparticles (TiO(2)/CM-beta-CD) were investigated by using nano- and femtosecond transient absorption spectroscopies. The one-electron oxidation processes of the substrate (S) by the valence band hole (h(VB) (+)) at the TiO(2) surface and the trapped hole at the adsorption site of the CM-beta-CD (h(CD) (+)) were examined. The transient absorption spectra and time traces observed for the charge carriers and the radical cation of S (S(.+)) revealed that the one-electron oxidation reaction of S during the nano- and femtosecond laser flash photolyses of TiO(2)/CM-beta-CD is significantly enhanced relative to bare TiO(2). The kinetics of the decay and the dimerization processes between S(.+)s are discussed on the basis of the results obtained by the pulse radiolysis technique. 相似文献
9.
pH Dependence of Photochemical Kinetics of Thioxanthen-9-one from Nanosecond Time-Resolved Laser Flash Photolysis 下载免费PDF全文
pH dependent fluorescence emission of a thioxanthone-based probe has been reported recently. The potential determinant factors of pH dependence may provide important clues to design novel thioxanthone-based probes in the future. pH dependence of photochemical kinetics of thioxanthone itself was investigated in this work using nanosecond time-resolved laser flash photolysis. The nanosecond time-resolved transient absorption spectra and kinetics of TX in aqueous acetonitrile were recorded, as well as for a model reaction system including TX with diphenylamine (DPA) as a co-initiator. Besides the well-known absorption peak of \begin{document}$ ^3 $\end{document} TX\begin{document}$ ^* $\end{document} , other peaks at 417, 518, 673 and 780 nm, have been reliably attributed to major intermediates in the overall reaction between TX and DPA with photolysis, which has been confirmed to occur along a multistep process. In the strong acidic solution (pH\begin{document}$ \approx $\end{document} 3.0), TX and protonated TX ions (TXH\begin{document}$ ^+ $\end{document} ) coexist due to protonated equilibrium. Consequently, high proton concentration promotes the predominant decay pathway after photolysis from electron transfer to proton affinity. Subsequently, the different primary products, \begin{document}$ ^3 $\end{document} TXH\begin{document}$ ^{+*} $\end{document} or TX\begin{document}$ ^{\bullet-} $\end{document} , proceed different secondary reaction channels. In addition, within the wide pH range from weak acid (pH = 5.0) to alkaline solution (pH = 13.0), the overall reaction mechanism and rates do not show visible changes. 相似文献
10.
首次用脉冲辐解时间分辨方法研究了etoposide(VP16)在水溶液中与N~3^.,(SCN)~2^.^-和e~a~q^-之间发生的单电子氧化还原反应,测定了VP16的阴离子自由基、脱质子中性自由基的特征吸收谱;测得VP16与e~a~q^-,N~3^.,(SCN)~2^.^-的绝对反应速率常数分别为2.7×10^9,3.2×10^9和2.5×10^8dm^3.mol^-^1.s^-^1。研究表明,水溶液中的VP16可为248nm激光光电离,光电离的瞬态产物为阳离子自由基及脱质子中性自由基,并且测定了其酸碱电离的pK值。测得SO~4^.^-自由基单电子氧化VP16的反应速率常数为2.8×10^9dm^3.mol^-^1.s^-^1。 相似文献
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12.
Nazarov A. M. Khursan S. L. Chainikova E. M. Komissarov V. D. 《Russian Chemical Bulletin》2002,51(4):608-615
The kinetics of the reactions of acetic, benzoic, formic, oxalic, malic, tartaric, trifluoroacetic, and hydrochloric acids with diphenylcarbonyl oxide Ph2COO was studied. The carbonyl oxide Ph2COO was generated by flash photolysis of diphenyldiazomethane Ph2CN2 in solutions of acetonitrile and benzene at 295 K. The apparent rate constants of the reaction range from 4.6·108 for (COOH)2 in MeCN to 7.5·109 L mol–1 s–1 for acetic acid in a benzene solution. The reaction mechanism was proposed, according to which at the first stage the carbonyl oxide is reversibly solvated by the solvent. Then the solvated carbonyl oxide reacts with the acid molecule by the mechanism of insertion at the O—H bond. 相似文献
13.
A. M. Nazarov E. M. Chainikova P. V. Krupin S. L. Khursan I. A. Kalinichenko V. D. Komissarov 《Russian Chemical Bulletin》2000,49(9):1496-1500
The kinetics of the reactions of diphenylcarbonyl oxide with dimethyl, di-n-hexyl, diphenyl, dibenzyl, andn-hexylbenzyl sulfoxides in acetonitrile was studied by flash photolysis at 295 K. The oxidation of sulfoxide affords the corresponding
sulfone as the main reaction product, and diphenyl sulfide also forms in the case of Ph2SO. Solvent effect on the reaction kinetics and the composition of the reaction products was studied. The reaction mechanism
is discussed, which includes two parallel pathways: the nucleophilic attack of carbonyl oxide at the sulfur atom of sulfoxide
and the formation of the cyclic sulfurane intermediatevia the electrophilic 1,3-cycloaddition of Ph2COO at the S=O bond. The sulfurane undergoes fragmentationvia parallel channels to form sulfone or sulfide.
Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1504–1509, September, 2000. 相似文献
14.
Photoinduced electron transfer reactions of several electron-deficient olefins with N,N,N′,N′-tetramethylbenzidine (TMB) in acetonitrile solution have been studied by using laser flash photolysis technique and steady-state fluorescence quenching method. Laser pulse excitation of TMB yields 3TMB* after rapid intersystem crossing from 1TMB*. The triplet which located at 480 nm is found to undergo fast quenching with the electron acceptors fumaronitrile (FN), dimethyl fumarate (DMF), diethyl fumarate (DEF), cinnamonitrile (CN), -acetoxyacrylonitrile (AAN), crotononitrile (CrN) and 3-methoxyacrylonitrile (MAN). Substituents binding to olefin molecule own different electron-donating/withdrawing powers, which determine the electron-deficient property (π-cloud density) of olefin molecule as well as control the electron transfer rate constant directly. The detection of ion radical intermediates in the photolysis reactions confirms the proposed electron transfer mechanism, as expected from thermodynamics. The quenching rate constants of triplet TMB by these olefins have been determined at 510 nm to avoid the disturbance of formed TMB cation radical around 475 nm. All the values approach or reach to the diffusion-controlled limit. In addition, fluorescence quenching rate constants have been also obtained by calculating with Stern–Volmer equation. A correlation between experimental electron transfer rate constants and free energy changes has been explained by Marcus theory of adiabatic outer-sphere electron transfer. Disharmonic kq values for CN and CrN in endergonic region may be the disturbance of exciplexs formation. 相似文献
15.
Cai X Sakamoto M Fujitsuka M Majima T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(22):6471-6477
The lifetimes of benzophenone in the higher triplet excited state (BP(T(n))) and several BP derivatives in the T(n) states were measured directly to be tau(T(n))=37+/-7 ps and 20-33 ps, respectively, by using the nanosecond-picosecond (ns-ps) two-color/two-laser flash photolysis method. Based on the direct measurements of tau(T(n)) of BP(T(n)), the triplet energy transfer (TET) from BP(T(n)) to quenchers (Q), such as carbon tetrachloride (CCl4), benzene (Bz), and p-dichlorbenzene (DCB), was investigated. The fast TET from BP(T(n)) to Q can be attributed to the lifetime-dependent quenching process, according to the Ware theoretical model of the bimolecular energy transfer reaction. The contribution of the lifetime-dependent term on k(TET) was 27, 60, and 86% for CCl4, Bz, and DCB as the Q of BP(T(n)), respectively, indicating that the TET from BP(T(n)) to Q is influenced not only by tau(T(n)), but also by the size of Q. 相似文献
16.
Zhang R Harischandra DN Newcomb M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(19):5713-5720
Corrole-manganese(V)-oxo intermediates were produced by laser flash photolysis of the corresponding corrole-manganese(IV) chlorate complexes, and the kinetics of their decay reactions in CH2Cl2 and their reactions with organic reductants were studied. The corrole ligands studied were 5,10,15-tris(pentafluorophenyl)corrole (H3TPFC), 5,10,15-triphenylcorrole (H3TPC), and 5,15-bis(pentafluorophenyl)-10-(p-methoxyphenyl)corrole (H3BPFMC). In self-decay reactions and in reactions with substrates, the order of reactivity of (Cor)Mn(V)(O) was TPC > BPFMC > TPFC, which is inverted from that expected based on the electron-demand of the ligands. The rates of reactions of (Cor)Mn(V)(O) were dependent on the concentration of the oxidant and other manganese species, with increasing concentrations of various manganese species resulting in decreasing rates of reactions, and the apparent rate constant for reaction of (TPFC)Mn(V)(O) with triphenylamine was found to display fractional order with respect to the manganese-oxo species. The kinetic results are consistent in part with a reaction model involving disproportionation of (Cor)Mn(V)(O) to give (Cor)Mn(IV) and (Cor)Mn(VI)(O) species, the latter of which is the active oxidant. Alternatively, the results are consistent with oxidation by (Cor)Mn(V)(O) which is reversibly sequestered in non-reactive complexes by various manganese species. 相似文献
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19.
ZHU Hongping ZHANG Zhaoxia ZHAO Hongwei WANG Wenfeng & YAO Side . Shanghai Institute of Applied Physics Chinese Academy of Sciences Shanghai China . Graduate University of the Chinese Academy of Sciences Beijing China 《中国科学B辑(英文版)》2006,49(4):308-314
Reactive oxygen species (ROS) are generated dur- ing radiation, respiratory burst, normal metabolic processes and so on. There are enzymatic and non-enzymatic antioxidants such as superoxide dis- mutase (SOD), glutathione peroxidase (GSH-Px), vi- tamin E (VE) and carotenoids that can either inhibit or repair the ROS-induced damage. ROS is essential to maintain physiological homeostasis. However, exces- sive ROS give rise to oxidative damage to proteins, lipids and DNA which related t… 相似文献
20.
Visible light irradiation of the [(η-C6H7)Fe(η-C6H6)]+ cation (1) in CH2Cl2 in the presence of alkyl-substituted benzenes results in arene exchange forming the [(η5-C6H7)Fe(η-C6R6)]+ cations (2a–d: C6R6 is toluene, p-xylene, mesitylene, and durene). The mixed bis(arene) [(η-C6H6)Fe(η-C6R6)]2+ iron complexes (3a–d) were synthesized by hydride ion abstraction from 2a–d by [Ph3C]+.
Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1864–1865, September, 2007. 相似文献