After the electron transfers from the metal electrode to the Fe3+(H2O)(6) ion, the free energy of activation of this electron transfer reaction is calculated, then using the transition probability which is calculated ...After the electron transfers from the metal electrode to the Fe3+(H2O)(6) ion, the free energy of activation of this electron transfer reaction is calculated, then using the transition probability which is calculated by the perturbed degeneration theory and the Fermi golden rule,, the rate constant is gotten. Compared with the experimental results, it is satisfactory.展开更多
he electrochemistry of cytochrome C was investigated at a spectrographicgraphite electrode. In phosphate buffer solution (pH= 7. 0) , cytochrome C showedstable and quasi-reversible response. The formal potential E￣(o...he electrochemistry of cytochrome C was investigated at a spectrographicgraphite electrode. In phosphate buffer solution (pH= 7. 0) , cytochrome C showedstable and quasi-reversible response. The formal potential E￣(o') was 0. 015 V (at25℃ , vs. SCE) and the heterogeneous electron transfer rate constant k_s obtainedvaried form 1. 10×10￣(-3) cm · s￣(-1) to 1. 80k×10￣(-3) cm · s￣(-1). The thermodynamic pa-rameters of the electron transfer reaction of cvtochrome C was also estimated. Fur-thermore, the effect of the various electrode surface states on the electrochemistryof cytochrome C was discussed.展开更多
The electrochemical and the mass transport behavior of ABTS2-/ABTS＇- （2,2＇-azinobis（3- ethylbenzothiazoline-6-sulfonate）） redox couple at glassy carbon electrode （GCE） in phos- phate buffer solution （PBS, pH=...The electrochemical and the mass transport behavior of ABTS2-/ABTS＇- （2,2＇-azinobis（3- ethylbenzothiazoline-6-sulfonate）） redox couple at glassy carbon electrode （GCE） in phos- phate buffer solution （PBS, pH=4.4） is studied in detail by cyclic voltammetry combined with rotating disk electrode system. From the i-E curves recorded at different electrode rotating rate, rate constant, and transfer coefficient for ABTS 2-←→ABTS^-＋e reaction at GCE electrode and the diffusion coefficient of ABTS2- in PBS are estimated to be 4.6× 10^-3 cm/s, 0.28, and 4.4× 10^-6 cm^2/s, respectively. The transfer coefficient with a value of ca. 0.28 differs largely from the value of 0.5 that is always assumed in the literature. The origins for the difference of the rate constant determined and the challenges for estimating the stan- dard rate constant are discussed. The performance for such ABTS2- mediated bio-cathode toward oxygen reduction reaction is discussed according to the over-potential drop as well as current output limit associated with the charge transfer kinetics of ABTS2- ←→ABTS-＋e redox reaction and/or the mass transport effect.展开更多
Electron transfer (ET) reactions are of great importance to nearly every subdiscipline of chemistry. Marcus classical model, quantum model treating the nuclei as a quantum system, and the semiclassical model neglectin...Electron transfer (ET) reactions are of great importance to nearly every subdiscipline of chemistry. Marcus classical model, quantum model treating the nuclei as a quantum system, and the semiclassical model neglecting the nuclear tunneling effects but taking the nonadiabatic transition between two electronic states into account, have been widely used in the kinetic research of ET reactions. For the symmetric double-well potential vs. the nuclear configuration Q along the reaction path (fig.1(a)), a semiclassical kinetic model展开更多
After the separation of the donor, the acceptor, and the σ-type bridge from the π-σ-π system, the geometries of biphenyl, biphenyl anion radical, naphthalene, and naphthalene anion radical are optimized, and then ...After the separation of the donor, the acceptor, and the σ-type bridge from the π-σ-π system, the geometries of biphenyl, biphenyl anion radical, naphthalene, and naphthalene anion radical are optimized, and then the reorganization energy for the intermolecular electron transfer (ET) at the levels of HF/4-31G and HF/DZP is calculated. The ET matrix elements of the self-exchange reactions of theπ-σ-π systems have been calculated by means of both the direct calculation based on the variational principle, and the transition energy between the molecular orbitals at the linear coordinateR = 0.5. For the cross reactions, the ET matrix element and the geometry of the transition state are determined by searching the minimum energy splitting Δmin along the reaction coordinate. In the evaluation of the solvent reorganization energy of the ET in solution, the Marcus’ two- sphere model has been invoked. A few of ET rate constants for the intramolecular ET reactions for the π-σ-π systems, which contain the biphenylyl as the donor and both biphenylyl and naphthyl as the acceptor, have been obtained.展开更多
Electron transfer reaction between a simplified model molecule of α amino carbon centered radical and O 2 has been studied with ab initio calculations at the MP2/6 31++G ** //UHF/6 31++G ** leve...Electron transfer reaction between a simplified model molecule of α amino carbon centered radical and O 2 has been studied with ab initio calculations at the MP2/6 31++G ** //UHF/6 31++G ** level. The reactant complex and the ion pair complex have been optimized and employed to perform calculations of the reaction heat and the reorganization energy. Solvent effects have been considered by applying the conductor like screening model. Theoretical results show that the highly endothermic charge separation process, in which one electron transfers from the α amino carbon centered radical to O 2, so as to form an ion pair complex, is difficult to occur in gas phase. By applying an external electronic field to prepare the charge localized molecular orbitals, the charge separated state has been obtained using the initial guess induced self consistent field technique. The theoretical investigations indicate that the solvent effect in the process of the oxidation of α amino carbon centered radical by O 2 is remarkable. From the rate constant estimation, it can be predicted that the oxidation of the model donor molecule by O 2 can proceed, but not very fast. A peroxyl radical compound has been found to be a competitive intermediate in the oxidation process.展开更多
2,3,5,6-Tetrachloride-quinone was anchored to a gold surfare through the self-assem-bled monolayers of dithiol [DT HS-(CH2).-SH n=2,4,6,8,10]. The surface coverage of the anchoredTQ was esteminated to be 4.0 ×10-...2,3,5,6-Tetrachloride-quinone was anchored to a gold surfare through the self-assem-bled monolayers of dithiol [DT HS-(CH2).-SH n=2,4,6,8,10]. The surface coverage of the anchoredTQ was esteminated to be 4.0 ×10-11 mol’cm-2. The electron transfer rate constant Ket associatedwith the redox process of anchored film decreased from 6.75 s-1 at n=2 to 0.169 s-1 at n=10 withincreasing the chain length of the DT SAMs througth the redox potential of TQ. The turnningbarrier conefficient.(β) of the electron transfer was estimated to be 0.82A-1 from the observed linearrelationship between the Ket and the monolayer chain length.展开更多
A simple model for computing the electron transfer rate constant of a cross-reaction has been proposed in the framework of semiclassical theory and employed to investigate the electron transfer system NO2+/NO.The enco...A simple model for computing the electron transfer rate constant of a cross-reaction has been proposed in the framework of semiclassical theory and employed to investigate the electron transfer system NO2+/NO.The encounter complex of electron transfer NO2++NO→NO2+NO+has been optimized at the level of UHF/6-31G.In the construction of diabatic potential energy surfaces the linear coordinate was used and the kinetic quantities,such as the activation energies and the electron transfer matrix elements,have been obtained.For comparison,the related self-exchange reation systems NO2+/NO2 and NO+/NO were kinetically investigated.The calculated activation energies for the electron transfer reactions of systems NO2+/NO,NO2+/NO2,and NO+/NO are 81 4,128.8,and 39.8kJ mol-1,respectively With the solvent effect taken into account,the contribution of solvent reorganization to the activation energy has been estimated according to the geometric parameters of the transition states.The obtained rate constants show that the activity of NO2 as an oxidizing reagent in the aromatic nitration will be greatly decreased due to a high activation barrier contributed mainly from the change of bond angle ONO.展开更多
文摘After the electron transfers from the metal electrode to the Fe3+(H2O)(6) ion, the free energy of activation of this electron transfer reaction is calculated, then using the transition probability which is calculated by the perturbed degeneration theory and the Fermi golden rule,, the rate constant is gotten. Compared with the experimental results, it is satisfactory.
文摘he electrochemistry of cytochrome C was investigated at a spectrographicgraphite electrode. In phosphate buffer solution (pH= 7. 0) , cytochrome C showedstable and quasi-reversible response. The formal potential E￣(o') was 0. 015 V (at25℃ , vs. SCE) and the heterogeneous electron transfer rate constant k_s obtainedvaried form 1. 10×10￣(-3) cm · s￣(-1) to 1. 80k×10￣(-3) cm · s￣(-1). The thermodynamic pa-rameters of the electron transfer reaction of cvtochrome C was also estimated. Fur-thermore, the effect of the various electrode surface states on the electrochemistryof cytochrome C was discussed.
基金This work was supported by one hundred Talents＇ Program of the Chinese Academy of Science, the National Natural Science Foundation of China （No.21073176）, 973 Program from the Ministry of Science and Technology of China （No.2010CB923302）.
文摘The electrochemical and the mass transport behavior of ABTS2-/ABTS＇- （2,2＇-azinobis（3- ethylbenzothiazoline-6-sulfonate）） redox couple at glassy carbon electrode （GCE） in phos- phate buffer solution （PBS, pH=4.4） is studied in detail by cyclic voltammetry combined with rotating disk electrode system. From the i-E curves recorded at different electrode rotating rate, rate constant, and transfer coefficient for ABTS 2-←→ABTS^-＋e reaction at GCE electrode and the diffusion coefficient of ABTS2- in PBS are estimated to be 4.6× 10^-3 cm/s, 0.28, and 4.4× 10^-6 cm^2/s, respectively. The transfer coefficient with a value of ca. 0.28 differs largely from the value of 0.5 that is always assumed in the literature. The origins for the difference of the rate constant determined and the challenges for estimating the stan- dard rate constant are discussed. The performance for such ABTS2- mediated bio-cathode toward oxygen reduction reaction is discussed according to the over-potential drop as well as current output limit associated with the charge transfer kinetics of ABTS2- ←→ABTS-＋e redox reaction and/or the mass transport effect.
基金Project supported by the National Natural Science Foundation of China.
文摘Electron transfer (ET) reactions are of great importance to nearly every subdiscipline of chemistry. Marcus classical model, quantum model treating the nuclei as a quantum system, and the semiclassical model neglecting the nuclear tunneling effects but taking the nonadiabatic transition between two electronic states into account, have been widely used in the kinetic research of ET reactions. For the symmetric double-well potential vs. the nuclear configuration Q along the reaction path (fig.1(a)), a semiclassical kinetic model
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 29706104 and 29573112)the State Key Laboratory of Theoretical and Computational Chemistry of Jilin University.
文摘After the separation of the donor, the acceptor, and the σ-type bridge from the π-σ-π system, the geometries of biphenyl, biphenyl anion radical, naphthalene, and naphthalene anion radical are optimized, and then the reorganization energy for the intermolecular electron transfer (ET) at the levels of HF/4-31G and HF/DZP is calculated. The ET matrix elements of the self-exchange reactions of theπ-σ-π systems have been calculated by means of both the direct calculation based on the variational principle, and the transition energy between the molecular orbitals at the linear coordinateR = 0.5. For the cross reactions, the ET matrix element and the geometry of the transition state are determined by searching the minimum energy splitting Δmin along the reaction coordinate. In the evaluation of the solvent reorganization energy of the ET in solution, the Marcus’ two- sphere model has been invoked. A few of ET rate constants for the intramolecular ET reactions for the π-σ-π systems, which contain the biphenylyl as the donor and both biphenylyl and naphthyl as the acceptor, have been obtained.
文摘Electron transfer reaction between a simplified model molecule of α amino carbon centered radical and O 2 has been studied with ab initio calculations at the MP2/6 31++G ** //UHF/6 31++G ** level. The reactant complex and the ion pair complex have been optimized and employed to perform calculations of the reaction heat and the reorganization energy. Solvent effects have been considered by applying the conductor like screening model. Theoretical results show that the highly endothermic charge separation process, in which one electron transfers from the α amino carbon centered radical to O 2, so as to form an ion pair complex, is difficult to occur in gas phase. By applying an external electronic field to prepare the charge localized molecular orbitals, the charge separated state has been obtained using the initial guess induced self consistent field technique. The theoretical investigations indicate that the solvent effect in the process of the oxidation of α amino carbon centered radical by O 2 is remarkable. From the rate constant estimation, it can be predicted that the oxidation of the model donor molecule by O 2 can proceed, but not very fast. A peroxyl radical compound has been found to be a competitive intermediate in the oxidation process.
文摘2,3,5,6-Tetrachloride-quinone was anchored to a gold surfare through the self-assem-bled monolayers of dithiol [DT HS-(CH2).-SH n=2,4,6,8,10]. The surface coverage of the anchoredTQ was esteminated to be 4.0 ×10-11 mol’cm-2. The electron transfer rate constant Ket associatedwith the redox process of anchored film decreased from 6.75 s-1 at n=2 to 0.169 s-1 at n=10 withincreasing the chain length of the DT SAMs througth the redox potential of TQ. The turnningbarrier conefficient.(β) of the electron transfer was estimated to be 0.82A-1 from the observed linearrelationship between the Ket and the monolayer chain length.
基金Project supported by the National Natural Science Foundation of China
文摘A simple model for computing the electron transfer rate constant of a cross-reaction has been proposed in the framework of semiclassical theory and employed to investigate the electron transfer system NO2+/NO.The encounter complex of electron transfer NO2++NO→NO2+NO+has been optimized at the level of UHF/6-31G.In the construction of diabatic potential energy surfaces the linear coordinate was used and the kinetic quantities,such as the activation energies and the electron transfer matrix elements,have been obtained.For comparison,the related self-exchange reation systems NO2+/NO2 and NO+/NO were kinetically investigated.The calculated activation energies for the electron transfer reactions of systems NO2+/NO,NO2+/NO2,and NO+/NO are 81 4,128.8,and 39.8kJ mol-1,respectively With the solvent effect taken into account,the contribution of solvent reorganization to the activation energy has been estimated according to the geometric parameters of the transition states.The obtained rate constants show that the activity of NO2 as an oxidizing reagent in the aromatic nitration will be greatly decreased due to a high activation barrier contributed mainly from the change of bond angle ONO.
