Marcus电子转移理论的科学性探讨

利用科学原理对Marcus电子转移理论的科学性进行了考察, 结果表明Marcus电子转移理论违背了能量守恒定律.     

一类有机体系分子内电子转移反应的理论研究

对1984年Miller和Closs设计的有机分子内电子转移反应体系的反应速率常数进行了直接理论计算研究,获得与实验值接近的结果,理论计算结果进一步证明了体系中反转区的存在.     

Non-Condon效应对电子转移速率影响的理论模拟及其在有机半导体中的应用

随着Condon近似下各种电子转移理论的不断发展与完善和人们对non-Condon效应在电子转移过程中重要作用认识的逐步深入,已建立了几个理论模型来研究这种效应对电子转移速率的影响.本文主要总结了近两年来我们在non-Condon效应电子转移理论方面的工作,首先阐述了指数型、高斯型以及直线型non-Condon电子转移速率的全量子表达式,然后运用该理论模型以及分子动力学模拟计算了二噻吩四硫富瓦烯（DT-TTF）有机半导体的迁移率.此外,还进一步利用数值模拟详细研究了这三种线型的non-Condon效应在量子尺度上对电子转移速率的影响.     

二氯二氰基苯醌及其阴离子自交换电子转移反应的理论研究

基于非平衡溶剂化能的约束平衡方法和溶剂重组能的新表达式, 实现了电子转移反应溶剂重组能的数值解, 研究了二氯二氰基苯醌(DDQ)及其阴离子体系DDQ-之间的自交换电子转移反应. 考虑了DDQ与DDQ-分子以平行方式形成受体-给体络合物时的两种构型. 引入线性反应坐标, 计算了该反应在不同溶剂中的溶剂重组能. 基于两态变分模型得到了反应的电子耦合矩阵元. 根据电子转移动力学模型, 计算了该自交换电子转移反应的速率常数.     

电子转移过程的理论——1992年诺贝尔化学奖

1992年10月14日瑞典皇家科学院宣布1992年诺贝尔化学奖授予美国加州理工学院Rudolph A. Marcus教授,以表彰1956—1965年期间他在“电子转移过程理论”方面所做出的重要贡献。电子转移过程可发生于众多的体系之中,如:在溶液中或在胶体中的有机化合物分子;在不同界面如金属/液体界面、半导体/液体以及液体/液体界面的电子转移过程,还有生命体系     

Non-Condon电子转移速率理论与含时波包方法

随着电子转移理论在化学、材料科学、生物医学等领域的广泛应用,人们针对不同体系提出了多种电子转移理论模型。本文主要总结了近年来我们在non-Condon电子转移理论以及含时波包方法等方面的相关工作。首先阐述包含non-Condon效应的电子转移速率理论并用于二噻吩四硫富瓦烯有机半导体迁移率的计算。而后介绍了包含量子相干效应的含时波包方法,并初步用于研究二聚芴分子三三态能量转移过程。另外,本文还阐述了如何采用量子化学计算获得电子转移速率的结构参数。     

生物体系中电子转移机理的理论研究--Ⅲ.含金属螺环化合物的分子内电子转移

用MOPAC-ET程序中AM1方法,计算了金属螺环化合物分子内电子转移的性质及它们与外加电场的相关性,结果表明随着外加电场F的不断增加,反应的势垒则不断降低,当F达到一定值时,反应的活化能为零,此时反应速率最大,计算还表明电子转移矩阵元VAB和重组能λ受外加电场的影响很小,而反应热则与之成正比.     

光合反应中心原初电子转移机理的理论研究

用量子化学密度泛函B3LYP方法在3-21G水平上计算细菌光合反应中心原初电子给体P960和绿色植物PSⅡ光合反应中心原初电子给体P680的电子结构,然后研究轴向配位的组氨酸残基和周围蛋白质环境的影响,最后探讨其原初电子转移机理。计算结果表明：(1)细菌光合作用反应中心原初电子给体P960-h的HOMO主要是由与M分支相连的组成单元上原子的原子轨道组成,而它的LUMO则两个组成单元上原子的原子轨道都有贡献;PSⅡ反应中心中原初电子给体P680的HOMO和LUMO均主要由与D1蛋白相连的组成单元上原子的原子轨道组成。这些计算结果能够从反应中心最核心的部分-原初电子给体的电子结构方面解释Rps.uiridis反应中心和PSⅡ反应中心原初电子转移只沿一个分支进行的的途径选择性。(2)虽然与细菌反应中心原初电子给体超分子P960的两个细菌叶绿素分子形成轴向配位的组氨酸残基His并未参与超分子P960-h的HOMO和LUMO的组成,但是由于其轴向配位,使得P960-h的ELUMO显著地升高到高于辅助细菌叶绿素和去镁细菌叶绿素的相应值,使得原初电子转移反应能够顺利进行。否则原初电子转移反应很难进行。PSⅡ反应中心的情况,与细菌反应中心十分相似。(3)细菌反应中心辅助细菌叶绿素(ABChlb)中的Mg离子与最近的组氨酸残基His中的N原子的距离和原初电子给体P960中的相应的Mg-N的距离相似,因此同样应该考虑此轴向配位的组氨酸残基,此时原初电子转移反应是沿L分支从P960-h经ABChlb到去镁细菌叶绿素(BPheob)的两步电子转移过程。而PSⅡ反应中心的辅助叶绿素不存在His的轴向配位,这应是与细菌反应中心的重要区别之一,此时原初电子转移应是沿Dl分支从P680-h到Pheoa的一步电子转移过程,但同时也不能完全排除从P680-h到AChla到Pheoa的二步电子转移过程。     

构型对芳基桥体分子内电子转移矩阵元影响的理论研究

在HF/6-31G水平上,研究了有机化合物二甲氧基-4-甲苯-四甲苯基桥体-二甲氧基-4-甲苯正离子间的电子转移.用线性反应坐标确定电子转移的过渡态,用两态变分法计算了电子转移矩阵元V_AB,在考虑非平衡态溶剂化效应下,计算了电子转移速率常数.改变桥体与氧化还原中心的二面角,计算了相应的电子转移矩阵元.通过电子结构分析,将电子转移矩阵元分为通过空间的直接耦合和通过键的耦合,提出了将后者进一步分为通过σ键和π键的耦合.得出通过π键的耦合与二面角余弦的平方成正比的结论.     

Theoretical study of electron transfer in uranyl(VI)–uranyl(V) complexes in solution

The rates of the electron self‐exchange between uranyl(VI) and uranyl(V) complexes in solution have been investigated in detail with quantum chemical methods. The calculations have shown that the bond length of U? Oyl is elongated by 0.1 Å when the extra electron is localized on the sites. The diabatic potential surfaces are obtained. The inner reorganization energies are 212.6 and 226.8 kJ mol^?1 for hydroxide and fluoride bridge systems, respectively. The solvent reorganization energies are 28.12 and 31.60 kJ mol^?1 for hydroxide and fluoride bridge systems, respectively. The nuclear frequency factors are 3.17 × 10¹³ and 3.12 × 10¹³ s^?1 for hydroxide and fluoride bridge systems, respectively. The electronic coupling matrix elements are 1.89 and 4.06 kJ mol^?1 for hydroxide and fluoride bridge systems, respectively. The electron‐transfer rates of our calculations are 12.95 and 0.819 M^?1 s^?1 for hydroxide and fluoride bridge systems, respectively. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

生物体系中电子转移机理的研究Ⅱ: 分子间电子转移及 电子供、受体间不同基 团的影响

利用自编程序MOPAC-ET中AM1方法,及KT(Koopman'sTheorem)法,研究了二苯负离子体系的分子间电子转移现象,计算了其电子供、受体在不同距离下的V~A~B及它们之间的相关性,另外,还对两苯环间不同介入基团对电子转移的影响做了初步研究,发现不同的介入基团存在着较大的差异。     

Theoretical study on electron transfer in biological systems (III)

Iritramolwular electron transfer of nlctal-containing spiro π-electron system was studied by AM1 method in the MOPAC-ET program developed by the present group. The results indicated that with the increasing of the outer electric field F, the activation energy of the reaction decreased. When F reaches a certain threshold value, the activation energy barrirr becomcs zero and the rate of reaction achieves the largest value. The results also indicated that electron transfer matrix elements V_AB and reorganization energy λ were not obviously affected by outer electric field while the exothermicity ΔE was directly proportional to it.     

Theoretical investigation of electron transfer transition in tetracyanoethylene-contained organic complexes

In this work, the authors use complete active space self-consistent field method to investigate the photoinduced charge-separated states and the electron transfer transition in complexes ethylene-tetracyanoethylene and tetramethylethylene-tetracyanoethylene. Geometries of isolated tetracyanoethylene, ethylene, and tetramethylethylene have been optimized. The ground state and the low-lying excited states of ethylene and tetracyanoethylene have been optimized. The state energies in the gas phase have been obtained and compared with the experimentally observed values. The torsion barrier of tetracyanoethylene has been investigated through the state energy calculation at different conformations. Attention has been particularly paid to the charge-separated states and the electron transfer transition of complexes. The stacked conformations of the donor-acceptor complexes have been chosen for the optimization of the ground and low-lying excited states. Equilibrium solvation has been considered by means of conductor-like screening model both in water and in dichloromethane. It has been found that the donor and tetracyanoethylene remain neutral in complexes in ground state (1)A(1) and in lowest triplet state (3)B(1), but charge separation appears in excited singlet state (1)B(1). Through the correction of nonequilibrium solvation energy based on the spherical cavity approximation, pi-->pi* electron transfer transition energies have been obtained. Compared with the experimental measurements in dichloromethane, the theoretical results in the same solvent are found higher by about 0.5 eV.     

Competition between superexchange-mediated and sequential electron transfer in a bridged donor-acceptor system

The temperature- and solvent-dependence of photoinduced electron-transfer reactions in a porphyrin-based donor-bridge-acceptor (DBA) system is studied by fluorescence and transient absorption spectroscopy. Two competing processes occur: sequential and direct superexchange-mediated electron transfer. In a weakly polar solvent (2-methyltetrahydrofuran), only direct electron transfer from the excited donor to the appended acceptor is observed, and this process has weak temperature dependence. In polar solvents (butyronitrile and dimethylformamide), both processes are observed and the sequential electron transfer shows strong temperature dependence. In systems where both electron transfer processes are observed, the long-range superexchange-mediated process is more than two times faster than the sequential process, even though the donor-acceptor distance is significantly larger in the former case.     

肽链体系中的长程电子转移: 酪氨酸与色氨酸间电子转移的理论研究

用电子转移的半经典模型和量子化学半经验方法对色氨酸-酪氨酸二肽体系进行电子转移动力学参数计算.用AM1方法分别优化给体、受体和桥体几何构型,用线性反应坐标的构造了给体和受体分子间电子转移的双势阱,得到两透热势能面交叉处的反应坐标为R=(约等于)0.10,并确定了反应的内重组能及反应热.对色氨酰酪氨酸和酪氨酰色氨酸体系进行闭壳层HF自洽场计算,按Koopmans定理计算体系分子轨道分裂能值A(三角形),在R约为0处发现了A(三角形)的极小值,从而获得色氨酰酪氨酸及酪氨酰色氨酸体系分子内电子转移的电子转移矩阵元V~D~A分别为0.96kJ.mol^-^1和0.87kJ.mol^-^1.采用Marcus双球模型估算反应的溶剂重组能为64.60kJ.mol^-^1。     

Quantum electron transfer processes induced by thermo-coherent state

When the reactant surface is not in a thermal equilibrium, but in a thermo-coherent state we have derived the rate and discussed about the quantum features of the rate. In the limit of very low and very high temperature the expressions are derived analytically and compared with the case of thermal distribution. We have investigated the dependence of temperature on the rate due to displacement, distortion of the harmonic potential energy surfaces of the reactant and product manifold.     

Theoretical study of electric field‐induced intramolecular electron transfer in donor–acceptor pairs via the rigid space and their suitability as molecular electronic devices

The geometries of two reaction systems have been optimized under the constraint of C_2ν symmetry, using the UHF/6‐31G method. The potential energy surfaces (PES) of the two systems in different external electric field have been constructed using a linear reaction coordinate. It is concluded that the reorganization energies and electron transfer matrix elements for both systems are almost independent of the external electric field. However, the standard Gibbs energy difference changes remarkably with the change of the external electric field. Hence, the applied electric field leads to the variation of rate constant of electron transfer reaction. The threshold field, where the electron transfer becomes barrier free, is obtained to be 0.0015 a.u. for the anion system 1, and 0.00097 a.u. for the anion system 2. The threshold field for modified system 1, in which the hydrogen atoms linking to benzene rings are replaced by fluorine atom, is 0.0018 a.u. The calculations show that the best way to adjust the threshold field is to adjust the dipole moment of the reaction system by changing the length of the bridge. As the rate constant in field‐free case is taken into account, neither reaction systems could be used as molecular electronic device. But if the bridge consists of three or four HCTDs, the rate constant and threshold field will satisfy the practical demand. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006