【作者】 易海波；

【导师】 李象远；

【作者基本信息】 四川大学 ， 物理化学， 2003， 博士

【摘要】 光诱导电子转移理论研究在光化学反应对于设计、光合作用机制研究、太阳能利用和分子开关和分子器的开发件等方面具有重要的意义。本文通过理论计算揭示共轭体系的分子间光诱导电子转移的机理，用连续介质模型估计电荷转移(CT)跃迁过程的溶剂化能，探讨光诱导电子转移的动力学问题。 考虑电子相关的MP2方法研究了电子给体和受体间的相互作用，探讨了计算电子给体和受体分子间相互作用时存在的基组重叠误差问题。本文采用单激发组态相互作用(CIS)方法，全活化空间自洽场(CASSCF)方法和含时密度泛函理论(TDDFT)研究了电子给体四氰基乙烯(TCE)与一些烯烃和芳烃化合物间的光诱导电子转移过程。以上三种方法的计算结果的比较表明，在研究的体系的低激发态时，CIS方法仍是一种合适的选择。采用自然键轨道电荷分布分析和分子轨道分析等方法，研究了基态和激发态的电荷分布变化以及电子跃迁的性质。理论计算结果的分析显示电子给受体(EDA)配合物电荷转移(CT)吸收光谱是由电子给体的前线π轨道和受体的前线π~*轨道轨道间的跃迁引起的。理论计算揭示了EDA配合物的CT激发态产生的机制，一种机制是可以由EDA配合物的直接激发得到CT激发态，另一种由较高局域激发(LE)态的衰变得到的CT激发态。通过定性分子轨道理论探讨了CT吸收光谱强度与轨道相互作用之间的关系，并从理论计算的角度揭示了实验中9,10-二氰基蒽与杜烯(DCA-DUR)体系的CT吸收光谱很难发现的原因。本文用CIS方法得到离子对的几何结构，并探讨了其气相CT发射光谱。 结合SCRF/Onsager计算方法和非平衡溶剂化处理，研究了EDA配合物的CT吸收光谱和离子对的CT发射光谱的溶剂效应，并进一步讨论了第一溶剂化层对CT吸收光谱的影响。与实验结果的相比，连续介质模型能较好地估计CT跃迁过程的溶剂化能，溶质与溶剂间的弱氢键作用对CT吸收光谱的影响并不大。本文利用推广的Mulliken-Hush(GMH)方法计算了DCA-DUR，四氰基乙烯与苊撑以及四氰基乙烯与四甲基乙烯等体系的电子转移偶合矩阵元，考察了溶剂效应对电子转移偶合矩阵元的影响，根据Golden规则探讨了电子复合的返回电子转移的跃迁几率以及电子复合的几种可能途径。更多还原

【Abstract】 Photoinduced electron transfer (ET) is one of the most pivotal processes in photosynthesis, organic reactions and optoelectronic devices. In this work, we intended to study the mechanism of photoinduced intermolecular ET reaction, including the estimation of the solvation energy in charge transfer (CT) transitions,and investigation of the kinetics of photoinduced ET.The interaction energy between electron donor and acceptor was investigated using second order M011er-PIesset method, and the counterpoise method was adopted to consider the correction of basis set superposition error for the interaction energy. The electronically excited states of electron donor-acceptor (EDA) complexes and ion pair complexes were investigated by means of several popular quantum chemical methods, the configuration interaction singles (CIS), the complete active space self-consistent field (CASSCF) method, and the time-dependent density functional (TDDFT) calculation. Comparison of the CIS results with those by CASSCF and TDDFT shows that CIS method is a proper choice in calculating low-lying charge-balanced excited state and excited charge transfer (CT) states in large π-conjugated systems. Applying the natural bond orbital population analysis and molecular orbital analysis, we investigated the electron population of ground and excited states and the transition properties. Theoretical calculations indicated that the photoexcitation of charge-balanced EDA complexes may lead to CT absorptions, which arise from π-π* excitations. Some theoretical evidences were provided for the experimental observations so that no CT absorption was not observed in DCA-DUR complex. Our results revealed that CT state of EDA complex can be formed directly through the photoexcitation of EDA complex, whereas the CT state can be produced by the decay of locally excited (LE) state. The geometries of ion pair complexes were optimized using CIS method in this work.Invoking the continuum model, we investigated the solvent effect on CTabsorption, local excitation and CT emission in polar solvents. Equilibrium solvation energies of the ground and excited states of EDA complex were calculated by using the self-consistent reaction field (SCRF) method. Based on the treatment of non-equilibrium theory, solvation energy corrections for the vertical transitions were evaluated. The solvation shifts of CT absorption and CT emission in the polar solvent, compared with those in the gas phase, were estimated. Explicit hydrogen bonding effect of solvent molecules on the CT absorptions was considered in this work, using supermolecular model.According to the generalized Mulliken-Hush (GMH) model, electronic coupling matrix elements in the decay processes of LE states and those in the charge recombination (CR) processes of contact ion pair (CIP) complex were evaluated. Based on the Golden rule, discussions on the probabilities of different CR processes of CIP complex were made. The solvent effect on the CR processes of CIP complex was considered as well.更多还原