【作者】 潘清江；

【导师】 张红星；

【作者基本信息】 吉林大学 ， 物理化学， 2005， 博士

【摘要】 过渡金属配合物的电子吸收和发射是极其复杂的微观过程,涉及到基态与激发态的电子结构性质、金属间弱相互作用、相对论效应等量子理论的基础问题,所以该类配合物发光性质的理论研究不仅对无机新型光学材料的探索和设计具有重要指导意义,而且本身就是极其重要的理论课题。本文采用理论方法对一系列d⁸和d¹⁰配合物进行了研究,主要成果如下: 1. 对十二个双核Au（I）磷硫配合物的激发态研究揭示了随着硫醚、磷和硫醇盐配体的更替,配合物的发光性质从MC→MC/MMLCT→MLCT 递变。不同电荷转移特征的发射导致材料发光过程中发光波长、发光寿命、量子产率等性质的显著不同,因此这一规律性对实验工作具有重要指导意义。2. 通过d⁸和d¹⁰系列配合物在MP2 水平的计算,得到了闭壳层d⁸–d⁸和d¹⁰–d¹⁰弱相互吸引作用源于:配体的配位一定程度上改变了金属的纯闭壳层电子结构;电子相关对金属间弱相互吸引起到了重要作用;重金属的相对论效应明显增加金属间弱吸引强度。金属间弱吸引作用使配合物以MC 和MMLCT 跃迁为特征的激发态几何结构和电子结构显著不同于基态。其相互作用在激发态明显加强,甚至出现很强的金属-金属键,导致双核配合物的发射波长与单核配合物相比发生红移。3. 应用超分子模型和自洽反应场模型研究了溶剂化效应对d⁸ 和d¹⁰ 配合物发光性质的影响,对固态行为采用二聚模型和平衡离子校正,得到了配合物在气态-固体-溶液的递变过程中发光变化的规律性。4. 有机共轭体系可能有好的荧光发光性质,但不能作为磷光发光材料。通过研究以有机共轭体系为配体的Au（I）配合物基态和激发态的电子结构,表明在电子发射过程中产生以MC 跃迁、MMLCT 和有机配体内的ILCT 为特性的各种发光机制。因此,金属与有机配体之间相互修饰。重金属的相对论效应使旋-轨耦合条件成立,有机共轭体系好的荧光发光性质可转变为好的磷光发光性质。金属与有机配体之间电荷转移使得发光性质多样化。因此,过渡金属有机共轭体系配合物发光材料兼具有机和无机材料的双重特性!更多还原

【Abstract】 Because of its characteristics and function such as electricity, light, sound, magnetism and heat etc., functional material has been paid most attention to in the last five decades. The achievement in designing and developing functional material not only has greatly promoted the revolution of scientific technology in the late 20th century, but also will act as the foundation of the development of the advanced scientific technology in future. As one of the most important parts of the design of functional materials, the design of optical materials has also been focused on by physicist, chemist and material scientist all the time. Recently, a great deal of experimental work on the electronic absorption and emission of transition metal complexes has been performed to seek inorganic optical material that exhibits intensive luminescence in the visible region. The absorption and emission of transition metal complexes usually are related to the charge transfer between d orbitals of metal and s/p orbitals of metal or ligand. Because such an electronic absorption in the ultraviolet region usually conduct the corresponding emission in the visible region, transition metal complexes are one of the most excellent candidates to serve as visible-region optical material. The electronic absorption and emission of molecules are complicated microscopic processes between the ground-and excited-state transitions. With the development of quantum chemistry and computational technique, especially the successful application of density functional method, the electronic structures and properties of molecules in the ground state have been fully understood in theory and widely applied in chemistry. However, the studies on the excited-state properties still remain infant and excited states themselves are related to many photoelectric phenomena in the modern chemistry and physics. Therefore, quantum chemistry related to the electronic excited states should be one of the most major research directions in the future. Presently, it is a challenge to apply quantum theory to investigate luminescent properties of transition metal complexes, but such a kind of research is of theoretical and practical significance. Transition metal atoms have various electronic structures and bonding characters and many ligands have been synthesized in experiments, resulting in the occurrence of thousands of transition metal complexes. It is very difficult to fully understand the properties of such abundant complexes. So, it is an ideal start point to investigate a kind or several kinds of complexes with simple coordination geometry. So far, a number of d8 and d10 complexes have been synthesized with well-known structures. It was found that many d8 and d10 complexes exhibit intensive luminescence and can be applied in the optical materials; their long lifetime of phosphoresce makes them be used as photosensitizer, photochemical catalysis and optical sensor; their interaction with DNA leads to the application in the molecular pharmacy. The experimental studies show potential applications of transition metal complexes in many fields. Lack of theoretical support, insight into the luminescent process and microscopic mechanism is only empirical, which results in experimental deviation from reality. Thus, systematic studies on the d8 and d10 complexes in theory to rationalize and predict experimental phenomena are of practical significance. The electronic excited states of molecules have higher energy and unsteady characteristics, which easily emit the energy to recur the steady ground state in a short time. So it is difficult for experiment to obtain reliable information about the excited states of molecules. Theoretical chemists attempt various electronic structure theories of excited states to seek the method that can accurately predict excited-state electronic structures and be applied in the calculations of relatively large molecules without consuming excess computational resources. So far, CIS (Single excitation configuration interaction) and TD-DFT (Time-dependent density functional theory) methods have been widely used to treat the electronic excited states of large molecular systems. It has been established that the solvents affect the luminescence of complexes. Many theoretical methods were employed to treat properties of complexes in solution. The first strategy puts the attention on the microscopic interactions of the solute with a limited number of solvent molecules; the whole system (the“supermolecule”) is studied with quantum mechanical methods usually employed for single molecules, and the effects of specific solute-solvent interactions are brought in evidence. An increasing number of solvent molecules can be added to this model, thus gaining supplementary (and detailed) information about solvent effects. The second strategy tries to directly introduce statistically averaged information on the solvent effect by replacing the microscopic description of the solvent with a macroscopic continuum medium with suitable properties (dielectric constant, thermal expansion coefficient etc.). Recently, QM/MM (Quantum mechanical and molecular mechanical) method has been developed to account for the solvent effects. The advanced technique applied in experiments greatly promotes the development of modern computational chemistry. On one hand, the comparison between calculation and experiment can test the reliability and accuracy of electronic structure theory, showing the dependence of theory on experiment; on the other hand, to develop the electronic structure theory is to support and/or supplement the known experimental results, and further to predict the potential results, indicative of theoretical forward looking and independence. In the paper, combining the benefits of various quantum chemical computational methods and considering the solvent effects, we systematically studied luminescent properties, ground-and excited-state electronic structures, and metal-metal interaction of d8 and d10 complexes and obtained the following main results: 1. The MP2 (Second-order M?ller-Plesset perturbation) and CIS methods were employed to fully optimize the ground-and excited-state structures of binuclear Au(I) complexes with eight-membered ring skeleton, respectively. Such complexes contain any one or two among thioether, phosphine and thiolate ligands and give 12 binuclear Au(I) complexes in all. It was shown that positively bivalent complexes (including 5 model complexes) give rise to the lowest-energy σ(s)→σ*(d) (Metal-centered, MC) phosphorescent emission, which reflects the luminescent nature of real complexes. The Au–Au distance in the 3[σ*(d)σ(s)] excited state is much shorter than that in the corresponding ground state. CIS calculations revealed that the coordination from acetonitrile to Au(I) atom results in a large red shift of fluid emission wavelength relative to the gas phase. Our studies indicated that the chair and boat conformations adopted by the Au(I) complexes slightly affect their Au–Au aurophilicity and excited-state properties. However, the introduction of Me substitutent into phosphor and/or sulfur atoms (substitutent effect) leads to the blue shift of emission wavelength but does notchange the excited-state character, suggesting that the approximation of hydrogen in place of heavy substitutent is feasible in the work. In addition, the unrestricted MP2 (UMP2) calculations on the 3[σ*(d)σ(s)] excited states of such complexes confirm the CIS optimized geometry and calculated emission energy. It was found that thiolate ligand plays a dominant role in the emissive transition of neutral Au(I) complexes (including 6 Au(I) complexes). Their phosphorescent emissions were attributed to metal-metal to ligand charge transfer (MMLCT) transitions. The promotion of electrons into the σ(s/p) bonding orbital between the two Au atoms results in the enhancement of Au–Au interaction in the excited state with respect to in the ground state. Negatively bivalent complex displays metal to ligand charge transfer (MLCT) phosphorescence. The Au–Au separation in the excited state is much longer than that in the ground state, indicative of no metal-metal interaction. Summarizing studies on the 12 Au(I) complexes, we come to their luminescent regularity: with the interchange of thioether, phosphine and thiolate lignads, the luminescent properties vary from MC to MC and/or MMLCT to MLCT. The emissions with different charge transfer characteristics result in significant differences of emission wavelength, lifetime and quantum yield in the luminescent progress. Thus, such a luminescent regularity is very important in guiding the experimental work. 2. The structures of [Au2(PH3)2(i-mnt)] (2) and [Au2(PH2CH2PH2)(i-mnt)] (3) (i-mnt = i-malononitriledithiolate) in the ground and excited states were studied in detail by the ab initio methods; The IPCM (Isodensity Polarized Continuum Model) in the SCRF (Self-Consistent Reaction Field) method was applied to account for the solvent effect; We used the dimerized model to simulate the behaviors of 2 and 3 in the solid state. UMP2 calculations on such complexes confirm CIS results. The frequency calculations on the Au(I) complexes in the ground and triplet excited states at the MP2 level demonstrated that the Au–Au bonding character changes greatly upon excitation. The comparison between open-ring 2 and closed-ring 3 revealed that the Au–Au interaction is attractive in nature and not imposed by the steric bulky bridging ligand. The studies on the electronic structures of these complexes showed that their luminescence ranges from organic i-mnt ligand ILCT (Intraligand charge transfer) to MLCT to MC transitions. The introduction of organic ligand highly diversifies the luminescent properties of the Au(I) complexes. 3. Followed studying the aurophilicity and excited-state properties of binuclear Au(I) complexes in detail, the calculations were extended to other更多还原