Theoretical Study Of The Nolinear Optical Properties Of Gold Complexes

Functional material has been widely applied in many fileds due to its characteristics and function such as electricity, light, sound, magnetism and heat etc. In future, how to find and design novel functional material is the foundation of the development of the advanced scientific technology. Thus, the achievement in designing and developing functional material becomes hot problem in scientific research. As one of the most important parts of the design of functional materials, the design of nonlinear optical materials has also been focused on by physicist, chemist and material scientist all the time. In the past few years, both experimental and theoretical studies in nonlinear optical field have made big progress, especially in theory. In general experimental condiation, there are weakly intermolecular interaction and solvent effects. These weak interaction and solvent effects might have certain effects on the nonlinear optical properties. Thus, it is not possible to directly compare a macroscopic quantity with a microscopic one or convert each other. Comparison of calculating results with experimental ones is very useful to understand the contribution from these effects. There is also certain instructive meaning in establishing the structure-property relationship,In this thesis, nonlinear optical properties of a series of novel gold complexes were studied by using TDDFT-SOS and FF methods, especially in the effect of M...M attraction on nonlinear optical properties. Gold(III) alkyl complexes, [(But2Im)AuX] (X=halogen) complexes, gold(I) N-heterocyclic carbene and carbazolate complexes and HC[PH2MC1]3 (M=Au, Ag and Cu) were optimized by DFT method. Based on the optimized structures, electronic transiton properties, M...M interaction and NLO properties of these complexes are systematically studied and relationships between structure and property are established. We want to find the main factors in enhancing the nonlinear optical properties. Our investigations will focuse on the four aspects:(1). The second-order nonlinear optical properties of gold(III) alkyl complexes are calculated by using time-dependent density-functional theory (TDDFT) combined with the sum-overstates (SOS) method. The results show that these complexes possess larger molecular second-order polarizabilities compared with the organic smaller compounds and typical organometallic complexes. The analysis suggests that the second-order nonlinear optical response was determined by charge transfer along the z-axis direction. Moreover, different ancillary ligands can substantially adjust the second-order nonlinear optical response. Thus, it can be concluded that these complexes will be hopeful candidates for the second-order nonlinear optical materials from the standpoint of high transparency, relatively largeβvalues and small dispersion behaviors. (2). The dipole polarizabilities and second-order polarizabilities of recently synthesizedr 1,3-di-ter-butylimidazol-2-ylidine gold complexes [(Bu’2lm)AuX] (X=halogen) were investigated by using finite-field (FF) method. The effects of different methods and functionals on dipole moment, polarizability, and second-order polarizabilty have been studied. The analysis of frontier MOs shows that the charge transfer from the halogen atom to the carbene ligand makes dominant contributions to the NLO response. The metal atom in the studied complexes acts as an intermediary between an electron-donor and an electron-acceptor moiety. The dynamic second-order NLO response shows that all the studied complexes have small disperse behaviors and are applicable to frequency conversion optical materials. All the complexes have high transparency in the visible area. In view of the merit of [(Bu2tIm)AuX] (X=halogen), they can become an excellent kind of material in the second-order NLO field.3. The M...M attraction and nonlinear optical properties of gold(I) N-heterocyclic carbene and carbazolate complexes have been systematically investigated. The results show that MP2 and coB97X can be used to describe the equilibrium distances and M...M attraction energy, In the monomer, fiz value is the largest components;βx value is the smallest components. However, the behavior of the dimer is different from that of the monomer. In the dimer,βz value andβy value are almost equal,βx value is smaller than that of fiz value andβy, but much larger thanβx value in the monomer, fix corresponds to the direction of M...M attraction, which means that M...M attraction has certain effect on the nonlinear optical properties. Comparison between the transition dipole moments between monomer and dimer, M...M attraction has also contribution to the nonlinear optical properties4. The structures and NLO properties of H2C[PH2MCl]2 and HC[PH2MCl]3 (M=Au, Ag and Cu) have been investigated by MP2 theory. The calculation results show that Au...Au interaction is larger than that of Ag...Ag and Cu...Cu interaction. Moreover, the system containing Au...Au interaction shows larger polarizability and first-order hyperpolarizability due to its larger charge transfer. The componentβz suggests that stronger Au... Au interaction contributes to NLO properties. Therefore, H2C[PH2AuCl]2 and HC[PH2AuCl]3 may be the excellent second order NLO material candidate.