Complexes [au (c (?)-c 4-of Lno <sub> 2 </ Sub>) (pph <sub> 3 </ Sub>), L =-c <sub> 6 </ Sub> H <sub> 4 </ Sub>-c <sub> 5 </ Sub> The H <sub> 3 </ Sub> N,-c <sub> 4 </ Sub>

New materials with desirable nonlinear optical (NLO) properties have been the subject of intense interest recently. Amongst this array of materials are gold-containing compounds with significant second and third NLO properties, especially the binuclear and mononuclear compounds coordinated by phosphorus, which have been the focus of recent research.Based on perturbation theory, the sum-over-states method can take into consideration of the frequency of outfield and perform electron correlation energy correction, thus it can reveal the excited states properties on the NLO response and it has been widely used in the calculation of NLO. However most of the SOS calculations are based on the semi-empirical methods, Herein, The relation between NLO properties and geometric structures of gold complexes [Au(C=C-4-LNO2) (PPh3), L=-C6H4, -C5H3N, -C4H2N2] and [Ph3P-Au-Au-PPh3] have been detailed studied using time-dependent density functional (TDDFT) theory and sum-over-states (SOS) method.In the second part, several typical small molecules and furan as well as its homologues are considered validating the reliability and accuracy of TD-SOS. The results also have been compared with that obtained with CCSD(T), TDHF and Finite Field (FF) methods. It shows that TDDFT-SOS is superior to TDHF and FF methods and close to CCSD(T). So we can deem it as a satisfying method in the NLO properties calculation.In the third part, the calculations reveal that there is an increase in ft value with the decreased aromaticity of the replacement of a nitrophenylacetylide by a nitropyridylacetylide ligand for the model complexes. The calculation results presented a good consistent with the HRS measurements at 1064nm. It provides an opportunity of designing organometallic complexes with large # values.In the forth part, partial electronic charge has been localized on the two Au atoms by the Au-Au interaction, which connected the "D-A" and "A-D" molecular moieties to the "D-A-A-D" molecule, and extended thedelocalized scopes of electronic charge on the molecular framework, indicating that the Au-Au interaction plays an important role in NLO properties of the model systems; There is a close relationship between the y value and change of basis sets. The ym value is increased with larger valence electronic basis sets. In [M2(PH3)2, M=Cu, Ag, Au], the change rules of YOV value (YAg Yci^ YAU) agree with that of MLCT electronic charge transfer (AQAg->p>AQcu->p >AQAu->p)- The calculated dispersion behavior shows that the change rules of Y(-3w;to,to,co) value also agree with that of MLCT electronic charge transfer (AQAg->p>AQcu-籶 >AQAu_>p).