| Since electroluminescent phenomenon of organic polymers were reported by Cambridge University on Nature in 1990,the dissoluble polymers attract more and more attentions all over the world due to many merits such as they are easy to be processed, flexible, membranous and their energy gaps can be adjusted by chemical technologies. Poly-phenylenevinylene (PPV) is a good electroluminescent material. Oligomer, as the model compound of PPV, is very important to study the characteristics of PPV by theoretical calculation. At the same time, oligomer itself is also used in many of fields as electroluminescent material. 1,4-distyryl benzene (DSB) is the oligomer of PPV that is researched the most extensively. It is a blue light-emitting material and it has high fluorescent quantum efficiency in solution. In solid, however, the fluorescence quantum efficiency of DSB is very low because there is very strong π-πstacking effect among the conjugated molecules, which limits its application in the light-emitting diodes. In order to solve this problem, our group designed and synthesized the oligomers of PPV with biphenyl bridge: 2,5,2',5'-tetrastyrylbiphenyl (TSB) and 2,5,2',5',2'',5''-hexa styryl-[1,1';4',1'']-terphenyl (HSTP). They have tortuose structures and their fluorescent quantum efficiency is obviously increased. The 3D structures of TSB and HSTP, especially the relationship between the effects of π-πstacking and the 3D structures, are the main question to discuss. To make them clear is important for us to improve the material system. However, it is difficult to know the 3D structure of TSB and HSTP by forming single crystal because their tortuose structures are difficult to crystalize. Fortunately, theoretical chemistry affords a very good method to study the structure of molecule and their characteristics, which is extensively applied to the study of the photoelectronic materials. In this dissertation, we have optimized TSB and HSTP by using DFT/B3LYP method with Gaussian 98 software and gained the most rational geometry structure of ground state. We find that biphenyl bond makes a cross angle over 60°between two chains of DSB and tortuose derivative in the same chain. The optimized geometry structures of ground state are approved by experimentaldata. We think that the cross and tortuose structure is likely to be the important factor that increases the fluorescence quantum efficiency of the solid film because of attenuating π-πstacking. In addition, it is an effective way to change the frontier molecular orbital energy level and HOMO-LUMO energy gap when we join some kinds of different substitute groups at the end of DSB chains. However, just because TSB and HSTP have biggish tortuosity, it can decrease the effective conjugate length and rigidity at emitting center in each DSB chains. In addition, biphenyl single bond permit two DSB chains to rotate, which increase the probability of the non-radiation in solution. So fluorescent quantum efficiency is depressed and the application is limited. For the sake of improving the material system, we analyze the data of experiment and the results of computation and summarize the merits and demerits of these molecules, then we design three kinds of molecules including oligomers of PPV: 3',6'-diphenyl-2,5,2',5', 2'',5''-hexastyryl-[1,1';4',1'']terphenyl (DPHSTP), 1,2-bis-(2,5-di styrylphenyl)ethyne (BDE) and 1,4-distyryl-2,5-bis-(2-(2,5-distyrylphenyl)ethynyl)benzene (DBEB). We propose the synthesis route for them and verify that it was realizable. We have fully optimized their structures by using DFT/B3LYP/6-31G method and gained the best rational geometry structure of ground state and electronic energy level. Then the absorption spectra data are calculated at ZINDO and TD-DFT level of theory. The results indicate that DPHSTP is a plane structure in each DSB chain and...
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