【作者】 许海；

【导师】 马於光； 杨兵；

【作者基本信息】 吉林大学 ， 物理化学， 2005， 硕士

【摘要】 聚对苯撑乙烯(PPV)是一种很好的电致发光材料。PPV 的模型化合物——齐聚物的性质对研究PPV 的性质具有很重要的意义。同时,齐聚物本身也可以作为很好的电致发光材料应用于众多领域。PPV 的三聚体(DSB)是研究最广泛的PPV 齐聚物,它是一种蓝色发光材料,在溶液有较高的荧光量子效率,但由于其平面结构使固体中分子间具有很强的π-π堆积作用导致固体的发光效率很低,影响了发光器件的应用。为了解决这个问题,我们实验组设计合成了两种联苯桥联的PPV 齐聚物,具有扭曲的空间构型,明显地提高了固体膜的发光效率。联苯桥联的PPV 齐聚物分子的空间结构,是一个重要的课题,对于进一步完善材料体系具有重要的意义。然而,由于这类分子体系的扭曲空间构型使分子间的作用力减弱,难以形成高质量的单晶来确认结构,致使我们对其空间构型尚不是很明确。本论文从理论化学角度计算并分析了此类分子的基态构型、电子结构和吸收光谱的特性,具体工作主要包括以下两方面内容: (1)通过量化计算确定了两种典型的联苯桥联的PPV齐聚物的基态分子的几何构型和电子能级,并用ZINDO、TD-DFT方法分别计算其吸收光谱,分析了不同类型的端位取代基对前线分子轨道能量和能隙的影响,解释了PPV系列齐聚物在溶液和固体中发光效率成反向变化的原因。(2)在分析和总结了实验中已合成的PPV 齐聚物光电性质及其优缺点的基础上,我们设计了三种含有PPV 齐聚物结构的分子。通过计算,确定了各自可能稳定存在的基态几何构型、电子能级和吸收光谱。发现它们对现有材料的光电性质在一定程度上起到了扬长避短的作用,这对我们今后的理论和实验工作具有一定的指导意义。更多还原

【Abstract】 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更多还原