【摘要】 用密度泛函方法对联苯桥联的PPV齐聚物(TSB)的反式结构进行全优化,得到基态分子的最优几何构型和电子能级,并用ZINDO和TDDFT方法分别计算其吸收光谱,分析了不同类型的端位取代基团对前线分子轨道能量和能隙的影响.结果表明,联苯桥联后的PPV齐聚物在结构上形成了链间交叉链内扭曲的构象,这种交叉扭曲的构象降低了分子的对称性,减弱了共轭分子在固体中的ππ堆积作用,这可能是减少荧光猝灭效应,提高固体发光器件效率的重要原因.更多还原

【Abstract】 We fully optimized the %trans%-structures of PPV oligomer with biphenyl bridge using DFT/B3LYP method with Gaussian 98 software and gained the most rational geometry structure of ground state and electronic energy level. Then the absorption spectra data are calculated at ZINDO and TD-DFT levels of theory. We also analyzed the factors that different substituent groups connecting to the end of molecules impacted the frontier molecular orbitals and the energy gap. The results indicate that the PPV oligomer with biphenyl bridge is a cross form between two chains and tortuose derivative in the same chain. It reduces molecular symmetry and weakens %π-π% stacking effect among conjugated molecules in solid. This is perhaps the important factor that light-emitting diodes can increase fluorescence quantum efficiency.更多还原