密度泛函理论研究吲哚并咔唑同分异构体结构,芳香性和光谱性质

在B3LPY/6-31G(d, p)基组水平上,利用密度泛函理论(DFT)优化了吲哚并咔唑五种同分异构体的几何和电子结构.基于这五种同分异构体的几何结构下,其吸收和发射光谱的研究使用相同的基组水平并采用极化连续介质模型(PCM)下用含时密度泛函理论(TD-DFT)计算.由于三种近似线性分子(吲哚并2,3-a]咔唑、吲哚并2,3-b]咔唑和吲哚并3,2-b]咔唑)的电荷转移跃迁的振荡强度较大,这些异构体的发射光谱存在明显差异;基于吲哚并2,3-c]咔唑和吲哚并3,2-a]咔唑的构型特征,这两种同分异构体的发射谱具有高能量.比较计算结果表明,吲哚并2,3-b]咔唑在这些分子中的振荡强度最大.这是因为当吲哚并咔唑的五种同分异构体的结构从基态变为激发态时,这些分子的分子轨道(MO)能级不同.由计算结果还得出,这五个分子适用于P型传输材料,并且每个分子的三个苯环均具有共轭效应.

Density Functional Theory Study on Structure, Aromaticity and Optical Properties in Indolocarbazole Isomers

The geometrical and electronic structure of indolocarbazole isomers are optimized by using density functional theory(B3LPY) at the 6-31G(d,p) level. Based on their geometric structures, the absorption and emission spectra were calculated using time-dependent DFT(TD-DFT) with the same basis set and employing the polarizable continuum medium model(PCM). There are obvious differences in the emission spectra of these isomers as the oscillator strength of the charge transfer transition for three approximate linear molecules (indolo2,3-a]carbazole, indolo2,3-b]carbazole and indolo3,2-b]carbazole) are bigger; indolo2,3-c]carbazole and indolo3,2-a]carbazole maintain high-energy emission based on the configurational characteristics. The comparison results, the oscillator strength of indolo2,3-b]carbazole in these molecules is the largest. This is because the structures change from ground state to the excited state and the molecular orbital(MO) energy levels of these molecules are different. The five molecules are right for P-type transport materials, and the three benzene rings for every molecule have conjugated effect.