芴与苯并硒化二唑共聚物的电子结构和光谱性质的理论研究

Theoretical Investigation of Electronic Structures and Optical Properties of Conjugated Polymers Derived from Fluorene and Benzoselenadiazole

用密度泛函B3LYP方法对低聚体（DEF-BSeD）n（n=1～4）[其中9,9二乙基芴（DEF）单元与苯并硒化二唑（BSeD）单元的摩尔比分别为1∶1和2∶1]进行全优化,计算电离能（PI）、电子亲和势（EA）和能隙（ΔH-L）,在基态结构的基础上用TD-DFT和ZINDO方法计算激发能和电子吸收光谱,并利用外推法得到高聚物的相应性质.从外推结果看出,随着聚合物中BSeD比例的增大,聚合物的最低单激发能呈减小的趋势,最大电子吸收光谱红移.用CIS方法优化得到单体的S1激发态结构,计算结果表明,激发态的结构更趋近于平面构型.

The ground states of poly（9,9-diethylfluorene-co-alt-benzoselenadiazole） were full optimized with DFF at B3LYP/3-21 G^＊ level, in which the comonomer molar ratios of 9,9-diethylfluorene（DEF） and benzoselenadiazole（BSeD） are 1：1 and 2： 1. TDDFT and ZINDO calculations of the lowest excitation energies and absorption wavelengths were performed at the optimized geometries of the ground states. Band gaps of the corresponding polymers were obtained by extrapolating HOMO-LUMO gaps and the lowest excitation energies as well as the maximal absorption wavelengths of the polymers to the infinite chain length. By the extrapolation results, the bond gaps are becoming lower with increasing the concentration of BSeD, while the maximal absorption wavelengths are red-shifted. The excited geometry is optimized by ab initio CIS/3-21 G^＊ and the emission spectra was computed based on the excited geometry. By the calculation results, the excited geometry was more planar.