共轭性取代对咔唑类衍生物结构和光谱性质影响的理论研究

The effect of conjugation on the structure and electronic spectrum of carbazole derivatives

用密度泛函理论（DFT）和含时密度泛函理论（TD-DFT）对咔唑的6种共轭基团取代衍生物的电子结构和吸收光谱性质进行了比较研究。对衍生物的基态分子结构运用B3LYP/6-31G（d）水平进行全优化,分析了电荷的分布和前线分子轨道等性质。结果表明,与母体咔唑相比,各衍生物均形成了分子内氢键,共轭体系的π键成分增大,能级差减小,激发能降低,分子的最大吸收波长向长波方向移动,即发生红移。前线分子轨道分析表明该类化合物吸收光谱主要对应分子中的HOMO→LUMO电子跃迁,且为π-π~＊跃迁。共轭性基团的引入扩大了分子结构的共轭范围,增强了分子内电子的转移,改善了咔唑类化合物的光电性能。本文为新型含咔唑基团的光电功能材料的设计合成提供了理论参考。

The electronic structures and absorption spectral properties of six carbazole derivatives were investigated based on density functional theory （DFT） and time-dependent density functional theory （TD-DFT）. The geometrical structures of six compounds were obtained at the B3LYP/6-31G（d） level of theory, and then the charge distribution and the frontier molecular orbital property were discussed in detail. The calculation results showed that the absorption bands of the conjugated systems suffer bathochromic shift with the K-conjugated bonds increasing, the energy level difference decreasing, and the excitation energy reducing correspondingly. In addition, the frontier molecular orbital analysis indicated that maximum absorption bands mainly originate from the HOMO→LUMO electronic transitions, i.e. π-π＊. The introduction of the conjugate group into carbazole molecule could expand the conjugation effect, enhance the intramolecular electron transfer, and improve the photoelectric property of carbazoles. This work would provide theoretical reference for the design synthesis of the new carbazole-based photoelectric functional materials.