利用密度泛函理论研究α-联噻吩体系H(C_4H_2S)_nH的结构和电子光谱

Density functional theory study of structure and electronic spectra ofα-oligothiophenes H(C_4H_2S)_n H

应用密度泛函理论，在B3I，YP／6—31G（d）和CAM—B3LYP／6—31G（d）水平上优化了α-联噻吩体系H（C4H2S）nH（n=2～13）的基态几何构型；与此同时，利用TD-B3LYP方法计算了H（C4H2S）nH的吸收光谱，得到了其垂直激发能和体系大小”的解析表达式；并采用TI〉CAMB3LYP方法研究了其发射光谱．研究表明，H（C4H2s）nH的基态结构呈现三种构型：螺旋上升型、环型和稍有弯曲的带状结构；其中前两种构型是顺式结构，最后一种构型是反式结构；环型结构具有C2对称性，其他两种结构具有C1对称性．此外，其吸收光谱和发射光谱计篦佰与宴马令佰吻合．

Density functional theory was adopted to optimize the ground state geometries of a- oligothiophenes H（C4H2S）,,H （n = 2--13） with B3LYP and CAM-B3LYP methods of 6-31G （d） basis set. In the meantime, the absorption spectra of H（C4 H2S）nH were calculated with TD B3LYP method, and their analytic expressions of vertical transition energies versus size n were derived therewith. Moreover, the emission spectra of H（C4 H2S）nH were calculated at the TD-CAM-B3LYP level. Results indicate that H（C4 H2 S）n H have three kinds of ground state geometries： spiral-rising structure, circular structure and slightly curvulate banded structure. The first two structures are cis and the last one is trans; the circular structure has C2 symme try, while the other two structures have C1 symmetries. Besides, the calculated absorption spectra and emission spectra of H（C4 H2S）,, H agree very well with relevant experimental val- ues.