摘要
首次采用密度泛函理论(DFT)中的B3LYP方法,在6-31G(d)水平上对并五噻吩进行了构型优化,并作振动分析,未出现虚频。频率分析得到分子红外光谱和拉曼光谱,同时也得到分子的HOMO-LUMO能隙为3.86eV,所得计算结果与实验值基本符合。利用含时密度泛函理论(TDDFT)计算其激发态,得到振荡强度最大的五个允许跃迁的单激发态,所有激发态光谱均在紫外波段,故在可见光区域分子相对稳定,不易光致分解。对前线分子轨道HOMO和LUMO分析得到,HOMO到LUMO的跃迁是电子从C原子转移到S原子上,C—C原子之间形成离域键,这正是并五噻吩区别于一般有机材料而具有导电性的根本原因。结果表明:相对于并五苯,并五噻吩具有更高的稳定性,同时具有很好的导电性能和发光性能,是新一类有机半导体材料。
Pentacene is one of the most intensively studied systems among various organic semiconductors, for its relatively high field effect mobility and its ability to form ordered films. Nevertheless, pentacene suffers from the disadvantages of oxidative instability and, for display applications, a strong absorbance exists throughout the visible spectrum. Where photoinduced decomposition reactions could occur, this absorbance would make pentacene sensitive to most visible light. Compared to pentacene, there is an important small molecule the high polarizability of sulfur electrons in the thiophene rings. From the molecule structure, it can be analyzed that pentathienoacene （PTA） has high stability than pentacene owing to PTA＇s large band gap. These performances indicate PTA may have potential application in future organic electronics. However, the report on its application and basal physical characteristic obtained from experiment is few, and its theoretic research is much less. Quantum chemistry calculation can provide credible and valuable information for molecule study. In this paper, PTA molecule was calculated, including geometry model, infrared spectra, Raman spectra, HOMO-LUMO gap and the frontier molecular orbits by density function theory （DFT） for the first time, so the results can provide some reference informations for the future organic devices materials design theoretically. The infrared spectra and Raman spectra have been discussed and the spectra peaks of pentathienoacene were identified, the above datum on Raman spectra of PTA can provide the valuable reference for the experiment on PTA molecule identified. And at the same time, the HOMO-LUMO gap is gained：3.86 eV, which is very close to the experimental result. The five strongest allowable singlet excited states have been studied by TD- DFT. The results indicate that all the energies of excited states were located in ultraviolet region, so PTA molecule is relatively stable under the visible light illumination because photoinduced decomposition reactions can not occur. The transition electron is diverted from carbon atom to sulfur atom, which can be seen through the frontier molecular orbits of pentathienoacene. Moreover, the formation of π-delocalized band leads to increase PTA molecule conductival. The results indicate that pentathienoacene is a new kind of organic semiconductor material and has perfect luminescence and electrical properties, especially, PTA has higher stability than pentacene.
出处
《发光学报》
EI
CAS
CSCD
北大核心
2008年第5期821-826,共6页
Chinese Journal of Luminescence
基金
陕西省国际合作资助项目(2007KW-4)
