摘要
运用密度泛函(DFT/B3LYP)方法对三种吸电子基(—C6H5、—CN、—Cl)取代的8-羟基喹啉锂(Liq)所形成的18种衍生物进行对比,从中找出最稳定的三种衍生物,并在此基础上应用含时密度泛函(TD-DFT)方法和单激发组态相互作用(CIS)分析了取代基对Liq前线分子轨道和电子光谱的影响。结果表明:吸电子取代基主要影响所在环的前线分子轨道,其影响程度和取代基的吸电子能力有关;同时取代位置的不同和取代基的共轭效应会导致电子光谱的移动方向不同,取代基在苯酚环上时使Liq电子光谱蓝移,而在吡啶环上时使Liq电子光谱红移,取代基共轭效应大电子光谱红移。该计算结果与实验结果吻合。
Studies and applications of organic light emitting display （OLED） have indicated that it is one of the promising technologies of planar display. Metaloquinolates with high stability and high fluorescence quantum efficiency are widely applied in organic EL devices. The experimental and theoretical investigations of these complexes have been widely implemented, while the theoretical study of Liq attracted little attention. The singles configuration interaction （CIS）and the time-dependent density functional theory （TD-DFT） are main methods for theoretical study on molecular excited state and electronic spectrum. In this paper, the frontier molecular orbit and electronic spectrum of Liq and its derivates are calculated by CIS and TD-DFT method. The effect of substituting group on the frontier molecular orbit and the electronic spectrum were analyzed. All this will provide a theoretical basis for the molecular structure design of organic electroluminescent materials. We designed 18 kinds of derivates which were obtained by substitution of three kinds electron-withdrawing group （-C6H5,-CN or-Cl ） at different position, respectively. The derivates of 8-hydroxyquioline lithium （Liq） were investigated quantitatively by means of DFT/B3LYP. The most stable substituted derivates （2-C6H5-Liq, 5-CN-Liq and 6-Cl-Liq） were selected according to the lowest energy rule. Basing on that, the absorption spectrum is calculated by TD-DFT, and the structures of excited states were optimized by CIS method. On the optimized-structures of excited states, the emission wavelength was predicted by TD method. And then the effect of substituting group on the frontier molecular orbit and electronic spectrum were discussed. The results indicated that the electronic withdrawing group affected mainly the electron cloud distribution of the frontier molecular orbit, which was correlated to the electronic withdrawing ability of ligand. The electron-withdrawing group on phenoy ring makes the HOMO-LUMO band gap increased. The increase of band gap then leads to a blue shift of electronic spectrum. Substitute position was related to electronic spectrum shift. The electron-withdrawing group on pyriding ring makes the HOMO-LUMO band gap decreased. The decrease of band gap then leads to a red shift of electronic spectrum. The simulative peaks at 269.94, 373.26 nm of the UV absorption spectra and the peak at 461.7 nm of emission spectra of Liq are closed to the peaks at 259.8, 363.8 nm of the experimental UV absorption spectra and the peak at 452 nm of emission spectra of Liq. It indicates that the TD-DFT method do well in predicting the electronic spectrum of metaloquinolates.
出处
《发光学报》
EI
CAS
CSCD
北大核心
2007年第2期193-197,共5页
Chinese Journal of Luminescence
基金
国家自然科学基金(20671068)
山西省自然科学基金(20041066)
山西省回国人员基金(200523)
山西省科技攻关项目(2006031121)资助项目
