中心核对四硫富瓦烯端基星型分子结构和性质的影响

采用密度泛函理论方法对以四硫富瓦烯(TTF)为端基、苯乙烯为桥的5种不同中心核(富电子核:氮、三聚咔唑及三聚吲哚;缺电子核:三嗪及三聚喹喔啉)构成的星型三支D-π-A型化合物的几何结构、电子吸收光谱及电荷转移性质进行了研究.结果表明,通过改变中心核的类型,可有效调节LUMO能级,改变能隙的大小.电荷差分密度及跃迁密度矩阵分析结果表明,两支内的TTF端基与核到共轭桥链的电荷转移跃迁及少量的π→π*跃迁对高能吸收带有贡献;缺电子核化合物的低能吸收峰主要是TTF端基到桥链和中心核的电荷转移跃迁贡献,不同于富电子核化合物明显的TTF贡献的支内定域电荷转移跃迁.重组能计算表明,除化合物NST(中心核为氮)外,其余4个化合物的空穴重组能(λh)与电子重组能(λe)相当,中心核为三聚咔唑的化合物CST重组能相对较小.

Impact of Core on Structures and Properties of Tetrathiafulvalene Terminated Star-shaped Molecules

The geometries, electronic absorption spectra and charge transfer properties of five novel star-shaped compounds with different core(electron-rich core: nitrogen, triazatruxene and triindole; electron-deficient core: 1,3,5-triazine and triquinoxaline), styrene as bridge and tetrathiafulvalene(TTF) as a terminal group, were studied with density functional theory(DFT) method. The results show that LUMO levels and energy gaps can be adjusted effectively via altering the cores. The time-dependent DFT calculation indicates that there are two absorption bands in 300-450 nm. The results of the transition density matrix and charge difference density reveal that high energy excitation mainly arises from charge transfer from TTF donor moiety to core and bridge moiety. The low-lying excitations in electron-deficient core compounds are predominantly TTF donor-bridge and core charge transfer transition from two intra-branch. This differs from electron-rich compounds, whose low-energy transitions are assigned to prominently intra-branch localized excitation from TTF moiety. The reorganization calculations show that the hole and electronic reorganization energy are nearly equal except NST, and CST shows the lowest reorganization energy.