碱金属掺杂叔丁基杯[4]芳烃体系的结构及非线性光学性质

采用密度泛函理论B3LYP方法得到了M@t-Bu-calix4]arene和(M@t-Bu-calix4]arene)Li′(M=Li,Na,K)体系的几何结构.其中(M@t-Bu-calix4]arene)Li′(M=Li,Na,K)三个体系各有5个稳定异构体,在前三个异构体中,碱金属与t-Bu-calix4]arene分子间具有很强的相互作用能,说明了体系的稳定性.在部分(M@t-Bucalix4]arene)Li异构体中Li′原子以阴离子形式存在,整个体系表现出碱金属化物的特性.此外,使用CAMB3LYP方法计算了t-Bu-calix4]arene及碱金属掺杂后体系的非线性光学性质.结果表明,t-Bu-calix4]arene内部掺杂一个碱金属原子M后,体系的一阶超极化率(β0)有较大提高,而在配体外部又掺杂一个Li原子后,体系具有更大的β0值.其中(M@t-Bu-calix4]arene)Li′体系的MLi′-4异构体表现出最高的β0值(41827-114354 a.u.),并且随着M原子序数的增加而逐渐增大.可见,碱金属掺杂是提高t-Bu-calix4]arene非线性光学响应的一种有效策略.

Structures and Nonlinear Optical Properties of Alkali Metal-Doped t-Bu-calix[4]arene Molecules

Using density functional theory with the B3LYP functional, the optimized geometrical structures of the M@t-Bu-calix4]arene and (M@t-Bu-calix4]arene)Li' (M=Li, Na, K) compounds were obtained. Five stable isomers were identified for each bi-alkali-metal-doped (M@t-Bu-calix4]arene)Li' species. The first three lowlying isomers have considerable intramolecular interaction energies between alkali metal atoms and the t-Bucalix4]arene molecule, indicating their stabilities. According to natural bond orbital analyses, the outside Li' atom is negatively charged in some (M@t-Bu-calix4]arene)Li' structures, indicating the alkalide characteristics of these isomers. In addition, the nonlinear optical (NLO) properties of isolated and alkali-metal-doped t-Bu-calix 4]arene molecules were calculated using the CAM-B3LYP method. The results indicate that the single-doped effect of alkali metalMgreatly enhances the first hyperpolarizability (β₀) of the t-Bu-calix4]arene molecule. In particular, when another Li atomis doped outside the M@t-Bu-calix4]arene species, the resulting (M@t-Bucalix4]arene)Li' compounds exhibit larger β₀ values. Obviously, the alkali-metal-doping effect plays a crucial role. The MLi'-4 conformation has the largest β₀ value (41827-114354 a.u.) among all the (M@t-Bu-calix4]arene) Li' structural isomers, and it is found that the β₀ value of (M@t-Bu-calix4]arene)Li' gradually increases with increasing atomic number of the alkali metal M. Therefore, alkali-metal doping is an effective approach to enhance the NLOresponse of the t-Bu-calix4]arene molecule.