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采用密度泛函理论(DFT)B3LYP/6-31G*方法对5,6,7顶点双取代碳硼烷桥连分子几何构型进行优化,进一步结合有限场(FF)方法,计算其二阶NLO系数.结果表明:5,6,7顶点双取代碳硼烷桥连分子受推拉电子基的影响,构型发生一定的变化,碳硼烷中两个C原子间的距离变长.碳硼烷中两个C原子取代的位置不同,影响了分子的稳定性和极化率.取代基与碳硼烷成键数较低的C原子相连的异构体,稳定性较好且具有大的极化率.5,6,7顶点双取代碳硼烷桥连分子形成一维结构,有利于分子内电荷转移,同时电荷转移过程中偶极矩变化较大,对应体系的二阶NLO系数较大.
The geometries of 5,6,7 double disubstituted carborane bridging molecules were optimized by the density functional theory (DFT) B3LYP / 6-31G * method. The second-order NLO The results show that the disubstituted carborane bridging molecules of 5,6,7 vertices are affected by the push-pull electron groups, the configuration changes a certain extent, and the distance between two C atoms in carborane becomes longer. The substitution of two C atoms in different positions affects the stability and the polarizability of the molecule.The isomers with substituents bonded to the C atoms with a lower bond number of carborane have better stability and have larger polarities The bi-substituted carborane bridging molecules at the 5,6,7 vertexes form a one-dimensional structure, which facilitates intramolecular charge transfer. At the same time, the dipole moment changes greatly during charge transfer. The second-order NLO coefficient of the corresponding system is larger .