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采用密度泛函理论B3LYP/6-31+g(d)方法对二聚α、β-并三噻吩衍生物的18个分子(a~j2)进行几何构型优化,对其最优构型采用TD-DFT(TDB3LYP/6-31+g(d))计算电子吸收光谱,用有限场FF方法及自编程序计算二阶非线性光学(NLO)性质。计算结果表明,增加共轭链的含乙烯桥的二聚并三噻吩比不含乙烯桥者,βμ(或β0)大1.6—5.3倍;在含乙烯桥二聚α、β-并三噻吩分子(母体分子)末端引入含C=C或C≡C的基团(如-C≡CH与-C=C(CN)_2),比引入强供电子基团(如-N(CH_2CH_3)_2)、单纯吸电子基(如F原子)βμ(或β0)更大;尤其是端接-C=C(CN)2基团的二聚α、β-并三噻吩衍生物,其βμ(或β0)值为104数量级个原子单位(10-29esu),与母体分子相比βμ增大4.8~19.6倍,更有利于改善体系的二阶非线性光学性质,从而可获得良好的非线性光学材料.
The optimized structures of 18 molecules (a ~ j2) of dimeric α, β-and tris-thiophene derivatives were optimized by density functional theory B3LYP / 6-31 + g The electron absorption spectrum was calculated by TD-DFT (TDB3LYP / 6-31 + g (d)), and the second-order nonlinear optical (NLO) properties were calculated by finite field FF method and self-programming. The calculated results show that the dimeric dithiotrityl containing ethylene bridges with conjugated chains is 1.6-5.3 times larger than βμ (or β0) than those without ethylene bridges. In the copolymer containing ethylene bridge dimerized α, β- (Such as -C≡C and -C≡C) groups (such as -C≡CH and -C═C (CN) _2) are introduced at the end of the (parent molecule) to introduce a strong electron donating group (such as -N (CH_2CH_3) _2) (Such as F atom) βμ (or β0); especially dimeric α, β-and tris-thiophene derivatives terminated with -C = C (CN) 2 groups, the βμ ) Value of 104 orders of magnitude units of atomic units (10-29esu), compared with the parent molecular βμ increased 4.8 ~ 19.6 times, more conducive to improve the system of second-order nonlinear optical properties, resulting in a good nonlinear optical material.