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采用密度泛函理论B3LYP/6-31+G(d,p)方法对二聚α、β-并三噻吩衍生物的15个分子(a~g2)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三阶非线性光学(NLO)性质.计算结果表明,在乙烯分子(反式)两侧分别引入α-并三噻吩、β-并三噻吩基团(c分子)比单纯引入相同的α-并三噻吩(a分子)或β-并三噻吩(b分子)基团,更有利于增大其三阶非线性光学(NLO)性能.在含乙烯桥二聚α、β-并三噻吩(母体分子)结构的末端,端接含C=C或C≡C的基团(如-C≡CH与-C=C(CN)_2),与端接吸电子基F原子或给电子基-N(CH_2CH_3)_2相比,能隙降值减小,最低能量吸收波长明显红移,其三阶NLO系数γ值达10~6数量级个原子单位(10~(-33)esu),显示出良好的三阶非线性光学性能,可设计成为性能良好的三阶非线性光学材料.
The geometries of 15 molecules (a ~ g2) of dimeric α, β-and tris-thiophene derivatives were optimized by density functional theory B3LYP / 6-31 + G (d, p) The electron absorption spectra were calculated by TD-DFT (TDB3LYP / 6-31 + G (d)), and the third order nonlinear optical (NLO) properties were calculated by the finite field FF method and self-programming program. (T molecule) or β-tris-thiophene (b molecule) groups were introduced into both sides of the trans-a-t- , More conducive to increasing its third-order nonlinear optical (NLO) performance at the end containing ethylene bridge dimeric α, β-and trithiophene (parent molecular) structure, terminated with C = C or C ≡ C-based (Such as -C≡CH and -C = C (CN) _2), compared with the terminal electron-withdrawing F atom or the electron-donating group -N (CH_2CH_3) _2, the energy gap decreases and the minimum energy absorption wavelength The third-order NLO coefficient γ values are in the order of 10 to 6 atomic units (10 ~ -33) esu, which shows good third-order nonlinear optical properties and can be designed into third-order nonlinear Optical materials.