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采用密度泛函理论(DFT)-B3LYP/6-31G(d)方法研究了给、吸电子基团对称和不对称封端对9,9’-螺双芴光电性质的影响.全优化得到了9,9’-螺双芴封端前后各分子的稳定构型,分析了各种封端系列的HOMO-LUMO能隙.结果表明,以给电子基团噻吩和吸电子基团噁二唑不对称封端作用于9,9’-螺双芴,能使LUMO能量大幅降低,HOMO能量略有升高,能隙明显变窄.不对称封端低聚9,9’-螺双芴分子[T(SBF)nO,n=1～4]在相同计算水平下的全优化结果表明吸、给电子基团的电荷比随n的增大而递增,揭示了给、吸电子基团间存在分子内电荷转移(ICT),且这种电荷转移在低聚物中得到加强.计算得到的电离势、电子亲和势、空穴抽取能、电子抽取能和重组能等相关能量,证明了在主链上形成的载流子传输通道提高了空穴和电子传输的能力.用TD-DFT和ZINDO方法计算了T(SBF)nO(n=1～4)的吸收光谱,随着n的增大而激发光所需的能量减小,光谱红移,吸收强度增大;用CIS/6-31G(d)方法优化得到了不对称封端9,9’-螺双芴S1激发态构型,结果表明,激发态的平面化程度比基态高.
The effects of the symmetry and asymmetric end-capping of electron-withdrawing electron groups on the photoelectric properties of 9,9’-spirobifluorene were investigated by using density functional theory (DFT) -B3LYP / 6-31G (d) The stability of each molecule before and after 9,9’-spirobifluorene end-capping was analyzed, and the HOMO-LUMO energy gaps of various end-capped series were analyzed. The results showed that with the electron donating group thiophene and the electron-withdrawing group oxadiazole not Symmetric endcapping effect on 9,9’-spirobifluorene, LUMO energy can be significantly reduced, HOMO energy slightly increased, the band gap was significantly narrower.Asymmetric-terminated oligomeric 9,9’-spirobifluorene molecule [ T (SBF) nO, n = 1 ~ 4] The results of the whole optimization at the same computational level show that the charge-to-electron group charge-to-charge ratio increases with increasing n, revealing the presence of molecules Internal charge transfer (ICT), and this charge transfer is enhanced in the oligomer.Calculated ionization potential, electron affinity, hole extraction energy, electron extraction energy and recombination energy and other related energy, proved that the main The carrier transport channel formed on the chain enhances the hole and electron transport ability.The absorption spectra of T (SBF) nO (n = 1 ~ 4) are calculated by TD-DFT and ZINDO methods. With the increase of n While exciting light The required energy is reduced, the red shift of the spectrum and the absorption intensity are increased, and the excited state of 9,9’-spirobifluorene S1 is optimized by the method of CIS / 6-31G (d). The results show that, The excited state is more planar than the ground state.