低聚芴及其衍生物吸收和发射光谱性质的量子化学研究

用DFT/B3LYP方法对低聚物(PF)_2n和(PFDBO)_n(n=1-4)体系进行了全优化,计算得到两个系列低聚物的电离能P_I(v,a)、电子亲和势E_A(v,a)、空穴抽取能E_{HP和电子抽取能EEP等相关能量,并用ZINDO和TD-DFT方法计算其吸收光谱,分析了两系列总能量和HOMO-LUMO能隙随n递增的变化规律及对低聚物稳定性和光谱性质的影响,推断高聚物的发光性质.用CIS方法优化低聚物的S1激发态结构并分析其与发射光谱的关系.计算结果表明,这两个系列低聚物激发态结构中都有使所有骨架原子共平面的趋势.由于插入CH2OCH2,使PFDBO的七元环部分发生较大的扭曲(两个苯环间成42.5°±0.5°的二面角),致使有效共轭链被破坏、能带带隙变宽、吸收发射光谱波长变短.}

Quantum Chemical Studies of Absorption and Emission Spectrocopic Properties for Oglimeric Fluorenes and Its Derivatives

We have fully optimized the structures of the oligomers of (PF)2n and (PFDBO)n (n=1—4) using DFT/B3LYP method and calculated their PI(v,a), EA(v,a), EHP , EEP . The absorption spectra data were calculated at ZINDO and TD-DFT levels of theory. We analyzed the rules to the variation of their HOMO-LUMO energy gap with n rising and how the energy gap reflected the spectral properties of the oligomers to deduce the spectral properties of their polymers. We optimized the S1 excited geometries and studied the emission spectra. Moreover, in the excited geometries all the framework atoms in a molecule are apt to coplanar. Above all, the dramatically twisted segment of seven-membered-ring in PFDBO(dihedral angel between it′s two phenyl ring is 42.5°±0.5°), because of CH2OCH2 caused the conjugated backbone broken. So the energy gap of it is broader, which makes in the max absorption and emission wavelengths of PFDBO shorter than PF′s.