TORSIONAL POTENTIALS AND FULL-DIMENSIONAL SIMULATION OF ELECTRONIC ABSORPTION SPECTRA OF para-PHENYLENEVINYLENE OLIGOMERS USING SEMIEMPIRICAL HAMILTONIANS
TORSIONAL POTENTIALS AND FULL-DIMENSIONAL SIMULATION OF ELECTRONIC ABSORPTION SPECTRA OF para-PHENYLENEVINYLENE OLIGOMERS USING SEMIEMPIRICAL HAMILTONIANS
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DOI：
10.1142/s0219633610005645
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发表时间：
2010-02-01
影响因子：
2.4
通讯作者：
Kauffmann, Harald-Friedrich
中科院分区：
文献类型：
--
作者：
Lukes, Vladimir;Solc, Roland;Kauffmann, Harald-Friedrich
基于二阶Moller-Plesset能(MP2)、密度泛函理论(DFT)和奥斯汀模1(AM1)方法，系统地研究了由两个到四个芳环构成的对苯乙炔齐聚物的电子基态扭转势能曲线。与文献的MP2计算和文献数据比较，半经验AM1方法给出了势能极小值的正确位置。然而，垂直方向的半经验AM1能垒比MP2能垒小约30%。密度泛函计算表明，优化的平面结构和势垒是MP2值的三倍。在含时密度泛函理论(TD-DFT)和从头算CI水平下由垂直激发得到的激发态势能曲线在垂直取向附近的值比在半经验Zerner中间忽略微分重叠(ZINDO)和从头算RI-CC2情况下的值增加得更快。通过半经典分子动力学模拟和谐振子取样，估算了苯环振动对吸收光谱扭转展宽的影响。模拟光谱与实验吻合较好，可以估算分子的构象分布。
A systematic study of torsional potential curves in electronic ground state based on second-order Moller-Plesset energy (MP2), density functional theory (DFT), and Austin mode 1 (AM1) methods is presented for para-phenylenevinylene oligomers constructed from two to four aromatic rings. The semiempirical AM1 approach gives the correct location of potential energy minima in comparison with the reference MP2 calculations and literature data. However, the semiempirical AM1 energy barriers at perpendicular orientation are ca. 30% smaller than the MP2 ones. The DFT calculations indicate optimal planar structures and the barriers are three times higher than MP2 values. Excited-state potential energy curves evaluated from vertical excitations at the time-dependent density functional theory (TD-DFT) and ab initio CI levels exhibit much steeper increase of values in the vicinity of perpendicular orientation than in the semiempirical Zerner's intermediate neglect of differential overlap (ZINDO) and ab initio RI-CC2 cases. The effects of vibrational motion of phenylene rings on the torsional broadening of absorption spectra were estimated from semi-classical molecular dynamics simulations and harmonic oscillator sampling. The simulated spectra agree well with the experiment and allow estimating the conformer distribution of the molecules.