外电场作用下的五氯酚分子结构和电子光谱的研究

为研究外电场对环境毒物氯酚类化合物的分子结构、化学键和电子光谱产生的影响, 本文采用密度泛函(DFT)B3LYP方法在6-311++G(d,p)基组水平上优化并计算了不同外电场(0—0.025 a.u.) 作用下五氯酚分子的基态几何结构、电偶极矩和分子总能量, 在此基础上利用含时密度泛函(TDDFT)在同一基组下研究了五氯酚(pentachlorophenol, PCP)的紫外吸收光谱, 并与文献中给出的苯酚的紫外吸收峰的波长进行了比较, 最后对PCP分子的前10个激发态的波长和振子强度受外电场作用的的影响规律进行了研究. 结果表明, 分子几何构型与电场大小呈现强烈的依赖关系, 分子偶极矩随着外电场的增强先减小后增加, 而分子总能量随着外电场的增强先增加后减小; PCP的紫外吸收峰相对苯酚出现了红移, 其激发态的振子强度随着电场的增强而减小、紫外吸收峰也出现红移.

Molecular structure and electronic spectrum of pentachlorophenol in the external electric field

In order to study the influence of external electrical field on molecular structure, chemical bond and electronic spectrum of environmental poison chlorophenol, the method B3LYP of the density functional theory (DFT) at 6-311++G(d, p) level is used to calculate geometrical parameters, dipole moments and total energies of the ground state of pentachlorophenol molecule under different external electric fields (from 0 to 0.025 a.u.) in this article. On this basis, the UV absorption spectra of pentachlorophenol (PCP) are studied using the time-dependent density functional theory (TDDFT) in the same fundamental group and compared with the ultraviolet absorption peak of phenol given in the literature. Finally, the rules of external electric field influencing wavelengths and oscillator strengths of the first ten excited states of a PCP molecule are studied. The results show that molecular geometry is strongly dependent on the field intensity, the molecular dipole moment is proved to be first decreasing, then increasing and the total energy first increasing then decreasing with the increase of the field intensity. Compared with the ultraviolet absorption peak of phenol, that of PCP is red-shifted. The oscillator strength of excited state of PCP is proved to be decreasing, and the ultraviolet absorption peak is also red-shifted with the increase of the field intensity.