外场作用下邻苯二甲酸二丁酯的分子结构和光谱研究

Molecular structure and spectrum of dibutyl phthalate in an external electric field

邻苯二甲酸二丁酯(dibutyl phthalate,DBP)是增塑剂的主要成分之一.为研究外电场对环境毒物增塑剂类化合物的分子结构和光谱产生的影响,本文采用密度泛函(density functional theory,DFT)B3LYP方法在6-311++G(d,p)基组水平上优化了不同静电场(0—0.020 a.u.)作用下DBP分子的基态几何结构,在此基础上利用同样的方法计算了DBP分子的电偶极矩、分子总能量和红外(infrared,IR)光谱,最后利用含时密度泛函(time-dependent density functional theory,TDDFT)在同一基组下研究了不同外电场对DBP分子紫外-可见(UV-Vis)吸收光谱产生的影响,并与实验测得的光谱图进行了比较.结果表明,在外电场的作用下,分子结构变化剧烈,电偶极矩增大,分子总能量减小,红外光谱吸收峰出现红移或蓝移,分子的摩尔吸收系数重新分配,振动斯塔克效应(vibrational stark effect,VSE)明显;随着外电场的增强,分子UV-Vis光谱的吸收峰红移显著,振子强度剧烈下降.

Dibutyl phthalate（DBP） is the main component of the plasticizers. In order to study the influence of an external electrical field on the molecular structure and spectra of DBP, the method B3 LYP of the density functional theory（DFT） at 6-311＋＋G（d, p） level has been used in this paper to calculate its geometrical parameters and infrared（IR）spectra, in the ground state of DBP molecule under different external electric fields（from 0 to 0.020 a.u.）. On this basis, the UV-Vis absorption spectra of DBP are studied using the time-dependent density functional theory（TDDFT）in the same fundamental groups and compared with the ultraviolet（UV） absorption peak of the molecules measured by UNICO ultraviolet and visible spectrophotometer. The rule of variation of wavelength and oscillator strength of the first twenty-six excited states of a DBP molecule under the influence of the external electric fields are studied. Results show that the molecular geometric parameter is strongly dependent on the external field intensity, and the dipole moment of DBP is proved to be sharply increased, and the total energy first decreases with the increases of the external field intensity; the significant negative（＂red＂） and positive（＂blue＂） frequency shifts are observed, i.e., vibrational Stark effect（VSE） is shown obviously; the ultraviolet absorption peaks of the excited states of DBP show an observable red shift,and the oscillator strength decreases sharply with increasing field intensity.