基于苯溶剂化效应的多种邻苯二甲酸酯(PAEs)拉曼特征振动光谱辨识

利用密度泛函与自洽反应场理论在B3LYP/6-311G(d)水平下对16种邻苯二甲酸酯(PAEs)进行结构优化,并计算气态环境及溶剂中PAEs的拉曼光谱振动频率和去偏振度。研究显示,16种PAEs拉曼振动归属为苯环变形、酯基振动、C—C伸缩、C—H摇摆、C—H伸缩与耦合振动。其中酯基官能团出峰位置在1 700~1 780cm-1之间,拉曼峰较强,去偏振度较低(振动的对称性较强),可将酯基振动作为特征振动;但气态环境下仅12种PAEs拉曼峰之间的最小波数差大于显微拉曼光谱仪的检出限(0.2 cm-1),即利用酯基频区的去偏振度和拉曼峰不能完全辨识16种PAEs。溶剂化效应分析显示,溶剂苯对16种PAEs具有明显的溶剂化增强效应,16种PAEs拉曼峰之间最小波数差均增大到0.2 cm-1以上,且峰强增加了23%~183%,说明溶剂化效应下可利用酯基频区的去偏振度和拉曼峰辨识16种PAEs。本文的研究结果为PAEs拉曼光谱检测提供了理论依据。

Identification of the Raman Characteristic Spectrum Vibrations for Various PAEs Based on Benzene Solvent Effect

By means of density functional theory and self-consistent reaction field in B3LYP/6-311G(d) method, the 16 kinds of phthalate esters (PAEs): BBP,DBP,DCHP,DEHP,DEP,DIDP,DINP, DMP, DNOP, BMPP, DAP, DHP, DIPrP, DMEP, DPhP and DPP were selected and their structures were optimized. Their Raman vibrational frequencies and depolarization in atmosphere and 6 kinds of solvents were calculated. The results show that Raman vibrations of 16 PAEs are assigned to ring deformation,ester base deformation,C-C stretching,C-H wiggle,C-H stretching and of these several patterns. The peak position of the ester base functional group is relatively fixed in 1 700－1 780 cm^-1. Raman peak of ester base vibration is stronger,and the polarization degree is lower (the symmetry of vibration was stronger). Therefore, the ester base vibration can be regarded as the characteristic vibration. But the minimum differential wave numbers of only 12 kinds of PAEs are larger than micro Raman spectrometer detection limit (0.2 cm^-1), so the 16 kinds of PAEs can not be fully identified by depolarization and the Raman peak of ester base vibration frequency area. Solvent effect analysis shows that benzene solvent has obvious enhanced solvent effects on 16 kinds of PAEs. The minimum differential wave numbers of 16 kinds of PAEs increase to 0.2 cm^-1 above and the Raman intensity increases to 23%－183%,which illustrate that the 16 kinds of PAEs can be fully identified by depolarization and the Raman peak of ester base vibration frequency area. It provides theoretical basis for the detection of PAEs Raman spectroscopy.