基于溶剂化效应的BDE-15分子振动光谱增强特征振动研究

Study on Enhancing Characteristic Vibration of the Molecular Vibration Spectrum for BDE-15 Based on Solvent Effect

利用密度泛函与自洽反应场理论在B3LYP/6-31+G(d)水平下分别计算气态及24种不同极性溶剂中4,4’-二溴二苯醚(4,4’-dibrominated diphenyl ethers,BDE-15)的分子振动光谱(红外光谱、拉曼光谱),以气态分子振动光谱为基准,筛选出对溶剂极性敏感的特征振动作为指标构建溶剂对BDE-15振动光谱溶剂化效应指标体系,探究溶剂对BDE-15分子振动频率、红外/拉曼峰强溶剂化效应及综合效应,并寻求显著增强BDE-15分子特征振动频移/强度的溶剂。研究表明:从分子振动频率角度,溶剂极性敏感的(频移>1cm-1)分子特征振动均为伸缩振和面外弯曲振,但24种溶剂对BDE-15分子振动频率溶剂化效应并不显著;从分子振动峰强角度,24种溶剂对BDE-15分子振动光谱峰强的增强效应主要发生在红外光谱的中低频区及拉曼光谱的高频区,其中起显著增强(红外/拉曼效应指标值分别大于6与5)的溶剂为醇类、乙腈、二甲亚砜、硝基苯;不同极性溶剂对BDE-15拉曼峰强溶剂化效应及综合效应指标值均表现出随溶剂介电常数增长由线性到对数的增长趋势,而红外峰强只保留低介电常数溶剂时的线性关系。利用上述BDE-15分子振动光谱峰强增强方法对BDE-153,BDE-154和BDE-209进行验证,醇类、乙腈、二甲亚砜、硝基苯对三者的振动光谱红外/拉曼峰强的效应指标值分别大于6与5,且最大峰强增倍数皆大于33,说明所建BDE-15分子振动光谱增强特征振动方法有助于进一步开展基于分子振动光谱的PBDEs同系物间辨识研究。

In this paper, the molecular vibrational spectra （IR spectra and Raman spectra） of 4, 4＇-dibrominated diphenyl ethers （BDEq5） in atmosphere and 24 kinds of solvents were calculated, at the B3LYP/6-31＋G（d） level by density functional theory and self-consistent reaction field separately. Taking the spectra in atmosphere as benchmark, the spectra information of selected characteristic vibrations which were sensitive to the polarity of solvent were used to establish the solvent effect index system for BDE-15, evaluate the specific solvent effect on vibrational frequency, IR vibrational intensity, Raman vibrational intensity and comprehensive solvent effect of each solvent and search the organic solvent which significantly affected the frequency shift/intensity. From the view of molecular vibrational frequency, the characteristic vibrations sensitive to polarity of solvent （frequency shift〉1 cm^1cm^-1 ） are all correlated with stretching and out-surface bending vibrations, the solvent effect on the vibrational frequen cy of BDE-15 of 24 kinds of solvents are all insignificant, with the index values between 1.01-1.03, compared with standard in dex value 1 of atmosphere spectra. From the view of molecular vibrational intensity, 24 kinds of solvents have all strengthen the vibrational intensities of most of vibrations, locating at the high frequency region of Raman spectra and the middle/low frequency region of IR spectra. The solvents which enhance the vibrational intensities significantly （index value greater than 6 and 5 for IR and Raman intensity separately） include alcohols, aeetonitrile, dimethyl sulfoxide, nitrobenzene, dimethyl sulfoxide. The sol vent effect index values on Raman vibrational intensity of BDE-15 increase along with the dielectric constant of solvents from linear to logarithmic growth trend, while the solvent effect index values on IR vibrational intensity only leaving the linear relationship. The comprehensive solvent effect index values have presented the similar change trend with Raman vibrational intensities. The spectra information of BDE-153, BDE-154, BDE-209 were used to authenticate the application on PBDEs of the analysis method above for BDE-15, obtaining the solvent effect index values on vibrational intensities on BDE-153, BDE-154, BDE-209 of alcohols, acetonitrile, dimethyl sulfoxide, nitrobenzene are all greater than 6 or 5, which indicate the enhancing vibrational intensities method can be used to identification research on PBDEs based on molecule vibrational spectra further.