Cation and anion substitution effects on the ultrafast dynamics of interionic interaction in imidazolium based ionic liquids  

作　　者：LU Rong WANG Wei YU AnChi 

机构地区：[1]Department of Chemistry, Renmin University of China, Beijing 100872, China

出　　处：《Science China Chemistry》2011年第9期1491-1497,共7页中国科学（化学英文版）

基　　金：supported by the National Natural Science Foundation of China (20733001,20803092);the Fundamental Research Funds for the Central Universities;the Research Funds of Renmin University of China (10XNI007,10XNJ008)

摘　　要：Room-temperature Ionic Liquids(ILs) have numerous unique properties that differ from those of conventional molecular solvents.Although the unique properties of ILs have been suggested to origin from their microscopic interionic interaction,detailed dynamics of interionic interaction of ILs has not been fully understood.Here,with the Femtosecond Optical Heterodyne-Detected Raman Induced Kerr Effect Spectroscopy(fs-OHD-RIKES),we measured the ultrafast dynamics of the interionic interaction of three typical imidazolium based ILs,1-butyl-3-methylimidazolium tetrafluoroborate([bmim][BF4]),1-butyl-3-methylimidazolium hexafluorophosphate([bmim][PF6]),and 1-decyl-3-methylimidazolium tetrafluoroborate([dmim][BF4]).We observed several periods of subpicosecond oscillation in their fs-OHD-RIKES signals.Through decomposing their fs-OHD-RIKES signals into four Brownian oscillators in time domain,we explored the cation and anion substitution effects on the ultrafast dynamics of interionic interaction of ILs.We found that the cation substitution affected all the low frequency motions we observed,while the anion substitution only affected the two higher low frequency motions.Room-temperature Ionic Liquids（ILs） have numerous unique properties that differ from those of conventional molecular solvents.Although the unique properties of ILs have been suggested to origin from their microscopic interionic interaction,detailed dynamics of interionic interaction of ILs has not been fully understood.Here,with the Femtosecond Optical Heterodyne-Detected Raman Induced Kerr Effect Spectroscopy（fs-OHD-RIKES）,we measured the ultrafast dynamics of the interionic interaction of three typical imidazolium based ILs,1-butyl-3-methylimidazolium tetrafluoroborate（[bmim][BF4]）,1-butyl-3-methylimidazolium hexafluorophosphate（[bmim][PF6]）,and 1-decyl-3-methylimidazolium tetrafluoroborate（[dmim][BF4]）.We observed several periods of subpicosecond oscillation in their fs-OHD-RIKES signals.Through decomposing their fs-OHD-RIKES signals into four Brownian oscillators in time domain,we explored the cation and anion substitution effects on the ultrafast dynamics of interionic interaction of ILs.We found that the cation substitution affected all the low frequency motions we observed,while the anion substitution only affected the two higher low frequency motions.

关 键 词：Brownian oscillator ultrafast dynamics interionic interaction ionic liquid Raman induced Kerr effect spectroscopy 

分 类 号：TN911.7[电子电信—通信与信息系统] O645.4[电子电信—信息与通信工程]