离子液体[BMIM]Br与[BMIM][BF_4]配比浓度对Br^-离子电荷转移的调节  

Effect of the Ratio between Ionic Liquids [BMIM]Br and [BMIM][BF_4 ] on the Charge Transfer of Br^-

作　　者：马静远[1] 邹杨[1] 姜政[1] 黄宇营[1] 

机构地区：[1]中国科学院上海应用物理研究所,上海201204

出　　处：《物理化学学报》2013年第8期1618-1622,共5页Acta Physico-Chimica Sinica

基　　金：国家自然科学基金(11079007;11005148;10705046);中国科学院知识创新工程重大交叉项目(KJCX2-YW-N43)资助~~

摘　　要：利用X射线吸收精细结构光谱(XAFS)及紫外吸收光谱两种方法,分析了离子液体1-丁基-3-甲基咪唑溴盐([BMIM]Br)中逐渐掺入1-丁基-3-甲基咪唑四氟硼酸盐([BMIM][BF4])时,Br-阴离子与咪唑阳离子之间氢键作用及电荷偏移量的改变.随着[BMIM][BF4]加入量增多,Br元素XAFS近边(XANES)显示吸收峰降低,吸收边位置向低能端位移0.9eV;扩展边(EXAFS)算出径向结构显示Br与近邻原子间平均配位数降低、平均键长增长;紫外光谱也有明显蓝移减色效应.这些结果都表明BF-4的掺入改变了Br-与阳离子间的电荷偏移量,负电荷更多地转移到Br-上,量化计算的数据同样支持该结论.We analyzed the change of hydrogen bonding between Br- and imidazolium cations when the ionic liquid 1-butyl-3-methylimidazolium bromide （[BMIM]Br） was gradually mixed with 1-butyl-3- methylimidazolium tetrafluoroborate （[BMIM] [BF,]） using X-ray absorption fine structure （XAFS） and ultraviolet absorption spectroscopies. As the content of [BMIM][BF,] increased, the intensity of the K-edge main peak of Br reduced in X-ray absorption near edge structure （XANES） spectra, and the absorption edge moved 0.9 eV to lower energy. Meanwhile, the radial structure given by extended X-ray absorption fine structure （EXAFS） indicated that the distribution number reduced and average hydrogen bond length increased. UV spectra showed a clear blue shift and peaks decreased in intensity as the content of [BMIM][BF,] increased. All of these results indicate that more negative charge was transferred to Br- as the content of [BMIM][BF,] increased. The data obtained from quantum chemical calculations also support this conclusion.

关 键 词：离子液体 电荷转移 X射线吸收精细结构光谱 吸收边 紫外光谱 

分 类 号：O645[理学—物理化学]