Dipartimento di Chimica, Università di Roma La Sapienza, P. le A. Moro 5, 00185 Roma, Italy.
J Chem Phys. 2011 Aug 21;135(7):074505. doi: 10.1063/1.3625920.
X-ray absorption spectroscopy (XAS) has been used to unveil the bromide ion local coordination structure in 1-alkyl-3-methylimidazolium bromide [C(n)mim]Br ionic liquids (ILs) with different alkyl chains. The XAS spectrum of 1-ethyl-3-methylimidazolium bromide has been found to be different from those of the other members of the series, from the butyl to the decyl derivatives, that have all identical XAS spectra. This result indicates that starting from 1-buthyl-3-methylimidazolium bromide the local molecular arrangement around the bromide anion is the same independently from the length of the alkyl chain, and that the imidazolium head groups in the liquid ILs with long alkyl chains assume locally the same orientation as in the [C(4)mim]Br crystal. With this study we show that the XAS technique is an effective direct tool for unveiling the local structural arrangements around selected atoms in ILs.
X 射线吸收光谱（XAS）已被用于揭示不同烷基链的 1-烷基-3-甲基咪唑溴盐 [C(n)mim]Br 离子液体（ILs）中溴离子的局部配位结构。结果表明，1-乙基-3-甲基咪唑溴盐的 XAS 谱与该系列的其他成员不同，从丁基到癸基衍生物的 XAS 谱均相同。这表明，从 1-丁基-3-甲基咪唑溴盐开始，溴阴离子周围的局部分子排列与烷基链的长度无关，并且长烷基链的液体 ILs 中的咪唑鎓头基在局部上与 [C(4)mim]Br 晶体中的相同。通过这项研究，我们证明了 XAS 技术是一种有效的直接工具，可以揭示 ILs 中选定原子周围的局部结构排列。
