Castiglione Franca, Simonutti Roberto, Mauri Michele, Mele Andrea
†Department of Chemistry, Materials and Chemical Engineering "G. Natta", Politecnico di Milano, Piazza L. Da Vinci 32, 20133 Milano, Italy.
‡Dipartimento di Scienza dei Materiali, Università degli Studi di Milano Bicocca, Via Roberto Cozzi 53, 20125 Milano, Italy.
J Phys Chem Lett. 2013 May 16;4(10):1608-12. doi: 10.1021/jz400617v. Epub 2013 Apr 26.
The chemical shift of xenon (at natural abundance) dissolved in a variety of 1-butyl-3-methylimidazolium-based ionic liquids (ILs) has been measured with (129)Xe NMR spectroscopy. The large chemical shift differences observed are mainly related to the type of anion; the strongest deshielding effect is observed ILs with I(-), Br(-), and Cl(-) anions, and the strongest shielding is found for the bis(trifluoromethanesulfonyl)imide (Tf2N)-based IL. The measured (129)Xe chemical shift variations correlate well with the IL structure organization imposed by the anions and with the size of the empty voids due to charge alternation patterns. Descriptors taken from literature data on X-ray and neutron scattering, as well as single-crystal structures where available, support this interpretation. The proposed methodology adds a new investigating tool to the elucidation of the short-range order in ILs. The observed chemical shift trend provides information about how these solvents are organized.
利用¹²⁹Xe核磁共振光谱法测量了溶解在多种基于1-丁基-3-甲基咪唑鎓的离子液体（ILs）中的氙（天然丰度）的化学位移。观察到的大化学位移差异主要与阴离子类型有关；在含有I⁻、Br⁻和Cl⁻阴离子的离子液体中观察到最强的去屏蔽效应，而对于基于双（三氟甲磺酰）亚胺（[Tf₂N]⁻）的离子液体则发现最强的屏蔽效应。测量的¹²⁹Xe化学位移变化与阴离子所施加的离子液体结构组织以及由于电荷交替模式导致的空穴大小密切相关。从X射线和中子散射的文献数据以及单晶结构（如有）中获取的描述符支持了这一解释。所提出的方法为阐明离子液体中的短程有序性增添了一种新的研究工具。观察到的化学位移趋势提供了有关这些溶剂如何组织的信息。
