Humphreys Elizabeth K, Allan Phoebe K, Welbourn Rebecca J L, Youngs Tristan G A, Soper Alan K, Grey Clare P, Clarke Stuart M
Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, United Kingdom.
Gonville and Caius College , Trinity Street, Cambridge CB2 1TA, United Kingdom.
J Phys Chem B. 2015 Dec 10;119(49):15320-33. doi: 10.1021/acs.jpcb.5b08248. Epub 2015 Dec 2.
Neutron diffraction with isotopic substitution has been used to characterize the bulk liquid structure of the technologically relevant electrolyte solution, 1 M tetrapropylammonium bromide (TPA Br) in acetonitrile (acn), and of pure deuterated acetonitrile. Empirical potential structure refinement modeling procedures have been used to extract detailed structural information about solvent-solvent, solvent-ion, and ion-ion correlations. Analysis of the refined data shows the expected local dipolar conformation of acn in the pure solvent. This short-range dipolar ordering is also present within the solutions of TPA Br in acn, and it affects how the solvent orders itself around the ions. The solvation numbers of the TPA cations and the bromide anions are deduced, 8 and 5, respectively, as are the orientations of the solvent molecules that surround the ions. Evidence for ion association is also presented, with nearly two-thirds of the ions in the system being in associated pairs or clusters.
利用同位素取代的中子衍射来表征具有技术相关性的电解质溶液（1M四丙基溴化铵（TPA Br）在乙腈（acn）中）以及纯氘代乙腈的本体液体结构。采用经验势结构精修建模程序来提取有关溶剂-溶剂、溶剂-离子和离子-离子相关性的详细结构信息。对精修数据的分析显示了纯溶剂中乙腈预期的局部偶极构象。这种短程偶极有序也存在于TPA Br在乙腈中的溶液中，并且它影响溶剂在离子周围的排列方式。推导出TPA阳离子和溴离子的溶剂化数分别为8和5，以及围绕离子的溶剂分子的取向。还给出了离子缔合的证据，系统中近三分之二的离子处于缔合对或簇中。
