Shahkhatuni Astghik A, Ma Kefeng, Weiss Richard G
Department of Chemistry, Georgetown University, Washington, D.C. 20057-1227, USA.
J Phys Chem B. 2009 Apr 2;113(13):4209-17. doi: 10.1021/jp810793n.
The ordering parameters of selected solutes from NMR spectroscopic measurements have been assessed in the thermotropic and amphotropic smectic liquid-crystalline phases of a wide structural range of phosphonium salts with three equivalent long n-alkyl chains, one shorter chain, and various anions. The nature of the added liquids that convert the salts to amphotropic phasesalcohols and other small organic moleculesand their concentrations have been determined. These factors are correlated with the NMR-derived parameters in order to understand how the phases can be optimized to maximize information about the solutes. The various salts cover a range of liquid crystallinity from -40 to 100 degrees C. The phosphonium salts are easily aligned in the strong magnetic fields of the spectrometers. In several of the systems, a coexistence of isotropic and anisotropic phases is observed over a wide range of temperatures. The order parameters of the amphotropic liquid-crystalline phases vary from high to very low values, and some of the systems provide good spectral resolution for the solute molecules. Also, structural and orientational parameters of a model molecule, (13)C-enriched acetonitrile, have been calculated in various systems in order to evaluate more precisely the applicability of the host systems for determining solute structures by NMR. The results, in toto, indicate that several of the phosphonium salts are very promising as hosts to determine solute structures.
通过核磁共振光谱测量得到的选定溶质的有序参数，已在具有三条等效长正烷基链、一条较短链和各种阴离子的多种结构的鏻盐的热致和兼性近晶型液晶相中进行了评估。已确定了将盐转化为兼性相的添加液体（醇类和其他小有机分子）的性质及其浓度。这些因素与核磁共振衍生参数相关联，以便了解如何优化这些相，以最大限度地获取有关溶质的信息。各种盐的液晶范围为-40至100摄氏度。鏻盐在光谱仪的强磁场中很容易排列。在几个体系中，在很宽的温度范围内观察到各向同性相和各向异性相共存。兼性液晶相的有序参数从高值到非常低值不等，并且一些体系为溶质分子提供了良好的光谱分辨率。此外，为了更精确地评估主体体系通过核磁共振确定溶质结构的适用性，已在各种体系中计算了模型分子（富含(13)C的乙腈）的结构和取向参数。总体结果表明，几种鏻盐作为确定溶质结构的主体非常有前景。
