Lesot P, Emsley JW, Ouvrard JM, Curzon E
Department of Chemistry, University of Southampton, Southampton, SO17 1BJ, United Kingdom.
J Magn Reson. 1998 Jul;133(1):166-72. doi: 10.1006/jmre.1998.1452.
A general method is presented of converting second-order fluorine-19 spectra of liquid crystalline samples into first-order spectra. This is achieved by recording a 19F COSY spectrum with a multiple pulse dipolar reducing sequence (MPS) operating in the t1 period, leading to a F1 projection which is first order. The method is illustrated by recording spectra on a sample of 1,3-dichloro-4-fluorobenzene dissolved in the nematic solvent ZLI 1167. Experiments have been done in which the MPS is either the MREV-8 or Flip-Flop-16 sequence. The first-order F1 projections are analyzed to give reduced total 1H-19F couplings, KCSTHFij and the reduction factors, KCS, are obtained by comparison with the THFij available from an analysis of the ordinary 1D spectrum. The reduction factors are compared with values predicted by average Hamiltonian theory (AHT). The reasons for the differences found between observed and predicted values of KCS have been investigated by performing numerical simulations of the 2D MPS COSY experiments. Copyright 1998 Academic Press.
本文提出了一种将液晶样品的二阶氟-19光谱转换为一阶光谱的通用方法。这是通过在t1周期使用多脉冲偶极矩降低序列（MPS）记录19F COSY光谱来实现的，从而得到一阶的F1投影。通过记录溶解在向列型溶剂ZLI 1167中的1,3-二氯-4-氟苯样品的光谱来说明该方法。实验中使用的MPS序列为MREV-8或翻转-16序列。对一阶F1投影进行分析，得到简化的总1H-19F耦合常数KCSTHFij，并通过与从普通一维光谱分析中获得的THFij进行比较，得到降低因子KCS。将降低因子与平均哈密顿理论（AHT）预测的值进行比较。通过对二维MPS COSY实验进行数值模拟，研究了KCS观测值与预测值之间差异的原因。版权所有1998年学术出版社。
