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Determination of structure and dynamics of liquid crystalline molecules by state-correlated 2D NMR spectroscopy

通过状态相关 2D NMR 光谱测定液晶分子的结构和动力学

基本信息

批准号：
03640405
负责人：
NAITO Akira
金额：
$ 1.22万
依托单位：
HIMEJI INSTITUTE OF TECHNOLOGY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-03640405/
关键词：
2D NMR liquid crystal microwave temperature jump NMR phase transition dipolar pattern 双極子パタ-ン

项目摘要

A novel two dimensional NMR experiment, state-correlated 2D NMR, were applied in liquid crystalline samples to investigate the structure and the dynamics of the liquid crystalline molecules. In the first year, the microwave part of the NMR probe head was modified to improve the efficiency of temperature jump. As a results, we have succeeded to obtain nematic-isotropic phase correlated 2D NMR spectra of 4'-methoxybenzylidene-4-acetoxyaniline(APAPA) and 4'-ethoxybenzylidene-4-n-butylaniline(EBBA). In the second year, we have focused attention on investigating the structure and dynamics of liquid crystalline molecules and obtained the following results.1. Phase transition from nematic to isotropic phase was completed within 10 msec so that the dipolar patterns for individual protons in APAPA were separately observed.2. A triplet pattern with the intensity ratio of 1 : 2 : 1 was observed for the alpha methyl protons. This fact indicates the presence of three protons with equal value of dipolar couplings. A doublet pattern was clearly seen for 2,6 and 3,5 aromatic protons with a splitting frequency of 9.7 kHz and the order parameter was determined to be 0.41 for APAPA.3. A mixing of the cross sections due to the spin exchange effects was observed. We found that spin exchange occurs more efficiently within the aromatic ring, which is considered to be a core group of the liquid crystal molecule, than between the aromatic and alpha methyl protons.4. Spectral analysis could be performed for a subspin system with a small number of spins rather than the entire spin system.5. Phase transition from nematic to isotropic phase was completed within 5 msec for EBBA by using a sample tube of 3 mm diameter and the dipolar splittings for the individual protons of the butyl group were separately determined.

将一种新的二维核磁共振实验--态相关二维核磁共振实验应用于液晶样品，研究了液晶分子的结构和动力学。在第一年，核磁共振探头的微波部分进行了修改，以提高温度跳变的效率。结果，我们成功地获得了4 '-甲氧基苯亚甲基-4-乙酰氧基苯胺（APAPA）和4'-乙氧基苯亚甲基-4-正丁基苯胺（EBBA）的向列-各向同性相相关的2D NMR谱。在第二年，我们集中精力研究液晶分子的结构和动力学，并获得了以下结果.在10毫秒内完成了从双相到各向同性相的相变，从而使APAPA中单个质子的偶极模式分别被显示出来.对于α甲基质子，观察到强度比为1：2：1的三重态图案。这一事实表明存在三个具有相等偶极耦合值的质子。对于2，6和3，5芳香族质子，清楚地看到双峰图案，分裂频率为9.7 kHz，并且对于APAPA，确定顺序参数为0.41。由于自旋交换效应的横截面的混合进行了观察。我们发现，自旋交换发生更有效地在芳环，这被认为是一个核心集团的液晶分子，比之间的芳香族和α甲基质子。谱分析可以对具有少量自旋的亚自旋系统而不是整个自旋系统进行。通过使用直径为3 mm的样品管，EBBA在5 msec内完成了从正相到各向同性相的相变，并分别测定了丁基的各个质子的偶极分裂。