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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.

一种新颖的二维核磁共振实验，即状态相关的二维核磁共振，应用于液晶样品，以研究液晶分子的结构和动力学。第一年，对核磁共振探头的微波部分进行了改造，以提高温度跳跃的效率。结果，我们成功获得了4'-甲氧基亚苄基-4-乙酰氧基苯胺（APAPA）和4'-乙氧基亚苄基-4-正丁基苯胺（EBBA）的向列各向同性相相关二维核磁共振谱。第二年，我们重点研究液晶分子的结构和动力学，取得了以下成果： 1．从向列相到各向同性相的相变在10毫秒内完成，从而可以单独观察APAPA中单个质子的偶极图案。 2．对于 α 甲基质子，观察到强度比为 1:2:1 的三重态图案。这一事实表明存在具有相等偶极耦合值的三个质子。 2,6 和 3,5 芳香质子的双峰模式清晰可见，分裂频率为 9.7 kHz，APAPA.3 的有序参数确定为 0.41。观察到由于自旋交换效应而导致的横截面混合。我们发现，自旋交换在芳香环（被认为是液晶分子的核心基团）内比在芳香质子和α甲基质子之间更有效地发生。4。谱分析可以针对具有少量自旋的子自旋系统而不是整个自旋系统进行。5．通过使用直径 3 mm 的样品管，EBBA 从向列相到各向同性相的相变在 5 毫秒内完成，并且单独测定丁基的各个质子的偶极分裂。