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.

将新型的二维NMR实验（状态相关的2D NMR）应用于液晶样品中，以研究液晶分子的结构和动力学。在第一年，对NMR探针头的微波部分进行了修改，以提高温度升高的效率。结果，我们成功地获得了4'-甲氧基苯乙烯-4-乙酰氧苯胺（APAPA）和4'-乙氧基苯基苯基二苯甲酰氨基氨基（APAPA）和4'-氧基苯基二烯-4-乙酰氧苯胺的2D NMR光谱。在第二年，我们将注意力集中在研究液晶分子的结构和动力学上，并获得了以下结果。1。在10毫秒内完成了从列的相位从列到各向同性相的过渡，因此分别观察到APAPA中单个质子的偶极图。2。对于α甲基质子，观察到强度比为1：2：1的三重态图案。这一事实表明存在三个具有偶极耦合值的质子。对于2,6和3,5芳族质子，分裂频率为9.7 kHz的双重图案清楚地看到了双重图案，并且确定apapa.3的顺序参数为0.41。观察到由于自旋交换效应而引起的横截面的混合。我们发现，与芳香族和α甲基质子之间相比，自旋交换在芳族环内更有效地发生，被认为是液晶分子的核心组。4。可以为具有少量旋转而不是整个自旋系统的亚赛系统进行光谱分析5。通过使用直径为3 mm的样品管，在5毫秒内完成了从列中从列到各向同性相的相变，并且分别确定了丁基基团各个质子的偶极分割。