一个固态NMR,X射线衍射,和ab initio计算研究的键结构和动态的pyrazole-4-carboxylic酸链
C Foces-Foces1, A Echevarría, N Jagerovic
1Departamento de Cristalografía, Instituto de Química-Física 'Rocasolano', CSIC, Serrano, 119, E-28006 Madrid, Spain.
Journal of the American Chemical Society
|August 9, 2001
概括
固体pyrazole-4-carboxylic acid在其晶体结构中表现出动态质子秩序障碍,在低温或无形阶段过渡到质子秩序. 这种行为是由键内快速的质子转移驱动的.
科学领域:
- 固态化学 固态化学
- 分子结构和分子动力学
- 通过气结合,形成了气结合.
背景情况:
- 皮拉-4-碳素酸 (1) 是一种具有复杂结相互作用潜力的分子.
- 了解质子障碍对于预测材料特性和反应性至关重要.
研究的目的:
- 为了阐明质子在固体pyrazole-4-carboxylic acid中的结构和动态行为.
- 为了研究晶体结构,结合和质子运动之间的相互作用.
主要方法:
- 高分辨率固态-15交叉极化魔力角度旋转 (15N CMAS) 核磁共振 (NMR) 光谱.
- 在可变温度 (295 K和150 K) 的X射线晶体学.
- 关于寡合体的初始量子化学计算.
主要成果:
- 射线晶体学揭示了带有循环键和质子乱的准线性丝带,但无法区分动态和静态乱.
- 核磁共振在室温下显示出动态质子失调,其特点是键之间快速的质子转移.
- 一个低温的NMR研究表明,一个障碍-顺序的过渡,与质子定位在较低的温度,和一个无形相呈现质子顺序在快速降水.
结论:
- 该研究揭示了pyrazole-4-carboxylic acid中的动态质子障碍,由键内的快速质子转移驱动,这取决于温度.
- Ab initio计算支持与X射线数据兼容的波纹带结构,其中链运动促进质子转移.
- 无形阶段呈现出无序的结构,表明曲线和波浪纹理的组合.
相关概念视频
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