在同态联共晶体中Diazabicyclo[2.2.2]octane的旋转动力学:输入式和输入式效应
Luca Catalano1,2, Salvador Perez-Estrada1, Hsin-Hua Wang3
1Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095, United States.
Journal of the American Chemical Society
|December 20, 2016
概括
这项研究揭示了体结合的共晶体中旋转能量障碍的独特体和体贡献. 研究人员确定了两动态晶体中报告的最低激活能量,从而提供了对分子动态的洞察力.
科学领域:
- 水晶工程
- 超分子化学
- 固态化学
背景情况:
- 素结合 (XB) 是晶体工程中的一个关键的非共价相互作用.
- 了解共晶体的旋转动力学对于设计分子机器和材料至关重要.
- 三乙烯化物 (TrX) 和二氧化 (dabco) 形成具有受控分子运动潜力的共晶体.
研究的目的:
- 阐明XB共晶体中旋转自由能量障碍的和组成部分.
- 研究TrX (X=I, Br, Cl) 和dabco之间的1:1共晶体的形成和结构特征.
- 确定这些同晶体结构中的dabco的旋转动力学和激活参数.
主要方法:
- 通过溶剂蒸发和机械化学方法合成共晶体.
- 单晶X射线衍射用于结构分析.
- 四极回声2H NMR和可变温度1H NMR旋转放松 (VT 1H T1) 用于旋转动力学研究.
主要成果:
- 成功地形成了Tri-dabco和TrBr-dabco的同态1:1共晶 (4a和4b);没有获得与TrCl的共晶.
- 结构分析显示"旋转的顶部在三脚架上"的图案和包装相互作用的微妙差异.
- 核磁共振研究显示,在六倍的潜在能量表面上,Dabco旋转速度很快,激活能量低 (Ea为4b=0.71 kcal mol-1),为两极力晶体报告的最低值.
- 耳环方程分析产生了小的负激活 (ΔS‡ = -3.0 cal mol-1 K-1) 和明显的激活 (ΔH‡为4a = 0.95 kcal mol-1,4b = 0.54 kcal mol-1).
结论:
- 同形共晶体的旋转腔内的微妙的硬体差异决定了不同的旋转激活能量.
- 该研究成功地解开了XB共晶体中旋转障碍的和贡献.
- 这些发现提供了对固体分子运动的基本理解,
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