分子 tweezers:结构和机制通过中子衍射,核磁共振和标记研究在固体和溶液中的研究
Felix Schulz1, Victor Sumerin, Sami Heikkinen
1WACKER-Lehrstuhl für Makromolekulare Chemie, Technische Universität München, Lichtenbergstrasse 4, D-85747 Garching bei München, Germany.
Journal of the American Chemical Society
|November 18, 2011
概括
这项研究揭示了ansa-aminoboranes可逆的激活,证实了使用先进的光谱方法在固体和溶液状态下都存在短二键.
科学领域:
- 有机金属化学 有机金属化学
- 超分子化学 超分子化学
- 频谱学是一种光谱学.
背景情况:
- 安萨氨基是一种化合物的类,在催化中具有潜在的应用.
- 了解它们的激活机制对于开发新的化学转换至关重要.
- 研究的特定化合物,1-N-TMPH-CH(2)-2-[HB(C(6) F(5))(2)]C(6) H(4) (NHHB),具有独特的分子针结构.
研究的目的:
- 为了阐明由安萨-氨基子反向激活的机制.
- 描述NHHB在固体和溶液状态中的结构和动态特性.
- 调查二结合在激活过程中的作用.
主要方法:
- 中子衍射和热重力测量质谱仪用于固态分析.
- 核磁共振 (NMR) 光谱 (包括T(1) 放松,1D NOE,变温度和2D NOESY) 用于溶液状态的表征.
- 福利埃变换红外 (FT-IR) 光谱学用于研究动态相互作用.
- 对同位素效应研究的同位素标记同位素 (NDDB,NHDB,NDHB) 的合成.
- 理论计算以支持实验发现.
主要成果:
- 中子衍射证实了固态中短N-H···H-B二键 (1.67 Å).
- 溶液NMR研究表明,类似的H-H距离 (1.6-1.8 Å) 和固体和溶液状态之间的结构相似性.
- 同位素标记揭示了主要同位素效应,支持二结合的存在.
- FT-IR光谱学提供了在室温下动态的分子内二结合的证据.
- 没有观察到化激活的动态同位素效应,这归因于早期的过渡状态.
- 2D NOESY NMR 建议在近离子溶剂中进行快速分子间质子交换.
结论:
- 安萨-氨基NHHB通过稳定的分子内二键促进可逆激活.
- 结构和结相互作用在固体和溶液相之间保持.
- 由于没有动态同位素效应,这表明容易激活的过程具有早期的过渡状态.
- 在溶液中发生快速的分子间质子交换,表明与催化循环相关的动态行为.
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