高场动态核极化与高旋转过渡金属离子
Björn Corzilius1, Albert A Smith, Alexander B Barnes
1Department of Chemistry and Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States.
Journal of the American Chemical Society
|March 31, 2011
概括
我们使用和加多复合体实现了-1旋转的动态核极化. 增强大小与电子磁共振 (EPR) 线宽相关,使得极化显著改善.
科学领域:
- 固态核磁共振 (NMR) 光谱学
- 电子偏磁共振 (EPR) 光谱学
- 动态核极化 (DNP) 是指动态核极化.
背景情况:
- 动态核极化 (DNP) 通过将极化从电子自旋转到核自旋转来增强NMR信号的灵敏度.
- 固体效应是DNP的一种常见机制,特别有效于对磁性偏振剂.
- 优化DNP需要了解影响极化增强的因素,例如电子过渡的线宽.
研究的目的:
- 为了研究动态核极化 (DNP) 的-1 (1H) 旋转使用魔法角旋转 (MAS) NMR.
- 通过固体效应探索使用 (Mn2+) 和加多 (Gd3+) 复合物作为DNP的极化剂.
- 为了确定DNP增强的大小和中央电子偏磁共振 (EPR) 过渡的有效线宽之间的关系.
主要方法:
- 在5特斯拉 (T) 和84克尔文 (K) 的磁磁共振光谱中记录魔法角旋转 (MAS) NMR光谱.
- 使用动态核极化 (DNP) 通过固体效应机制.
- 使用Mn2+) 和Gd3+) 复合物作为极化剂.
- 测量中心EPR过渡的有效线宽 (m(S) = -1/2 → +1/2).
主要成果:
- 使用Mn2+) 和Gd3+) 复合体实现了1H旋转的动态核极化.
- 在DNP增强的大小和中央EPR过渡的有效线宽之间观察到直接的相关性.
- 一个Gd(3+) 复合体具有狭窄的中央EPR线宽 (29 MHz) 产生了最大1H旋转增强约13.
- 这种增强效果与用窄线宽的三基来实现的效果相当.
结论:
- 中央EPR转换的有效线宽是通过固体效应优化DNP的一个关键参数.
- 具有狭窄EPR线宽的Gd(3+) 复合物是有效的极化剂,可以在MAS NMR中实现显著的1H旋转极化增强.
- 这些发现有助于开发更敏感的固态NMR光谱技术.
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