NMR SLIC Sensing of Hydrogenation Reactions Using Parahydrogen in Low Magnetic Fields
NMR SLIC Sensing of Hydrogenation Reactions Using Parahydrogen in Low Magnetic Fields
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DOI：
10.1021/acs.jpcc.6b07555
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发表时间：
2016-12-29
影响因子：
3.7
通讯作者：
Chekmenev, Eduard Y.
中科院分区：
文献类型：
--
作者：
Barskiy, Danila A.;Salnikov, Oleg G.;Chekmenev, Eduard Y.
仲氢诱导极化（PHIP）是一种NMR超极化技术，可将核自旋极化提高几个数量级，特别适合研究氢化反应。然而，高场NMR光谱的使用并不总是可能的，特别是在潜在的工业规模反应器应用的背景下。另一方面，直接低场NMR检测具有增强的核自旋极化的反应产物是具有挑战性的，由于从新生仲氢质子几乎完全消除信号。我们表明，通过PHIP制备的氢化产物可以用弱（几赫兹的自旋自旋耦合的量级）交变磁场（称为自旋锁定诱导交叉或SLIC）照射，因此可以在低磁场（例如，0.05本文中使用的术语“t”）使用含有乙烯基部分的几种类型的有机分子的实例。从几个反应产物中检测到的超极化信号在几十毫摩尔浓度增强了10000倍，产生的NMR信号的数量级大于质子化溶剂的背景信号。
Parahydrogen-induced polarization (PHIP) is an NMR hyperpolarization technique that increases nuclear spin polarization by orders of magnitude, and it is particularly well-suited to study hydrogenation reactions. However, the use of high-field NMR spectroscopy is not always possible, especially in the context of potential industrial-scale reactor applications. On the other hand, the direct low-field NMR detection of reaction products with enhanced nuclear spin polarization is challenging due to near complete signal cancellation from nascent parahydrogen protons. We show that hydrogenation products prepared by PHIP can be irradiated with weak (on the order of spin spin couplings of a few hertz) alternating magnetic field (called Spin-Lock Induced Crossing or SLIC) and consequently efficiently detected at low magnetic field (e.g., 0.05 T used here) using examples of several types of organic molecules containing a vinyl moiety. The detected hyperpolarized signals from several reaction products at tens of millimolar concentrations were enhanced by 10000-fold, producing NMR signals an order of magnitude greater than the background signal from protonated solvents.