Spin mixing at level anti-crossings in the rotating frame makes high-field SABRE feasible
Spin mixing at level anti-crossings in the rotating frame makes high-field SABRE feasible
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DOI：
10.1039/c4cp03765k
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发表时间：
2014-01-01
影响因子：
3.3
通讯作者：
Ivanov, Konstantin L.
中科院分区：
文献类型：
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作者：
Pravdivtsev, Andrey N.;Yurkovskaya, Alexandra V.;Ivanov, Konstantin L.
提出了一种在高磁场下进行可逆交换信号放大（SABRE）实验的新技术。 SABRE 是一种利用合适的催化剂，在瞬态复合物中利用从仲氢到基底自旋的自旋顺序转移的方法。这种自旋顺序的转移在低磁场下是有效的，特别是在能级反交叉（LAC）区域。这里证明了在射频场作用下旋转参考系中的高场也可以满足 LAC 条件。 LAC 中的旋转混合也允许在高场下极化基板；对于用作底物的部分氘代吡啶的邻位质子，可实现的 NMR 增强约为 360；对于 H-2 和与催化剂的活性络合物中的底物，可实现的 NMR 增强约为 700。芳香环中含有氮原子的其他几种分子也发现了高场 SABRE 效应。
A new technique is proposed to carry out Signal Amplification By Reversible Exchange (SABRE) experiments at high magnetic fields. SABRE is amethod, which utilizes spin order transfer from para-hydrogen to the spins of a substrate in transient complexes using suitable catalysts. Such a transfer of spin order is efficient at low magnetic fields, notably, in the Level Anti-Crossing (LAC) regions. Here it is demonstrated that LAC conditions can also be fulfilled at high fields in the rotating reference frame under the action of an RF-field. Spin mixing at LACs allows one to polarize substrates at high fields as well; the achievable NMR enhancements are around 360 for the ortho-protons of partially deuterated pyridine used as a substrate and around 700 for H-2 and substrate in the active complex with the catalyst. High-field SABRE effects have also been found for several other molecules containing a nitrogen atom in the aromatic ring.