Weak nuclear spin singlet relaxation mechanisms revealed by experiment and computation
Weak nuclear spin singlet relaxation mechanisms revealed by experiment and computation
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DOI：
10.1039/d1cp05537b
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发表时间：
2022-02-28
影响因子：
3.3
通讯作者：
Jerschow，Alexej
中科院分区：
文献类型：
--
作者：
Kharkov，Boris;Duan，Xueyou;Jerschow，Alexej
人们经常发现核自旋单线态可以长期存储核磁化强度，这可以构成光谱学、成像和动态过程研究中新颖应用的基础。这种极化保持完整的准确时间以及哪些因素影响其寿命通常很难确定和预测。我们提出了一项组合的实验/计算研究，以证明分子动力学模拟和从头计算可用于充分解释在氘代氯仿作为溶剂中实验观察到的 d5-丙基-d7-马来酸乙酯中的质子单线态寿命。无需调整参数即可实现实验与模拟的对应。这些研究强调了考虑不寻常且难以控制的机制的重要性，例如与低伽马溶剂核的偶极耦合，以及与残余顺磁性物质的偶极耦合，这些通常可以代表寿命限制因素。这些结果还表明了分子动力学模拟的力量，可以深入了解鲜为人知的核磁共振弛豫机制。
Nuclear spin singlet states are often found to allow long-lived storage of nuclear magnetization, which can form the basis of novel applications in spectroscopy, imaging, and in studies of dynamic processes. Precisely how long such polarization remains intact, and which factors affect its lifetime is often difficult to determine and predict. We present a combined experimental/computational study to demonstrate that molecular dynamics simulations and ab initio calculations can be used to fully account for the experimentally observed proton singlet lifetimes in ethyl-d5-propyl-d7-maleate in deuterated chloroform as solvent. The correspondence between experiment and simulations is achieved without adjustable parameters. These studies highlight the importance of considering unusual and difficult-to-control mechanisms, such as dipolar couplings to low-gamma solvent nuclei, and to residual paramagnetic species, which often can represent lifetime limiting factors. These results also point to the power of molecular dynamics simulations to provide insights into little-known NMR relaxation mechanisms.