NMR Research Unit, Faculty of Science, University of Oulu, 90014, Finland.
Phys Chem Chem Phys. 2021 Aug 12;23(31):16542-16550. doi: 10.1039/d1cp02383g.
Laplace Nuclear Magnetic Resonance (NMR) can determine relaxation parameters and diffusion constants, giving valuable information about molecular structure and dynamics. Information about relaxation times (T1 and T2) and the self-diffusion coefficient (D) can be extracted from exponentially decaying NMR signals by performing a Laplace transform, which is a different approach to traditional NMR involving Fourier transform of a free induction decay. Ultrafast Laplace NMR uses spatial encoding to collect the entire data set in just a single scan which provides orders of magnitude time savings. In this work we use ultrafast Laplace NMR D-T2 correlation sequences to measure key relaxation (T2) and diffusion (D) parameters of methanolic solutions containing pyridine. For the first time we combine this technique with the hyperpolarisation technique Signal Amplification By Reversible Exchange (SABRE), which employs an iridium catalyst to reversibly transfer polarisation from parahydrogen, to boost the 1H NMR signals of pyridine by up to 300-fold. We demonstrate use of ultrafast Laplace NMR to monitor changes in pyridine T2 and D associated with ligation to the iridium SABRE catalyst and kinetic isotope exchange reactions. The combined 1440-fold reduction in experiment time and 300-fold 1H NMR signal enhancement allow the determination of pyridine D coefficients and T2 values at 25 mM concentrations in just 3 seconds using SABRE hyperpolarised ultrafast Laplace NMR.
拉普拉斯核磁共振（NMR）可以确定弛豫参数和扩散常数，提供有关分子结构和动力学的有价值信息。通过对指数衰减 NMR 信号进行拉普拉斯变换，可以提取弛豫时间（T1 和 T2）和自扩散系数（D）的信息，这是一种不同于传统 NMR 的方法，涉及对自由感应衰减进行傅里叶变换。超快拉普拉斯 NMR 使用空间编码仅在单次扫描中即可收集整个数据集，从而节省了数量级的时间。在这项工作中，我们使用超快拉普拉斯 NMR D-T2 相关序列来测量含吡啶的甲醇溶液的关键弛豫（T2）和扩散（D）参数。我们首次将该技术与极化增强技术 Signal Amplification By Reversible Exchange（SABRE）相结合，该技术采用铱催化剂将极化从仲氢可逆地转移到吡啶上，将吡啶的 1H NMR 信号增强高达 300 倍。我们展示了超快拉普拉斯 NMR 在监测与铱 SABRE 催化剂的配位和动力学同位素交换反应相关的吡啶 T2 和 D 的变化中的应用。实验时间缩短了 1440 倍，1H NMR 信号增强了 300 倍，使用 SABRE 极化超快拉普拉斯 NMR 仅需 3 秒即可在 25mM 浓度下测定吡啶 D 系数和 T2 值。
