Kowalewski J, Egorov A, Kruk D, Laaksonen A, Nikkhou Aski S, Parigi G, Westlund P-O
Department of Physical, Inorganic and Structural Chemistry, Stockholm University, Arrhenius Laboratory, S-106 91 Stockholm, Sweden.
J Magn Reson. 2008 Nov;195(1):103-11. doi: 10.1016/j.jmr.2008.08.011. Epub 2008 Aug 30.
Aqueous solutions of simple nickel(II) salts are a classical test case for theories of the paramagnetic relaxation enhancement (PRE) and its dependence on the magnetic field (nuclear magnetic relaxation dispersion, NMRD), going back to late fifties. We present here new experimental data, extending the NMRD range up to 21T (900 MHz). In addition to salt solutions in (acidified) water, we have also measured on solutions containing glycerol. The aqueous solution data do not show any significant changes compared to the earlier experiments. The interpretation, based on the general ("slow-motion") theory is also similar to the earlier work from our laboratory. The NMRD-data in mixed solvents are qualitatively different, indicating that the glycerol not only changes the solution viscosity, but may also enter the first coordination sphere of the metal ion, resulting in lower symmetry complexes, characterized by non-vanishing averaged zero-field splitting. This hypothesis is corroborated by molecular dynamics simulations. A strategy appropriate for interpreting the NMRD-data for the chemically complicated systems of this type is proposed.
简单镍（II）盐的水溶液是顺磁弛豫增强（PRE）理论及其对磁场依赖性（核磁共振弛豫色散，NMRD）的经典测试案例，这可以追溯到五十年代后期。我们在此展示新的实验数据，将NMRD范围扩展至21T（900 MHz）。除了（酸化）水中的盐溶液，我们还测量了含甘油的溶液。与早期实验相比，水溶液数据未显示出任何显著变化。基于一般（“慢运动”）理论的解释也与我们实验室早期的工作相似。混合溶剂中的NMRD数据在性质上有所不同，这表明甘油不仅改变了溶液粘度，还可能进入金属离子的第一配位层，从而形成对称性较低的配合物，其特征是平均零场分裂不为零。分子动力学模拟证实了这一假设。本文提出了一种适用于解释此类化学复杂体系NMRD数据的策略。
