Field-dependent proton NMR relaxation in aqueous solutions of Ni(II) ions. A new interpretation
Field-dependent proton NMR relaxation in aqueous solutions of Ni(II) ions. A new interpretation
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DOI：
10.1006/jmra.1996.0149
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发表时间：
1996-08-01
期刊：
影响因子：
--
通讯作者：
Larsson, PT
中科院分区：
文献类型：
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作者：
Svoboda, J;Nilsson, T;Larsson, PT
提出了一个新的模型，在溶液中的顺磁性过渡金属配合物的核自旋弛豫，允许电子自旋弛豫的Redfield极限之外。新的特点是，瞬态零场分裂（ZH），调制的溶剂化壳的扭曲，被允许是菱形，而不是圆柱对称。该模型假定不存在静态电荷转移，适用于过渡金属离子的水溶液。本文研究了水溶液中质子自旋-晶格弛豫速率增强的磁场依赖性，并对S = 1的Ni ~（2+）（aq）体系，采用不同的斜方度和不同的运动条件（Redfield极限和慢运动区）进行了计算。新的模型也适用于拟合先前报道的低pH下Ni（ClO 4）（2）水溶液中质子弛豫的场依赖性数据[J. Kowalewski，T. Larsson，and P. - O. Westlund，J. Magn. Reson. 74，56（1987）]。菱形的列入，最近的理论工作的动机，提供了一个模型，以及早期的特设模型。(C)出版社：Academic Press，Inc.
A new model is presented for nuclear-spin relaxation in paramagnetic transition metal complexes in solution, allowing the electron-spin relaxation to be outside the Redfield limit. The novel feature is that the transient zero-field splitting (ZFS), modulated by distortions of the solvation shell, is allowed to be of rhombic rather than cylindrical symmetry. The model, which assumes that the static ZFS is absent, is applicable to aqueous solutions of transition metal ions. The magnetic-field dependence of the proton spin-lattice relaxation rate enhancement in aqueous solution has been investigated, and calculations are presented for an S = 1 system such as Ni2+(aq), using different degrees of rhombicity of the ZFS and different motional conditions (Redfield limit and slow-motion regime). The new model is also applied to fit the previously reported data for the field dependence of proton relaxation in aqueous solution of Ni(ClO4)(2) at low pH [J. Kowalewski, T. Larsson, and P.-O. Westlund, J. Magn. Reson. 74, 56 (1987)]. The inclusion of rhombicity, motivated by recent theoretical work, provides a model which performs as well as the earlier ad hoc model. (C) 1996 Academic Press, Inc.