Institute of Physics, Jagiellonian University, Reymonta 4, PL-30-059 Krakow, Poland.
J Chem Phys. 2011 Jan 14;134(2):024508. doi: 10.1063/1.3516590.
The "Swedish slow motion theory" [Nilsson and Kowalewski, J. Magn. Reson. 146, 345 (2000)] applied so far to Nuclear Magnetic Relaxation Dispersion (NMRD) profiles for solutions of transition metal ion complexes has been extended to ESR spectral analysis, including in addition g-tensor anisotropy effects. The extended theory has been applied to interpret in a consistent way (within one set of parameters) NMRD profiles and ESR spectra at 95 and 237 GHz for two Gd(III) complexes denoted as P760 and P792 (hydrophilic derivatives of DOTA-Gd, with molecular masses of 5.6 and 6.5 kDa, respectively). The goal is to verify the applicability of the commonly used pseudorotational model of the transient zero field splitting (ZFS). According to this model the transient ZFS is described by a tensor of a constant amplitude, defined in its own principal axes system, which changes its orientation with respect to the laboratory frame according to the isotropic diffusion equation with a characteristic time constant (correlation time) reflecting the time scale of the distortional motion. This unified interpretation of the ESR and NMRD leads to reasonable agreement with the experimental data, indicating that the pseudorotational model indeed captures the essential features of the electron spin dynamics.
迄今为止，应用于过渡金属离子配合物溶液的核磁共振弛豫分散（NMRD）谱的“瑞典慢动作理论”[Nilsson 和 Kowalewski，J. Magn. Reson. 146, 345 (2000)]已扩展到电子顺磁共振（ESR）光谱分析，包括外加 g 张量各向异性效应。扩展后的理论已应用于以一致的方式（在一组参数内）解释 NMRD 谱和 95 和 237 GHz 下的 ESR 光谱，用于两个 Gd(III)配合物，分别表示为 P760 和 P792（DOTA-Gd 的亲水衍生物，分子量分别为 5.6 和 6.5 kDa）。目的是验证常用的瞬态零场分裂（ZFS）拟旋转模型的适用性。根据该模型，瞬态 ZFS 由具有恒定幅度的张量描述，在其自身的主轴系统中定义，该张量根据各向同性扩散方程根据特征时间常数（相关时间）改变其相对于实验室框架的取向，该特征时间常数反映了畸变运动的时间尺度。ESR 和 NMRD 的这种统一解释与实验数据合理一致，表明拟旋转模型确实捕获了电子自旋动力学的基本特征。
