Joint analysis of ESR lineshapes and 1H NMRD profiles of DOTA-Gd derivatives by means of the slow motion theory

Abstract

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.

Zero-field splitting in nickel(II) complexes: A comparison of DFT and multi-configurational wavefunction calculations

“…On the other hand, it is certainly interesting to review comparisons between the ab initio and DFT calculations for mononuclear complexes of other transition metal ions. Maganas and co-workers 29 investigated the capabilities of the two approaches in the case of some four-coordinated high-spin Co(II) (d 7 , S = 3/2) complexes. The ZFS was found to be dominated by the SOC.…”

“…4 Finally, it is possible to estimate the ZFS in an indirect, model-dependent way, by measuring the NMR relaxation rates for nuclear spins residing in a ligand bound to the paramagnetic centre. 6,7 All these methods make use of the spin Hamiltonian formulation, including the ZFS term …”

Nuclear quadrupole resonance lineshape analysis for different motional models: Stochastic Liouville approach

“…31 Recently this treatment has been adapted to ESR lineshape analysis, resulting in a complete tool for describing jointly the nuclear spin relaxation in paramagnetic systems and the ESR lineshape for arbitrary motional conditions. 32 The first application of the slow motion theory to quadrupole systems (systems including nuclei possessing quadrupole moments) is the work of Westlund and Wennerström 33 describing the nuclear spin-lattice relaxation of a spin 1/2 nucleus caused by a dipole-dipole coupling to neighboring quadrupole nuclei with S = 1. This treatment has been followed by further work for S = 1.…”

Forty Years of the d1/d Parameter

“…The unified interpretation of the EPR and NMRD leads to reasonable agreement with the experimental data. Seems, this approach to the electron spin dynamics can be also effectively used for quantitative description in the case of nitroxide spin probes and labels (Kruk et al, 2011).…”

“…The first article considers joint analysis of EPR line shapes and 1 H nuclear magnetic relaxation dispersion (NMRD) profiles of DOTA-Gd derivatives by means of the slow motion theory (Kruk et al, 2011). NMRD profiles have been extended to ESR spectral analysis, including in addition g-tensor anisotropy effects.…”