title: 1H NMR relaxation in glycerol solutions of nitroxide radicals: effects of translational and rotational dynamics.
abstract: (1)H spin-lattice relaxation rates in glycerol solutions of selected nitroxide radicals at temperatures between 200 K and 400 K were measured at 15 MHz and 25 MHz. The frequency and temperature conditions were chosen in such a way that the relaxation rates go through their maximum values and are affected by neither the electron spin relaxation nor the electron-nitrogen nucleus hyperfine coupling, so that the focus could be put on the mechanisms of motion. By comparison with (1)H spin-lattice relaxation results for pure glycerol, it has been demonstrated that the inter-molecular electron spin-proton spin dipole-dipole interactions are affected not only by relative translational motion of the solvent and solute molecules, but also by their rotational dynamics as the interacting spins are displaced from the molecular centers; the eccentricity effects are usually not taken into account. The (1)H relaxation data have been decomposed into translational and rotational contributions and their relative importance as a function of frequency and temperature discussed in detail. It has been demonstrated that neglecting the rotational effects on the inter-molecular interactions leads to non-realistic conclusions regarding the translational dynamics of the paramagnetic molecules.
authors.affiliation: Faculty of Mathematics and Computer Science, University of Warmia and Mazury in Olsztyn, Sloneczna 54, PL-10710 Olsztyn, Poland. danuta.kruk@matman.uwm.edu.pl
authors.forename: D
authors.initials: D
authors.lastname: Kruk
authors.forename: A
authors.initials: A
authors.lastname: Korpala
authors.forename: E
authors.initials: E
authors.lastname: Rössler
authors.forename: K A
authors.initials: KA
authors.lastname: Earle
authors.forename: W
authors.initials: W
authors.lastname: Medycki
authors.forename: J
authors.initials: J
authors.lastname: Moscicki
mesh_terms: D005990:Glycerol / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D056004:Molecular Dynamics Simulation; D009589:Nitrogen Oxides / Q000737:chemistry*; D011522:Protons; D012399:Rotation; D012996:Solutions; D013696:Temperature
chemical_list: D009589:Nitrogen Oxides; D011522:Protons; D012996:Solutions; C039900:nitroxyl; D005990:Glycerol