Dephasing of electron spin echoes for nitroxyl radicals in glassy solvents by non-methyl and methyl protons

Molecular dynamics of nitroxides in glasses as studied by multi-frequency EPR

“…In the present article, relaxation that depends on the resonance position in the ED-EPR spectrum is called anisotropic, whereas relaxation that is uniform over the whole spectrum is called isotropic. By measuring the S120 E. P. Kirilina et al transverse relaxation rates at different resonance positions and thereby selecting different orientations of the spin probe, these processes can be characterized and, moreover, discriminated from orientation-independent relaxation mechanisms such as methyl group rotation 14,19 and nuclear spin dynamics. 12,14,20 In frozen solution, orientation-dependent relaxation may be induced by the collective motion of the solvent cage, 13 reorientational molecular motion within the cage 21 or dynamic A-and g-strains.…”

“…By measuring the S120 E. P. Kirilina et al transverse relaxation rates at different resonance positions and thereby selecting different orientations of the spin probe, these processes can be characterized and, moreover, discriminated from orientation-independent relaxation mechanisms such as methyl group rotation 14,19 and nuclear spin dynamics. 12,14,20 In frozen solution, orientation-dependent relaxation may be induced by the collective motion of the solvent cage, 13 reorientational molecular motion within the cage 21 or dynamic A-and g-strains. 22 In recent ED-EPR studies, it was shown that far below the glass transition temperature T g , fast restricted motion (¾10 9 s) dominates the anisotropic relaxation.…”

Electron spin-lattice relaxation in solid ethanol: Effect of nitroxyl radical hydrogen bonding and matrix disorder

“…The strong impact of hydrogen bonding between the dopant molecule and ethanol host on the spin relaxation was observed in ethanol glass whereas in crystalline ethanol both paramagnetic guest molecules behaved similarly. DOI: 10.1103/PhysRevB.80.052201 PACS number͑s͒: 61.43.Fs, 76.30.Ϫv, 63.50.Ϫx, 65.60.ϩa Coupling of the electron spin to disorder modes of various doped matrices has been extensively studied due to the sensitivity of the approach toward dynamical properties of the observed systems.1-3 Research on disordered solids has shown that nitroxyl radicals can contribute toward the characterization of glass-forming materials, 4-6 providing experimental data for the development of self-consistent theories of molecular dynamics in glasses in general.7-10 The work presented here has been in part motivated by the lack of nitroxyl spin-lattice relaxation-time data measured below 20 K in disordered solids 11,12 and, to the best of the authors' knowledge, by the very few examples comparing paramagnetic relaxation rate data in glassy and crystalline states of the same compound. 13 Solid ethanol has been found to be a very convenient model system for the investigation of molecular solids, as it can be easily prepared in phases characterized by different types of disorder.…”

“…[1][2][3] Research on disordered solids has shown that nitroxyl radicals can contribute toward the characterization of glass-forming materials, [4][5][6] providing experimental data for the development of self-consistent theories of molecular dynamics in glasses in general. [7][8][9][10] The work presented here has been in part motivated by the lack of nitroxyl spin-lattice relaxation-time data measured below 20 K in disordered solids 11,12 and, to the best of the authors' knowledge, by the very few examples comparing paramagnetic relaxation rate data in glassy and crystalline states of the same compound. 13 Solid ethanol has been found to be a very convenient model system for the investigation of molecular solids, as it can be easily prepared in phases characterized by different types of disorder.…”

“…7-10 The work presented here has been in part motivated by the lack of nitroxyl spin-lattice relaxation-time data measured below 20 K in disordered solids 11,12 and, to the best of the authors' knowledge, by the very few examples comparing paramagnetic relaxation rate data in glassy and crystalline states of the same compound. 13 Solid ethanol has been found to be a very convenient model system for the investigation of molecular solids, as it can be easily prepared in phases characterized by different types of disorder.…”