Electron Spin Relaxation in the N,N′-Dimethylpyrazine Cation Radical

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Abstract
Line shapes in the ESR spectrum of the N,N′‐dimethylpyrazine cation radical have been studied from 20° to −80°C, and an analysis has been carried out using the relaxation matrix theory. It turns out that anisotropic dipole and g‐tensor interactions provide the major relaxation mechanisms. Classical dipole tensor components have been calculated for all of the magnetic nuclei, and it is shown that the hyperfine splitting constants for the nitrogen nuclei and the methyl protons are positive. Partially resolved second‐order structure is observed in some of the lines and a linewidth correction has been introduced to take this into account. Spin relaxation resulting from modulation of the isotropic dipole interactions through contact with the counter ion is discussed on the basis of an electrostatic model and a steric model. The predictions of the steric model are the most acceptable, but neither has been confirmed experimentally.