Solvent and temperature effects in the electron spin resonance spectrum of the hexamethylacetone-sodium ion-quartet

The sodium coupling constant of the radical obtained by reduction of hexamethylacetone in tetrahydrofuran, methyltetrahydrofuran and their binary mixtures has been studied as a function of solvent composition and temperature. The solvent dependence of the sodium coupling constant may be explained by a simple model involving equilibria between radicals differing only in the composition of the solvent sheath. The increase of the sodium coupling constant on cooling the solution may be caused by structural changes in the solvent sheath and a depopulation of vibrational levels.