Magnetic properties of metal–quinone high-spin complexes prepared by solid-state mechano-activation and by chemical synthesis in solution. Comparative study with very high-field and low-temperature EPR and ENDOR

Abstract

EPR spectroscopy at high frequencies and low temperatures and ENDOR spectroscopy at X- and W-bands have been applied to investigate two- and three-spin complexes of the type MQ2˙ and MQ3˙ generated by mechanochemical treatment (by grinding or by the action of elastic waves) of solid mixtures of quinones and metals (M = Al, Ga, In, Cd, Sn, Zn). In addition, complexes obtained in liquid-phase reactions of metal amalgams with quinones were investigated. The magnetic-resonance parameters and the observed thermal spin polarization provide evidence for the identity of the magnetic complexes produced in solutions and by solid-state mechanochemical treatment. In particular, the presence of ground-state triplet and quartet species has been demonstrated in both cases. In addition, the exchange and the dipole–dipole interaction parameters were evaluated, their comparison providing information about the electronic intramolecular interaction.