Electronic Properties and Crystal Structure of a Methylthio Substituted Naphthalene Cation Radical Salt: (DMbTN)₃(ClO₄)₂

Abstract

The crystal structure, the conductivity, and the magnetic properties of the monoclinic cation radical salt 2,7-dimethoxy-3,6-bis(methylthio)naphthalene-perchlorate [(DMbTN),(C10,),] are presented. The stack of DMbTN molecules consists of triads which make the salt semiconducting, 4 3 0 0 K) z S/cm, with a band gap of 0.6 eV. In spite of the low conductivity the susceptibility is very high, about 0.27 spins/complex. This is due to the presence of significant correlation effects, causing the coupling between the spins to be antiferromagnetic with J = 56 meV. Because of the trimerization of the DMbTN stack the primary spin excitations are thermally activated triplet spin excitations of the Wannier type. The electrical and magnetic properties for T 5 200 K are governed by the presence of deep defect levels in the band gap. The ESR linewidth is unusually narrow, about 1 G at 300 K, for an ion-radical salt containing sulphur, this implies that the spin density on the sulphur atoms is very low.