ELECTRONIC-PROPERTIES AND CRYSTAL-STRUCTURE OF A METHYLTHIO SUBSTITUTED NAPHTHALENE CATION RADICAL SALT - (DMBTN)3(CLO4)2

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)3(ClO4)2] are presented. The stack of DMbTN molecules consists of triads which make the salt semiconducting, σ(300 K) ≈ 10−4 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 ⪅ 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. Copyright © 1990 WILEY‐VCH Verlag GmbH & Co. KGaA