Triplet spin excitons, structure and conductivity of (TMN)3(AsF 6)2 and (TMN)3(ClO4)2 , the radical cation salts of tetramethoxynaphthalene

Abstract

The 3:2 stoichiometry of the (TMN) 3 (ASF 6 ) 2 salt is reflected in an alternating stack configuration with TMN-triads resulting in a diamagnetic ground state. Triplet spin excitons are accessible with activation energies of 0.19 eV (AsF 6 ) and 0.28 eV (ClO 4 ). The respective fine structure parameters are D=±0.00667 cm −1 , E=∓0.00117 cm −1 and D=±0.00829 cm −1 , E=∓0.00090 cm −1 . Spin exchange leads to line narrowing at higher temperatures. The conductivity is quite low (σ(300 K)∼10 −4 Ω u − 1 cm −1 (TMN) 3 (AsF 6 ) 2 ) and may result from charge carriers, thermally activated from defect states and across the band gap, respectively Mesures de conductivite electrique et analyse des spectres RPE de ce sel a configuration empilee avec des groupes de 3 TWN, conduisant a un etat fondamental diamagnetique. Energies d'activation des excitons triplets. Parametres de structure fine. Retrecissement des raies RPE par echange de spin, a haute temperature. Conductivite electrique tres faible, qui pourrait resulter de porteurs de charge actives thermiquement a partir d'etats de defauts et a travers la bande interdite respectivement