New conducting radical salts based upon Keggin-type polyoxometalates and perylene

Abstract

Three new radical salts, Per₆[PMo₁₂O₄₀]·CH₂Cl₂ (1), Per₆[PMo₁₂O₄₀]·CH₃CN (2), and Per₉(NBu₄)₄[SiW₁₂O₄₀]₂ (3) (Per = perylene), have been synthesised and their electrical and magnetic properties characterised. These three salts are diamagnetic and they behave as semiconductors with room temperature conductivities of 69, 3.6 and 0.85 S cm⁻¹. While salt 2 presents hole-type conduction and 3 exhibits electron-dominated electrical transport properties, salt 1 shows at 150 K an abrupt change in the thermal dependence of the electrical conductivity and the Seebeck coefficient suggesting a phase transition.