Solid-state characterisation of the 7,7,8,8-tetracyano-p-quinodimethanide salt of the 5,5-dimethyldibenzophospholium cation

Abstract

The electrical conductivity, magnetic susceptibility and i.r. and u.v. spectra of (5,5-dimethyldibenzophospholium)⁺(7,7,8,8-tetracyano-p-quinodimethanide)^–₂, DMDBP–TCNQ₂, are reported. The conductivity is anisotropic, with σ_{300 K}= 5 × 10^–4, 2 × 10^–4 and 3 × 10^–3 S cm^–1 along a, b and c, respectively, and in the TCNQ stacking direction the conductivity varies as σ=σ₀ exp (–E_a/kT), where E_a= 0.20 eV. The paramagnetic susceptibility is activated with J= 0.007 eV. The infrared spectrum of DMDBP–TCNQ₂ shows two main features: (i) a broad electronic absorption and (ii) a series of relatively narrow lines which may be regarded as a consequence of electron–phonon coupling. Two models are proposed which adequately describe the properties.