Temperature Dependence of the Electrical Conductivity of Single Crystal Quinolinium (TCNQ)2

Abstract Previous electrical,(1) optical(2) and magnetic susceptibility(3) data of the complex anion-radical salt quinolinium (TCNQ)2 have been interpreted in terms of a model in which the close face to face stacking of TCNQ molecules allows the formally unpaired electron (one unpaired electron per two TCNQ molecules) to be completely delocalized over the entire TCNQ array producing a strongly degenerate electron gas. Specific evidence for this model comes from several sources: the X-ray data for other 1 : 2 complexes (e.g. triethylammonium (TCNQ)2 (4) tetraphenylphosphonium (TCNQ)2 (5)) show a face to face stacking of TCNQ with a closer than van der Waals separation between the molecular planes (no X-ray data are available for the quinolinium salt); the electrical conductivity for this complex is very high at room temperature (σ = 100 Ω−1 cm−1)l; the magnetic susceptibility is temperature independent from about 50 °K to 300 °K which has been interpreted as being due to Pauli paramagnetism(3) and the EPR ...