The highly conductive nonstoicheiometric tetrathiafulvalene nitrate: composition, conductivity, and structure

Abstract

The nonstoicheiometric tetrathiafulvalene (TTF) salt, TTF(NO₃)_0.55, has been prepared as single crystals by electrocrystallisation. At 291 K it has unidimensionally metallic properties, with a (four-probe) conductivity of 1.2 × 10³Ω^–1 cm^–1 at 291 K, along the needle axis; at < 291 K it is semiconducting. The crystals are monoclinic, space group P2₁/n, with a= 10.976, b= 11.868, c= 3.607 Å, and β= 90.79°, the nitrates are completely disordered around the centre of symmetry at (½, 0, ½) with electron density smeared along the c axis, as in other TTF adducts. Disorder of the sulphur atoms gives electron density displacements above and below the TTF plane. Electronic motion associated with TTF stacks, comprising TTF^O–TTF⁺ mixed charge entities, underlies the high c-axis conductivity.