Enthalpies of sublimation and vapor pressures of 2,2′-bis-1,3-dithiole (TTF), 7,7,8,8-tetracyanoquinodimethane (TCNQ), and TTF–TCNQ (1:1)

Abstract

Torsion and mass loss effusion techniques are applied simultaneously to measure the saturation vapor pressures as a function of temperature. The enthalpies of sublimation are derived from the temperature dependence of vapor pressure. Overall mean values for both techniques are: TTF, ΔH0(344.91 K) = (95.3±1) kJ mol−1; TCNQ, ΔH0(431.74 K) = (126.1±1) kJ mol−1; TTF–TCNQ(1:1), ΔH0(410.65 K) = (130.0±2) kJ mol−1. The temperatures given are midrange values at which the saturation vapor pressure of each sample is 0.4 Pa. It is shown that the TTF–TCNQ sample evaporates stoichiometrically but not as a complex.