A study of the donor properties of the phenoxachalcogenines II: 7,7,8,8-tetracyanoquinodimethane as the acceptor

Publisher Website
Google Scholar
Abstract
The phenoxachalcogenines have been studied as donors towards 7,7,8,8-tetracyanoquinodimethane. For the 1:1 complexes studied, the equilibrium constants, K, vary over the range 4–6; the enthalpy, ΔH0, is about −2.0 kcal/mol; the free energy, ΔG0, is −1.4 to −1.0 kcal/mol, and the entropy change, ΔS0, is −7.3 to −3.5 eu. The entropy change is greatest in the case of the dibenzo-1,4-dioxane – 7,7,8,8-tetracyanoquinodimethane charge-transfer complex. This is attributed to the planarity of the dibenzo-1,4-dioxane molecule. The extinction coefficient, εc, for the series studied varies from 115 to 230, and no regularity in the trend has been noted.The lack of any significant changes (with change in the chalcogen atom) in the thermodynamic values for the phenoxachalcogenine – 7,7,8,8-tetracyanoquinodimethane charge-transfer complexes is interpreted in terms of a similar π to π type interaction involving a delocalized π orbital of the phenoxachalcogenine rather than a localized n orbital of the hetero atom.The room temperature four-probe dc conductivities of single crystals of PSe–TCNQ and PS–TCNQ were found to be 4 × 10−8 and 3 × 10−7 ohm−1 cm−1, respectively.

This publication has 0 references indexed in Scilit: