Thermodynamics of valence tautomeric interconversion in a tetrachlorodioxolene : cobalt 1 : 1 adduct

We report here the X-ray structure, solid state magnetic properties and temperature dependent solution electronic spectra of a 1: 1 cobalt: tetrachlorodioxolene adduct. The study showed that in the solid state this system undergoes an intramolecular electron transfer above 300 K, passing from a Co(III)-Cat charge distribution to a Co(II)-SQ one (valence tautomeric interconversion). The occurrence of this process has also been evidenced in solution by the temperature dependent electronic spectra, showing the transition to take place around 250 K. This study also provided for the first time the thermodynamic parameters of the valence tautomeric process in a 1: 1 adduct, confirming its entropy driven character. (C) 2008 Elsevier B.V. All rights reserved.