Correlation of thermodynamic stabilities of charge transfer complexes of anthracene and chloranil with those of tetra-cyanoethylene

Abstract

The formation constants of charge-transfer complexes of a number of 9- and 9,10-substituted anthracenes with chloranil have been measured by a spectrophotometric method and the corresponding thermodynamic parameters ΔG° c, ΔH° c and ΔS° c evaluated in various solvents. v max values of the chargetransfer band for chloranil were linearly related to those for tetracyanoethylene (TCNE). Good correlations were also obtained between v max and the corresponding ionisation potentials Ip of the donor molecules. In addition ΔG° c varied linearly with Ip and from these correlations, values of ΔG° c, etc. for the corresponding TCNE complexes could be calculated. These values are otherwise very difficult to obtain due to the high reactivity of TCNE.