Study of Charge Transfer Complexes of Salicylideneanilines and its Substituents with Pr(fod)3 in Cyclohexane by U.V. Spectroscopy

Salicylidene aniline and its substituents form 1:1 charge transfer complexes with the lanthanide shift reagent Pr(fod)3 in cyclohexane indicated by the observation of a new band in their U.V. spectra located at longer wavelength (max = 430 nm) and with its low extinction coefficient. The colourless solutions of Schiffs-bases were changed to yellow on complexation with Pr(fod)3.
Equilibrium constant values (K) for the complexes were calculated by applying Benesi-Hildebrand equation at different temperatures, and the thermodynamic parameters H, S and G were obtained. Negative values of G indicates that the complexation occurs spontaneously.
Application of Hammet equation on K values for the para substituents show straight line with negative slope indicating that the electron donating groups enhances the reaction of complexation.