Spectral studies on the interaction of iodine with thiazoles

Abstract

The electron donor–acceptor molecular complexes between thiazole and some of its derivatives and iodine in several solvents have been investigated spectrophotometrically at different temperatures. Spectral characteristics, equilibrium constants, K, extinction coefficients, ε, and thermodynamic functions of formation, ΔH0, ΔG0, and ΔS0 have been determined. It was found that the data fit satisfactorily the 1:1 stoichiometric equilibrium: D + I2 = DI2 "outer complex". The EDA complexes obtained are of "n–σ*" type in which the nitrogen atom of thiazole is the donor center. Moreover, the effect of solvents on the K values is discussed in terms of the solute–solute and solute–solvent competing equilibria.