Electronic, Raman and FT-IR spectral investigations of the charge transfer interactions between ketoconazole and povidone drugs with iodine

The interaction between ketoconazole and povidone drugs with iodine was found to proceed through initial formation of a charge transfer (CT) complex as an intermediate. The stoichiometry of the complex was found to be 1:1 in the case of povidone–iodine system and 1:2 in the case of ketoconazole–iodine system and the same was confirmed by thermal (TGA/DSC) studies. The formation of I3− species was confirmed by electronic and laser Raman spectra. The three peaks appeared in Raman spectra, of the isolated adducts corresponds to νas(I–I), νs(I–I) and δ(I3−), confirmed the presence of asymmetric I3− ion. The rate of the interaction has been measured as a function of time and solvent. The pseudo-first-order rate constants at various temperatures for the interactions were measured and the activation parameters (ΔG#, ΔS# and ΔH#) were computed. Based on the spectral and spectrokinetic evidences a mechanism involving the formation of a polar intermediate and its conversion to the final product has been proposed and discussed.