Spectroscopic studies on the interaction of cilostazole with iodine and 2,3-dichloro-5,6-dicyanobenzoquinone.

The electron accepting properties of the 2,3-dichloro-5,6-dicyanobenzoquinone and iodine and electron donating properties of the drug cilostazole have been studied using the UV-vis, FT-IR, GC-MS and Far-IR techniques. The interaction of cilostazole drug with iodine and 2,3-dichloro-5,6-dicyanobenzoquinone resulted via the initial formation of charge-transfer complex as an intermediate. The rate of formation of the product have been measured and discussed as a function of solvent and temperature. The complexes have been found by Job's method of continuous variation revealed that the stoichiometry of the complexes in both the cases was 1:1. The enthalpies and entropies of formation of the complexes have been obtained by determining their rate constant at three different temperature. The ionization potential of the donor was determined using the charge-transfer absorption bands of the complexes and the same was found comparable with that computed using MOPAC PM3 method.