Preparation, spectroscopic and thermal investigations on charge-transfer complexes formed in the reaction of ribavirin drug and various acceptors

Akmal S. Gaballa

Abstract

Considerable attention has recently been given to the formation of stable charge-transfer complexes that result from the reaction between drugs and acceptors due to the significant physical and chemical properties of these complexes. Charge-transfer complexes formed between ribavirin (RV) as electron donor with different electron acceptors as iodine (I2), picric acid (HPA), chloranilic acid (H2CA), and 2,3-dichloro-5,6-dicyano1,4-benzoquinone (DDQ) have been investigated in methanol at room temperature. Based on elemental analyses and IR spectra of the solid CT-complexes along with the photometric titration curves for the reactions, the stoichiometries of all complexes were found to be 1:2 molar ratio between RV and I2, and 1:1 molar ratio between RV and acceptors (HPA, H2CA, and DDQ). The infrared spectroscopic data indicate a charge transfer interaction associated with a proton migration from the acceptor to the donor followed by intramolecular hydrogen bonding in [(HRV)(PA)] and [(HRV)(HCA)] complexes. Another charge transfer interactions were observed in [(RV)I]×I3, and [(RV)(DDQ)] complexes. The characteristic physical constants (KCT, m, DG, ID, f, ECT) of the formed CT-complexes are shown to be strongly dependent on the type and structure of the electron acceptors