Synthesis, spectroscopic and thermodynamic study of charge transfer complexes of natural drug rutin as donor with Π-acceptors; 2,3-dichloro-5,6-dicyano-1,4-benzoquinone and tetracyanoethylene

Abstract

Molecular charge-transfer complexes of the donor rutin with π-acceptors tetracyanoethylene (TCNE) and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) were studied spectrophotometrically in two different solvents (methanol and ethanol) at three temperatures, 15, 20 and 25 °C . Formed complexes exhibit well resolved charge-transfer bands in the regions where neither donor nor acceptors have any absorption. the composition of the CTC were determined using molar ratio method and Benesi-Hildbrand equation was used to calculate the formation constants KCT and the molar extinction coefficient ɛCT of the formed CT complexes. Solid CTC were characterized by FT-IR and NMR spectroscopy. CT complexes formed in the reaction of rutin and π-acceptors DDQ and TCNE have high formation constants KCT indicating the high stability of these complexes. The latter was found to be influenced by the solvent nature, indeed, KCT values of [rut-DDQ] complex formed in ethanol are higher than those of the same complex formed in methanol, but KCT values of [rut-TCNE] complex formed in methanol are higher than those of the same complex formed in ethanol. Our results suggest the formation of stable CT complexes of rutin with π-acceptors (DDQ and TCNE).