Spectroscopic studies of charge transfer complexes between colchicine and some pi acceptors.

Charge transfer complexes between colchicine as donor and pi acceptors such as tetracyanoethylene (TCNE), 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), p-chloranil (p-CHL) have been studied spectrophotometrically in dichloromethane at 21 degrees C. The stoichiometry of the complexes was found to be 1:1 ratio by the Job method between donor and acceptors with the maximum absorption band at a wavelength of 535, 585 and 515 nm. The equilibrium constant and thermodynamic parameters of the complexes were determined by Benesi-Hildebrand and van't Hoff equations. Colchicine in pure form and in dosage form was applied in this study. The formation constants for the complexes were shown to be dependent on the structure of the electron acceptors used.

Charge transfer complex studies between some non-steroidal anti-inflammatory drugs and pi-electron acceptors.

Charge transfer (CT) complexes of some non-steroidal anti-inflammatory drugs, naproxen and etodolac which are electron donors with some pi-acceptors, such as tetracyanoethylene (TCNE), 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), p-chloranil (p-CHL), have been investigated spectrophotometrically in chloroform at 21 degrees C. The coloured products are measured spectrophotometrically at different wavelength depending on the electronic transition between donors and acceptors. Beer's law is obeyed and colours were produced in non-aqueous media. All complexes were stable at least 2 h except for etodolac with DDQ stable for 5 min. The equilibrium constants of the CT complexes were determined by the Benesi-Hildebrand equation. The thermodynamic parameters DeltaH, DeltaS, DeltaG degrees were calculated by Van't Hoff equation. Stochiometries of the complexes formed between donors and acceptors were defined by the Job's method of the continuous variation and found in 1:1 complexation with donor and acceptor at the maximum absorption bands in all cases.