Study of 7,7',8,8'-tetracyanoquinodimethane charge transfer complexes with some lone-pair-donating drugs.

The interaction between 7,7',8,8'-tetracyanoquinodimethane (TCNQ) and oxamniquine (I), azithromycin (II), omeprazole (III), pantoprazole (IV), and benzydamine hydrochloride (V) was investigated. The reaction conditions were optimized to obtain typical charge transfer complexes (CTC). The nature of the formed complexes was proved by thorough study of the thermodynamic parameters namely delta G (free energy), delta H (enthalpy), and delta S (entropy). The association constant KcAD and the molar absorptivity xi lambda AD of the formed complexes were determined using the Benesi-Hildbrand equation. The effect of temperature on these constants gave evidence of CTC formation. The reaction of TCNQ with I-V was found to be in 1:1; as being determined by the Foster method. Spectrophotometric measurements of the formed CTC were used for the quantitative determination of the studied drugs in both pure or pharmaceutical formulation. The mean percentage recoveries were 99.17 +/- 0.34, 99.75 +/- 0.12, 100.52 +/- 0.41, 98.75 +/- 0.63, and 99.23 +/- 62 for I, II, III, IV, and V, respectively. There was no significant difference observed when the method was statistically compared with the official and reference methods used to determine these drugs.