Charge-transfer complexes of sulfamethoxazole drug with different classes of acceptors

The charge-transfer complexes of the donor sulfamethoxazole (SZ) with iodine (I2), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), p-chloranil (CHL) and picric acid (PA) have been studied spectrophotometrically in chloroform or methanol at room temperature using absorption spectrophotometer. The results indicate that formation of CT-complexes in case of four acceptors. The stoichiometry of the complexes was found to be 1:1 ratio by molar ratio method between donor and acceptor with maximum absorption bands (CT band). The data are discussed in terms of formation constant (KCT), molar extinction coefficient (εCT), standard free energy (ΔG°), oscillator strength (ƒ), transition dipole moment (μ), resonance energy (RN) and ionization potential (ID). The results indicate that the formation constant (KCT) for the complexes were shown to be dependent upon the nature of electron acceptor, donor and polarity of solvents which were used. IR, 1H NMR, mass spectra, UV–Vis techniques, elemental analyses (CHN) and TG–DTG investigation were used to characterize the four sulfamethoxazole charge-transfer complexes.