Spectroscopic and thermal investigations of charge-transfer complexes formed between sulfadoxine drug and different types of acceptors

Charge-transfer reactions between sulfadoxine (SDOX) as a donor with iodine (I2), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), p-chloranil (CHL) and picric acid (PA) have been studied in solid and solution forms. The stoichiometry of all complexes was found to be 1:1 by molar ratio method between donor and acceptor at a CT-band absorption bands. The data are discussed in terms of formation constant (KCT), molar extinction coefficient (εCT), standard free energy (ΔGo), 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 and UV–Vis spectroscopic techniques, Elemental analyses (CHN) and TG–DTG investigation were used to characterize the four sulfadoxine charge-transfer complexes.