Abstract
A UV-Vis spectrophotometric method was used to confirm the intermolecular charge-transfer complexes of the drug triamterene (TM) donor with four nitro pi-acceptors (2,4,6-trinitrophenol (PA), 4-nitrophenol (4-NP), 4-nitroacetophenone (4-NAP) and m-dinirobenzene (m-DNB)) in methanol, ethanol, acetone, acetonitrile, chloroform, dichloromethane, and dichloroethane at 25 degrees C. The spectra showed chemical shifts upon the addition of TM to solutions of the nitro acceptors in the solvents. The appearance of new bands or hyper- and hypo-chromic effects confirmed the presence of charge-transfer complexes. The spectra of the complexes of TM and nitro pi-acceptors show different absorption bands at different wavelengths for different solvents. The molar ratio method showed a result of 1:1 for the TM-PA system and 1:2 for the TM-4-NP, TM-4NAP, and TM-m-DNB charge-transfer complexes. The physical spectroscopic parameters were calculated, including the formation constant (K-CT), molar extinction coefficient (epsilon(CT)), oscillator strengths (f), ionization potential (I-p), resonance energy (R-N), and Gibbs energy (Delta G degrees). The optical band gap of the TM-nitro charge-transfer complexes was estimated, and there was clearly a relationship between the different kinds of acceptors and their optical band gaps.