In Situ Spectrophotometric Investigation of Charge Transfer Complexes Between Triamterene, a Management of Hypertension Drug, and Four Kinds of Nitro Acceptors in Different Organic Solvents

Abstract

A UV–Vis spectrophotometric method was used to confirm the intermolecular charge-transfer complexes of the drug triamterene (TM) donor with four nitro π-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 °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 π-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 (KCT), molar extinction coefficient (εCT), oscillator strengths (f), ionization potential (Ip), resonance energy (RN), and Gibbs energy (ΔG°). 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.