Spectroscopic measurements, computational calculations, and drug assay applications of charge-transfer complexes comprising the pharmaceutical triamterene and the organic acceptors TCNQ and DDQ

Triamterene is a drug used in combination with other drugs to treat hypertension and high blood pressure. Here, we investigate the charge-transfer (CT) property of triamterene (termed as the donor) towards two strong organic electron-accepting molecules (TCNQ and DDQ). We found that the donor forms a stable, soluble deep green colored CT complex with TCNQ acceptor in acetonitrile solvent with a 1:1 molar ratio and characteristic CT band at lCT 355 nm. Furthermore, the donor forms a stable, red-colored CT complex with DDQ acceptor in methanol solvent with a 1:1 molar ratio and characteristic CT band at lCT 460 nm. IR measurements proposed a charge migration from the -NH2 of the donor molecule to the acceptor’s molecules. The two CT reactions (donor-TCNQ and donor-DDQ) were utilized to analyze the donor in pure and pharmaceutical dosage forms. The results suggest that the TCNQ and DDQ assays are appropriate for routine analysis of the donor and can be used in pharmaceutical quality control laboratories. The experimental data was justified with DFT/TD-DFT calculations using the B3LYP/6-311G++ basis set. Some important parameters of the CT complexes, along with the energy of the reaction, were also obtained. KEY WORDS: Triamterene, Charge-transfer complex, TCNQ acceptor, DDQ acceptor, Computational calculations Bull. Chem. Soc. Ethiop. 2025, 39(10), 1961-1975. DOI: https://dx.doi.org/10.4314/bcse.v39i10.7