Analysis of charge-transfer complexes caused by the interaction of the antihypertensive drug valsartan with several acceptors in CH2Cl2 and CHCl3 solvents and correlations between their spectroscopic parameters

Abstract

The charge-transfer (CT) interaction of the widely used antihypertensive drug valsartan (Val) with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), tetrafluoro-1,4-benzoquinone (TFQ), and 7,7,8,8-tetracyanoquinodimethane (TCNQ) resulted in new CT complexes [(Val)(DDQ)], [(Val)(TFQ)], and [(Val)(TCNQ)] that were characterized by Fourier transform infrared (FTIR) and ultraviolet–visible (UV/Vis) spectroscopies. The CT complexes were prepared in two non-polar solvents: dichloromethane (CH2Cl2) and trichloromethane (CHCl3) at room temperature. Val reacted with the acceptors via a 1:1 M ratio by donation electrons from Val's biphenyl rings to the aromatic ring of the acceptor (π → π* interaction). Spectral results and the Benesi-Hildebrand approach were used to estimate the following spectroscopic parameters for the newly generated CT complexes: molar absorptivity (εmax), association constant (KCT), energies parameters [ionization potential (IP), interaction energy (ECT), standard free energy change (ΔG°), and resonance energy (RN)], transition dipole moment (μ), and oscillator strength (f). Statistical analyses indicated a strong correlation among several of these spectroscopic parameters.