Synthesis and Spectral Analysis of Charge-Transfer Complexes of Triamterene Drug with 2,4,6-Trinitrophenol, 4-Nitrophenol, 4-Nitroacetophenone, and m-Dinitrobenzene Acceptors in the Solid-State Form: Experimental and DFT Studies

The present work aims to focus on the synthesis and spectral studies of the charge-transfer interaction between the nitro organic acceptors molecules [e.g., 2,4,6-trinitrophenol (PA), 4-nitrophenol (4-NP), 4-nitroacetophenone (4-NAP), and m-dinitrobenzene (m-DNB)] with triamterene (TM) drug donors, which have many applications in industry, biology, and chemistry. The CT complexes of PA and 4-NP are formed by the association of electrondeficient and electron-rich moieties, held together by the weak force of attraction through a hydrogen bond. These molecules have been explored through the FTIR and Raman spectroscopic techniques. The speculated 1:1 or 1:2 structures of the complexes [(TM)(PA)], [(TM)(4-NP)₂], [(TM)(4-NAP)₂], and [(TM)(m-DNB)₂] determined by microanalytical and theoretical analyses shows that the interaction occurs through a H₂N⁺–H···O−(O----H) (O–H----NH₂) bond or by n–π^* regarding 4-NAP and m-DNB complexes. The thermogravimetric technique was utilized to determine the thermostability of the synthesized charge-transfer complexes by making comparisons to their constituents. The computational study has been carried out on the studied molecule, which has the most stable conformer using density functional theory (DFT). A comparative study of electronic and vibrational spectroscopy has been done with that of experimental results. The experimentally obtained structure was compared with an optimized structure for various parameters, such as bond length, bond angles, oscillator strength, dipole moment, and molecular electrostatic potential is predicted theoretically. The energy band gap from HOMO-to-LUMO was theoretically estimated using (B3LYP/6-311++G(d,p) level) from frontier molecular orbital energies, and the outcome data are employed to characterize the chemical structures of the synthesized complexes based on molecular properties.