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The present study aimed to analyze the solute–solvent interactions of indapamide using FT-IR, UV–Vis spectroscopies in combination with DFT calculations in four different solvents. The FT-IR spectra of indapamide and solutions of indapamide prepared in ethanol, in methanol, in THF and in DMSO were recorded. The theoretical analysis of probable stable conformers of indapamide was carried out using DFT/B3LYP functional with 6-31G (d,p), 6-311 G ++ (d,p) and plus D3 empirical dispersion function with 6-311 ++G(d,p) basis sets in different media. The optimized geometry and vibrational wavenumbers of indapamide were calculated using DFT method at the same level. Solvent effects of indapamide were performed with conductor-like polarizable continuum model (CPCM) method. The electronic absorption spectra of the molecule were estimated by the time-dependent DFT method at the same level. Solute–solvent interactions are investigated by means of the multi-component linear regression analysis of Kamlet–Taft parameters. Also in this study, the solvent-accessible surface area (SASA) and HOMO–LUMO energy gap were calculated using the quantum chemical calculations.

1,3-bis(benzimidazol-2-yl)-2-thiapropane (L) ligand and its zinc halide ZnX2 (X = Cl, Br, I) complexes have been synthesized. The compounds were characterized using the elemental analysis, molar conductivity, FT-Raman, FT-IR (mid i.r., far i.r.), 1H and 13C NMR spectra, and quantum chemical calculations performed with Gaussian 03 package program set. The optimized geometries and vibrational frequencies of the ligand and [Zn(L)Cl2] complex were calculated using the DFT/B3LYP method with a 6–31g(d) basis set. The geometry optimization of [Zn(L)Cl2] yields a slightly distorted tetrahedral environment around Zn ion, while the molecule clearly reveals the Cs symmetry. The molar conductivity data reveals that the complexes are neutral. The ligand is bidentate, via two of the imine nitrogen atoms in the bis-imidazole ring units, and together with the monodentate coordination of the two halides to the metal centre.