Ab initio HF, DFT and experimental (FT-IR) investigation of vibrational spectroscopy of 3-(2-(4-isopropylpiperazin-1-yl)-2-oxoethyl)-6-(4-methoxybenzoyl)benzo[d]thiazol-2(3H)-one

FT-IR spectra was recorded for 3-(2-(4-isopropylpiperazin-1-yl)-2-oxoethyl)-6-(4-methoxybenzoyl)benzo[d]thiazol-2(3H)-one molecule (abbreviated as IOMBT) sample in solid state. Conformational analysis of IOMBT was performed to determine the most stable conformer. Potential energy curves of IOMBT were obtained performing a relaxed scan of D1–7 dihedral angels at B3LYP/6-311++G(d,p) level of theory. Geometrical parameters of these structures were optimized by using the same method. The molecular geometry of IOMBT was reoptimized at DFT(B3LYP) and HF methods using 6-311++G(d,p), 6-311+G(d), 6-311G(d,p), 6-311G(d) and 6-31++G(d,p) basis sets for the lowest energy conformer. The vibrational frequencies, IR intensities were calculated at DFT(B3LYP) and HF methods. The thermodynamic parameters (such as zero-point vibrational energy, EHOMO, ELUMO, thermal corrections to energy, enthalpy and Gibbs free energy, and entropy) have also been computed. The LUMO–HOMO energy gap of IOMBT shows that the energy gap reflects the chemical reactivity and the level of conductivity of the molecule.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Molecular structure was studied using HF and DFT/B3LYP methods. ► Conformational analysis were performed. ► Potential energy surfaces (PESs) were shown. ► HOMO–LUMO energies were calculated. ► The thermodynamic properties have been calculated by the theoretical vibrational analysis.