FT-IR, FT-Raman and UV spectral investigation: Computed frequency estimation analysis and electronic structure calculations on chlorobenzene using HF and DFT

In this work, the vibrational spectral analysis was carried out by using FT-Raman and FT-IR spectroscopy in the range 100–4000 cm−1 and 400–4000 cm−1 respectively, for the title molecule. The molecular structure, fundamental vibrational frequencies and intensity of the vibrational bands are interpreted with the aid of structure optimizations and normal coordinate force field calculations based on Hartree Fock (HF) and density functional theory (DFT) method and different basis sets combination. The complete vibrational assignments of wavenumbers were made on the basis of potential energy distribution (PED). The scaled B3LYP/6-311++G(d,p) results show the best agreement with the experimental values over the other methods. The effects due to the substitution of halogen bond were investigated. The results of the calculations were applied to simulated spectra of the title compound, which show excellent agreement with observed spectra. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) results complements with the experimental findings. Besides, frontier molecular orbitals (FMO), molecular electrostatic potential (MEP), and thermodynamic properties were performed. The thermodynamic properties of the title compound at different temperatures have been calculated, revealing the correlations between heat capacity (C), entropy (S), and enthalpy changes (H) and temperatures.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Molecular structure of chlorobenzene molecule was studied using HF and DFT/B3LYP. ► The complete assignments are performed on the basis of the total energy distribution (TED). ► All results were compared with experimental (FT-IR, FT-Raman and UV) spectra. ► Molecular electrostatic potential (MEP), electrostatic potential (ESP), electron density (ED) distribution of chlorobenzene were calculated.