Experimental (FT-IR and FT-Raman) and theoretical (HF and DFT) investigation, IR intensity, Raman activity and frequency estimation analyses on 1-bromo-4-chlorobenzene

The FT-IR and FT-Raman spectra of 1-bromo-4-chlorobenzene (1-Br-4-CB) have been recorded using Bruker IFS 66V spectrometer in the region of 4000-100 cm−1. Ab-initio-HF (HF/6–311+G (d, p)) and DFT (B3LYP/6–31++G (d, p)/6–311++G (d, p)) calculations have been performed giving energies, optimized structures, harmonic vibrational frequencies, depolarization ratios, IR intensities, Raman activities. The vibrational frequencies are calculated and scaled values are compared with FT-IR and FT-Raman experimental values. Comparison of simulated spectra with the experimental spectra provides important information, the computational method have the ability to describe the vibrational methods. The frequency estimation analysis on HF and DFT is made. The impact of di-substituted halogens on the benzene molecule has also been discussed.

Graphical abstractThe FT-IR and FT-Raman spectra of 1-bromo-4-chlorobenzene (1-Br-4-CB) have been recorded using Bruker IFS 66V spectrometer in the region of 4000–100 cm−1. Ab-initio-HF (HF/6–311+G (d, p)) and DFT (B3LYP/6–31+/6–311++G (d, p)) calculations have been performed giving energies, optimized structures, harmonic vibrational frequencies, depolarization ratios, IR intensities, Raman activities. The vibrational frequencies are calculated and scaled values are compared with FT-IR and FT-Raman experimental values. Comparison of simulated spectra with the experimental spectra provides important information, the computational method have the ability to describe the vibrational methods. The frequency estimation analysis on HF and DFT is made. The impact of di-substituted halogens on the benzene molecule has also been discussed.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Ab-initio-HF (HF/6–311+G (d, p)) and DFT (B3LYP/6–31+/6–311++G) calculations have been performed giving energies, optimized structures, harmonic vibrational frequencies, depolarization ratios, IR intensities, Raman activities. ► The FT-IR and FT-Raman spectra of the 1-Br-4-CB are recorded in Bruker IFS 66V spectrometer in the range of 4000–100 cm−1. ► The molecular structure of the title compound in the ground state is computed both ab-initio-HF with 6–311+G (d, p) and DFT (B3LYP) with 6–311++G (d, p) and 6–31++G (d, p) basis sets. ► The distortion of ring structure due to the substitutions is discussed related to the experimental data. ► Computed vibrational spectral IR intensities and Raman activities of the 1-Br-4-CB for corresponding wave numbers by HF and DFT methods with B3LYP at 6–311++G (d, p) basis sets have been discussed. ► The standard deviation (SD) calculation made between experimental and computed frequencies (HF/DFT) for the 1-Br-4-CB is presented. ► The ideal estimation of frequencies by DFT (B3LYP) method is presented.