Vibrational spectra and assignment of fundamental vibrational modes of o-bromobenzoyl chloride based on dft calulations

The molecular vibrations of O-Bromobenzoyl chloride (OBBC) were investigated in polycrystalline sample, at room temperature, by Fourier transform infrared (FT-IR) and FT-Raman spectroscopies. In parallel, ab initio and various density functional (DFT) methods were used to determine the geometrical, energetic and vibrational characteristics of OBBC. On the basis of B3LYP/6-31G* and B3LYP/6-311+G** methods and basis set combinations, a normal mode analysis was performed to assign the various fundamental frequencies according to the total energy distribution (TED). Simulation of Infrared and Raman spectra, utilizing the results of these calculations led to excellent overall agreement with observed spectral patterns. The scaled quantum mechanical (SQM) approach applying selective scaling of the DFT force fields was shown to be superior to the scaling method in its ability to ensure correct band assignments and successful simulation of IR and Raman spectra including band polarizations and intensity patterns.