FT-IR, FT-Raman and UV spectral investigation: Computed frequency estimation analysis and electronic structure calculations on 1-bromo-2-methylnaphthalene

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 1-bromo-2-methylnaphthalene (C11H9Br) 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 density functional theory (DFT) and ab initio HF methods with different basis sets combinations. The complete vibrational assignments of wavenumbers were made on the basis of potential energy distribution (PED). The results of the calculations were applied to simulated vibrational spectra of the title compound, which show excellent agreement with observed spectra. The scaled B3LYP/6–311++G(d, p) results show the best agreement with the experimental values over the other methods. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) complements with the experimental findings. In addition, molecular electrostatic potential and nonlinear optical and thermodynamic properties of the title compound were performed. Mulliken charges and NBOs of the title molecule were also calculated and interpreted.

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► Spectroscopic properties of 1-bromo-2-methylnaphthalene were examined by FT-IR, FT-Raman techniques, HF and DFT methods.
► The complete assignments are performed on the basis of the potential energy distribution (PED).
► NLO and NBO analysis of the molecule were studied.
► HOMO and LUMO energies, Molecular electrostatic potential distribution of the molecule was calculated.