Quantum chemical studies on structure of 1-3-dibromo-5-chlorobenzene

Molecular structure and vibrational frequencies of 1-3-dibromo-5-chlorobenzene (DBCB) have been investigated by density functional theory (DFT) calculations using Becke's three-parameter exchange functional combined with Lee–Yang–Parr correlation (B3LYP) and standard basis set 6-31G. DFT (B3LYP/6-31G) calculations have been performed giving energies, optimized structure, harmonic vibrational frequencies, IR intensities, and Raman activities. Raman and IR spectra of the DBCB were recorded and complete assignment of the observed vibrational bands of DBCB has been proposed. The predicted first-hyperpolarizability of DBCB is 1.221 × 10−30 esu, which suggests that the title compound is an attractive object for future studies of non-linear optical properties. The impact of di-substituted halogens on the compound has also been discussed. Besides, molecular electrostatic potential (MEP), HOMO–LUMO analysis and NBO analysis were performed at DFT level of theory The UV–vis spectral analysis of DBCB has also been done which confirms the charge transfer of the title compound.

Graphical abstractMolecular structure and vibrational frequencies of 1-3-dibromo-5-chlorobenzene (DBCB) have been investigated by density functional theory (DFT) calculations using Becke's three-parameter exchange functional combined with Lee–Yang–Parr correlation (B3LYP) and standard basis set 6-31G. Raman and IR spectra of the DBCB were recorded and complete assignment of the observed vibrational bands of DBCB has been proposed. The HOMO–LUMO analysis explains the charge transfer within the molecule. The UV–vis spectral analysis of DBCB has also been done which confirms the charge transfer of the title molecule. The predicted first-hyperpolarizability of DBCB is 0.8331 × 10−30 esu, which suggests that the title molecule is an attractive object for future studies of non-linear optical properties. The NBO analysis has been done in order to explain the interaction between electron donors and acceptors.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► HOMO and LUMO energy gap explains the eventual charge transfer within the molecule. ► NBO study reveals that lone pair orbital participates in electron donation. ► NMR study explains chemical shift of 1H and 13C of the title molecule. ► NLO property has been observed by predicting the first hyperpolarizability. ► MEP study shows that the electrophilic attack takes place at the Cl7 position.