Vibrational spectra, first hyperpolarizability, HOMO-LUMO analysis of 4-bromo 2-fluro anisole

Abstract

The FTIR and FT Raman spectra of 4-bromo-2-fluoro anisole (4B2FA) have been recorded in the regions 4000-400 and 3500-50 cm^-1, respectively. The optimized geometry, frequency and intensity of the vibrational bands of 4B2FA have been obtained by <i>ab-initio</i> and DFT levels of theory with complete relaxation in the potential energy surface using

6-311++G basis set. A complete vibrational assignment aided by the theoretical harmonic frequency analysis has been proposed. The harmonic vibrational frequencies calculated have been compared with experimental FTIR and FT Raman spectra. The observed and the calculated frequencies are found to be in good agreement. The calculated results also show that the 4-bromo-2-fluoro anisole (4B2FA) might have microscopic Non Linear Optical (NLO) behaviour with non-zero values. A detailed interpretation of the infrared and Raman spectra of 4B2FA is also reported based on total energy distribution (TED). The calculated HOMO and LUMO energy gap shows that charge transfer occur within the molecule.