Experimental Spectroscopic (FT-IR, FT-Raman, NMR) and DFT Studies of 7-methoxy-4-bromomethylcoumarin

The vibrational fundamental modes of 7-methoxy4-bromomethylcoumarin (7BMC) have been analyzed by combining FTIR, FT-Raman and quantum chemical calculations. The structural parameters of the compound are determined from the optimized geometry by B3LYP method with 6-311++G (d, p) basis set. The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FTIR and FT-Raman spectra. 1H and 13C NMR spectra have been analyzed and 1H and 13C nuclear magnetic resonance chemical shifts are calculated using the gauge independent atomic orbital (GIAO) method. The theoretical UV–VIS spectrum of the compound and the electronic properties, such as HOMO (highest occupied molecular orbital) and LUMO (lowest occupied molecular orbital) energies were performed by time-dependent density functional theory (TD-DFT) approach. Information about the size, shape, charge density distribution and site of chemical reactivity of the molecule have been obtained by mapping electron density isosurface with molecular electrostatic potential (MESP). The change in electron density (ED) in the * antibonding orbitals and stabilization energies E(2) have been calculated by natural bond (NBO) analysis to give clear evidence of stabilization originating in the hyper conjugation of hydrogen–bonded interactions.