Spectroscopic (FTIR, FT-Raman, NMR and UV) and molecular structure investigations of 1,5-diphenylpenta-1,4-dien-3-one: A combined experimental and theoretical study

Fourier transform infrared (FTIR) and FT-Raman spectra have been recorded and extensive spectroscopic investigations have been carried out on 1,5-diphenylpenta-1,4-dien-3-one [dibenzalacetone (DBA)]. The effects of molecular association through C-H center dot center dot center dot O hydrogen bonding have been described by the single dimer structure. The optimized geometries, wavenumber and intensity of the vibrational bands of dibenzal acetone have been calculated using density functional theory (DFr) employing B3LYP functional and 6-31G(d,p) basis set. On the basis of the comparison between calculated and experimental results assignments of the fundamental vibrational modes are examined. C-13 and H-1 NMR spectra have been recorded and C-13 and H-1 nuclear magnetic resonance chemical shifts of the molecule have been calculated using the gauge independent atomic orbital (GIAO) method. The molecular stability and bond strength have been investigated by applying the Natural Bond Orbital analysis (NBO). The electronic properties like UV spectral analysis and HOMO-LUMO analysis of DBA have been reported. Information about the size, shape, charge density distribution and site of chemical reactivity of the molecule has been obtained by mapping electron density isosurface with molecular electrostatic potential (MEP). (C) 2012 Elsevier B.V. All rights reserved.