Synthesis and characterization of cinnamylidene acetone – A study on tuning of band gap by vibrational spectroscopic tools

Abstract

The title molecule Cinnamylidene acetone (CA) was synthesized through a single step base catalyzed aldol type condensation between acetone and cinnamaldehyde. The prepared molecule has been characterized using NMR (1H and 13C) spectral analysis, FTIR, UV–Vis and Elemental analysis. The complete vibrational characterization of the molecule was performed using experimental (FTIR and FT-Raman) spectra and calculations at DFT level. In order to carry out a detailed vibrational spectroscopic analysis of CA, Fourier Transform Infrared and Fourier Transform Raman spectra recorded in condensed phase were used. To determine the optimized geometry and vibrational wavenumbers, Density functional theory calculations in the B3LYP/6-31G** level have been carried out followed by scaling using the scaled quantum mechanical methodology. A root mean square deviation of 6.53 cm−1 has resulted from the scaled quantum mechanical treatment. The ultraviolet visible spectra of the title compound dissolved in various solvents were recorded in the range of 300–600 nm. The natural bond orbital and frontier molecular orbital analyses were also performed using B3LYP/6-31G** method. These studies revealed a reduction in the band gap of CA in comparison with that of cinnamaldehyde (CY).