Synthesis, structure, growth and characterization of an organic crystal: 1,5-diphenylpenta-2,4-dien-1-one

Abstract

1,5-Diphenylpenta-2,4-dien-1-one (DDO) chalcone single crystals, synthesized by a base-catalysed aldol condensation reaction between cinnamaldehyde and acetophenone, have been grown by the slow evaporation of an ethanol solution. The crystals belong to the orthorhombic system with centrosymmetric space groupPbca. The DDO crystals are transparent in the visible region and have a lower optical cut-off at ∼445 nm with a band-gap energy of 2.87 eV. Thermogravimetry/differential scanning calorimetry thermal analysis shows that the crystal is stable up to 375 K and it has a good chemical stability. The vibrational patterns of the chalcone have been investigated by Fourier transform IR and Fourier transform Raman spectroscopy. Microhardness studies were also carried out to elucidate the mechanical behaviour. Theoretical calculations were performed using the Hartree–Fock method with 6-31G(d,p) as the basis set, and the first-order hyperpolarizability is 7.077 × 10−30electrostatic units, which is >25 times that of urea. The crystalline perfection evaluated by high-resolution X-ray diffraction analysis reveals multiple peaks. The molecular packing leads to a centrosymmetric arrangement, resulting in zero second harmonic generation [χ(2)= 0] efficiency. Interestingly, the bromo- and chloro-substituted chalcones are good nonlinear optical materials.