Synthesis, crystal growth and characterization of a D-π-A type novel organic nonlinear optical single crystal

A new organic nonlinear optical material 3-(4-chlorophenyl)-1-(pyridin-3-yl) prop-2-en-1-one (CPP) having high second harmonic generation efficiency has been synthesized by a Claisen-Schmidt condensation reaction method. Single crystals of CPP were grown by a slow evaporation solution growth technique. The details about the various functional groups present are obtained by FTIR, FT-Raman and 1H NMR spectroscopic studies. The single-crystal X-ray diffraction (XRD) shows that CPP crystallizes in a monoclinic crystal system with noncentrosymmetric space group P21 and the cell parameters are a=5.9339(2) Å, b=4.8881(2) Å, c=19.7804(8) Å and V=568.21(4) Å3. The second harmonic generation (SHG) efficiency of the crystal is 3.67 times that of Urea. The molecular dipoles aligned in zig-zag head to tail fashion along the crystallographic b-axis result in a net polarization and hence large SHG conversion efficiency. From UV-visible study it is found that the crystal is transparent in the entire visible region. The energy band gap of the material is found using Tauc׳s plot and by a direct method. The molecular origin of SHG efficiency is discussed in detail based on the experimental results. The position of nitrogen atom in the pyridine ring has considerable effect on the NLO response of the chalcone derivatives. The crystal is thermally stable up to 133 °C and can be used for NLO device applications.