Growth and characterization of an efficient nonlinear optical D-π-A-π-D type chalcone single crystal

A chalcone molecule, p-methoxy dibenzylideneacetone (PDBA), with molecular formula C19H18O3 having D-pi-A-pi-D type, lambda (Lambda)-shape structure has been synthesized by Claisen-Schmidt condensation reaction. High-quality single crystals of PDBA were grown by slow evaporation solution growth technique using acetone, methanol and dimethyl formamide (DMF) as solvents. PDBA easily crystallizes in orthorhombic system with noncentrosymmetric space group, Aba2, and the cell parameters are a = 7.2756(9) angstrom, b = 33.583(6) angstrom, c = 6.132(5) angstrom and v = 1498.3 angstrom(3). The powder second harmonic generation (SHG) efficiency of PDBA was determined to be 15.5 times that of urea. This large SHG efficiency of PDBA is due to (i) the A-shape of the molecule resulting in a head-to-tail molecular columns along the crystallographic c-direction where dipole moment of the individual molecule add up to establish a net macroscopic polarization and (ii) the C-H...pi hydrogen bond interactions in PDBA crystal structure (which can extend molecular charge transfer into supramolecular realm in the exited state) which may partly contribute to the observed SHG. PDBA crystal is highly transparent in the visible to near infrared region and has lower optical cutoff of 440 nm. The thermal stability of PDBA is comparable with that of urea. High optical transparency down to blue region, better Vickers hardness value, higher powder SHG efficiency and laser damage resistance than that of urea, and the existence of phase-matching property in this chalcone make it a potential candidate for SHG applications. (C) 2008 Elsevier B.V. All rights reserved.