Synthesis, structural characterization and computational study of a novel amino chalcone: a potential nonlinear optical material

The interest for novel chalcone-based materials in nonlinear optics is dependent on strong second harmonic generation in organic systems. Chalcones are alpha, beta-unsaturated ketones that can be easily obtained by Claisen-Schmidt condensation between ketones and aromatic aldehydes. A new 2-amino-chalcone was synthesized and its crystal molecular structure was elucidated using the single crystal X-ray diffraction technique. This compound, C15H12BrNO2, crystallizes in monoclinic centrosymmetric space group C2/c with cell parameters a = 29.47(7) angstrom; b = 6.97(5) angstrom, c = 13.59(1) angstrom, beta = 112.52(6)degrees and V = 2581.2(2) angstrom(3) . In addition to the crystal structure, the analysis of Hirshfeld surfaces indicates the presence of hydrogen bonds of types N-H center dot center dot center dot O and O-H center dot center dot center dot O that stabilize two independent centrosymmetric dimers, and also indicates the presence of p-p stacking interactions that stabilize a supramolecular trimeric system. Being a push-pull chromophore we investigated the NLO properties of the 2-amino-chalcone asymmetric unit using the supermolecule approach in combination with an iterative electrostatic polarization scheme. The calculations were performed using the CAM-B3LYP/6-311+G(d) level of theory for both dynamic and static situations. In the presence of the embedding charges, the gamma value is increased by 20% for the dynamic calculation but only 8% for the static limit. In contrast to the crystal form, when in solution the 2-amino-chalcone lacks an inversion center so that second order NLO properties do not vanish. Following this idea we computed the NLO properties using the implicit solvation approach IEF-PCM. The solvent effect on the NLO properties was to augment its values as the solvent polarity increases. We obtained for the in-crystal and in DMSO 2-amino-chalcone, gamma(-2 omega; omega, omega, 0) = 144.12 x 10(-36) esu and 260.163 x 10(-36) esu, respectively, and therefore interesting materials for third order NLO applications.