Intermolecular Interactions and Second-Harmonic Generation Properties of (E)‑1,5-Diarylpentenyn-1-ones

Investigation of crystal structures of eight quasi-planar (E)-1,5-diarylpentenyn-1-ones has been carried out. Five of these compounds crystallize in chiral space groups. Intermolecular interactions responsible for the loss of planarity and steric hindrances that prevent molecules to form centrosymmetric dimers were suggested to be the reasons of the crystallization in chiral groups. Intermolecular bonding has been investigated by means of the Hirshfeld surfaces, and the role of the C–H···O interactions as driving force for crystal structure formation has been demonstrated. Three types of C–H···O bonded synthons have been suggested for this family. Those synthones are found to be in accordance with the charge distribution along the conjugated system estimated with natural population analysis. Nonlinear optical (NLO) properties for five (E)-1,5-diarylpent-2-en-4-yn-1-ones crystallizing in chiral space groups have been investigated both theoretically and experimentally. It was shown that crystalline NLO susceptibility of the Br-derivative is comparable to such an NLO material as N-(4-nitrophenyl)-l-prolinol. The crystal packing effects on calculated NLO properties have been estimated based on the recently proposed Charge Model. Second-harmonic generation measurements of selected (E)-1,5-diarylpent-2-en-4-yn-1-ones confirmed a validity of the Charge Model and demonstrated an efficiency of this family for potential application as materials for nonlinear optics.