Molecular Structure Design, Crystal Growth, and Characterization of New Types of Organic Nonlinear Optical Chalcone Crystals

Chalcone structures obtained by structural tailoring are an important class of molecular organic nonlinear optics (NLO) crystals that can be used for multiple purposes. In this work, two novel chalcone compound crystals with non-centrosymmetric structures, 6MN3MPP (C21H18O3, Pca21) and 6MN4MPP (C21H18O3, Pn), were designed and grown by extending the π-conjugation and structure-modifying strategy. On this basis, the second harmonic generation (SHG) efficiency, thermal stability, transmission spectra, dielectric constant, and photoluminescence properties of the crystal were characterized, and the hyperpolarizability of the crystal was theoretically calculated. The results show that the synthesized crystals exhibit higher crystal transparency (≥70%), higher melting point, and lower dielectric constant (εr≈ 6.5) compared with other reported chalcone NLO crystals. In particular, the SHG intensity of the 6MN3MPP crystal is 4.3 times higher than that of the KDP crystal. All of the results show that the two newly synthesized compounds have good application prospects as NLO crystals.