Structural Design and Characterization of NLO Crystals Containing Alkoxy Chalcone Derivatives with High SHG Efficiency

By changing the position of the methoxy functional group in the chalcone molecule, a type of chalcone organic nonlinear crystals of DMPE (C18H18O3) and 3-DMPE (C18H18O3) was successfully synthesized, and high-quality crystals were grown by the solution method. The structural, optical, thermal, and dielectric properties of these crystals were comprehensively analyzed. First-principles calculations and experimental measurements revealed that DMPE exhibits superior second harmonic generation (SHG) efficiency compared to 3-DMPE, which is attributed to its molecular packing arrangement and charge transfer. HOMO–LUMO gap analysis indicated a smaller gap for DMPE (3.84 eV) compared with 3-DMPE (3.91 eV), making DMPE more responsive to external excitations. The band structures and density of states calculations confirmed the contributions of π-conjugated systems and electron-donating groups to the nonlinear polarization. Additionally, DMPE demonstrated a higher thermal stability (melting point of 109.8 °C) and better dielectric properties, highlighting its potential for advanced optoelectronic applications.