Halogen Substitution Driven Crystal Engineering of Chalcones: Mechanisms and Optimization for Spatial Ordering and Nonlinear Optical Performance

Abstract

Chalcones, α,β-unsaturated ketones with typical donor-π-acceptor (D-π-A) structures, are widely used in optoelectronic devices due to their excellent nonlinear optical (NLO) properties, such as second-harmonic generation and electro-optic modulation. However, further enhancing their NLO performance is constrained by the optimization of molecular spatial arrangement and precise control of electronic structure. Recently, halogen substituents (F, Cl, Br, I) have emerged as crucial tools for modulating the properties of chalcone derivatives, owing to their unique electronic effects (electron-withdrawing ability, polarizability) and steric effects (volume, hindrance). This review systematically examines how halogen substituents modulate intramolecular charge transfer (ICT), extend the π-conjugation system, and control molecular packing modes in chalcone derivatives. By integrating theoretical calculations with experimental case studies, we propose multi-dimensional optimization strategies and explore their potential in next-generation NLO materials.