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Updated: Sep 19, 2025
From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
Published on: March 24, 2018
Halide Ion-Directed Symmetry Control in π-Conjugated Molecular Crystals
Yu Zhang1, Han Luo1, Shunke Zhang1
1College of Chemistry and Materials Science, Sichuan Normal University, Chengdu 610066, P. R. China.
None:
Two halide-containing π-conjugated molecular crystals, (C5H7BNO2)Cl and (C5H7BNO2)Br, were synthesized using pyridine-4-boronic acid and halide ions of differing ionic radii. (C5H7BNO2)Cl adopts a noncentrosymmetric (NCS) structure and exhibits SHG efficiency comparable to KH2PO4, along with a wide UV transparency window, making it promising for UV NLO applications. In contrast, (C5H7BNO2)Br crystallizes in a centrosymmetric (CS) structure, exhibiting enhanced birefringence. Structural and theoretical analyses reveal that the halide ions influence molecular packing and coplanarity, thereby tuning the symmetry and optical properties. This work demonstrates a halogen-engineering strategy for symmetry control and optical property modulation in π-conjugated molecular crystals, offering a viable pathway for the rational design of high-performance UV NLO materials.
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