(C 8 H 7 N 2 O 2 ) 2 [Bi 2 Br 8 ]·2H 2 O and (C 8 H 7 N 2 O 2 ) 6 [Bi 2 Cl 10 ]Cl 2 ·2H 2 O: Exploring Birefringent Crystals in Hybrid Halide Systems.

In this study, new hybrid birefringent crystals of (C 8 H 7 N 2 O 2 ) 2 [Bi 2 Br 8 ]·2H 2 O and (C 8 H 7 N 2 O 2 ) 6 [Bi 2 Cl 10 ]Cl 2 ·2H 2 O were successfully synthesized by introducing a new birefringent group [C 8 H 7 N 2 O 2 ] + by a simple aqueous solution evaporation method. They crystallize in the P 2 1 / n space group, and their structure consists mainly of the π-conjugated group [C 8 H 7 N 2 O 2 ] + and the octahedron centered on Bi 3+ . By first-principles calculations, the birefringence response comes from the [C 8 H 7 N 2 O 2 ] + group with a planar π-conjugated structure. Meanwhile, the synthesis, structure, first-principles calculations, and optical properties are reported in this paper.