Sb 2 O 2 SeO 3 and Sb 2 O(SeO 3 ) 2 : Two-Layered Antimony(III) Selenites with Enhanced Birefringence.

Two antimony selenites, Sb 2 O 2 SeO 3 and Sb 2 O(SeO 3 ) 2 , were synthesized by simultaneously incorporating stereochemically active lone pair electrons containing SeO 3 2- and Sb 3+ . These compounds are structured with [SbO x ] polyhedra and [SeO 3 ] units within a two-dimensional framework. Both of them exhibit cutoffs at 300 and 330 nm within the ultraviolet (UV) range and demonstrate significant birefringence, with indices of 0.069 and 0.126 at 546 nm, respectively. These properties highlight their potential as UV birefringent materials. Structural analyses and theoretical calculations reveal that their exceptional birefringence results from the synergistic interactions between SeO 3 2- anions and Sb 3+ cations.