Two van der Waals Layered Antimony(III) Phosphites as UV Optical Materials

Herein, two new Sb³⁺-based phosphites, Sb₂O₂(HPO₃) (I) and Sb₂O(HPO₃)₂ (II), were successfully obtained by ingeniously combining Sb³⁺-based polyhedra containing stereochemically active lone pair (SCALP) and HPO₃ polar groups. Both reported compounds exhibit unique 2D van der Waals layered structures, [Sb₄O₄(HPO₃)₂]_∞ and [Sb₂O(HPO₃)₂]_∞, respectively, which favors compounds with large optical anisotropy. Interestingly, the different curvatures of the two layers resulted in the two title compounds showing significantly different birefringences (0.079@546 and 0.046@546 nm, respectively). Both compounds endow wide optical band gaps (4.32 and 4.54 eV, respectively), which indicates their potential as promising ultraviolet (UV) birefringent crystals. The synthesis of the two title compounds enriched Sb³⁺-based phosphites in the UV region and provided guidance for the subsequent synthesis of superior optical materials.