Institution: | 1. State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002 P. R. China
University of the Chinese Academy of Sciences, Beijing, 100049 P. R. China;2. School of Chemistry & Chemical Engineering and School of Materials Science & Engineering, Hefei University of Technology, Hefei, Anhui, 230009 P. R. China;3. State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002 P. R. China |
Abstract: | Birefringent materials play a key role in modulating the polarization of light and thus in optical communication as well as in laser techniques and science. Designing new, excellent birefringent materials remains a challenge. In this work, we designed and synthesized the first antimony(III) fluoride oxalate birefringent material, KSb2C2O4F5, by a combination of delocalized π-conjugated C2O4]2− groups, stereochemical active Sb3+ cations, and the most electronegative element, fluorine. The C2O4]2− groups are not in an optimal arrangement in the crystal structure of KSb2C2O4F5; nonetheless, KSb2C2O4F5 exhibits a large birefringence (Δn=0.170 at 546 nm) that is even better than that of the well-known commercial birefringent material α-BaB2O4, even though the latter features an optimal arrangement of π-conjugated B3O6]3− groups. Based on first-principles calculations, this prominent birefringence should be attributed to the alliance of planar π-conjugated C2O4]2− anions, highly distorted SbO2F2 and SbOF3 polyhedra with a stereochemically active lone pair. The combination of lone-pair electrons and π-conjugated systems boosts the birefringence to a large extent and will help the development of high-performance birefringent materials. |