Layered (C5H6ON)2[Sb2O(C2O4)3] with a large birefringence derived from the uniform arrangement of π-conjugated units

Abstract

An organic-inorganic hybrid antimony(III) oxalate (C5H6ON)2[Sb2O(C2O4)3] was successfully obtained by simultaneous combination of π-conjugated 4-hydroxypyridine and (C2O4)2- group with stereochemical active Sb(III) cation. The compound features a layered structure, and the equatorial planes of SbO6 units, the π-conjugated (C2O4)2- and (C5H6ON)+ groups are closer to planar arrangement, represent strong structural anisotropy that favors a large birefringence. As expected, (C5H6ON)2[Sb2O(C2O4)3] exhibits a large birefringence of 0.279 at 546 nm. Structural and theoretical analyses indicate that the combination of multiple π-conjugated units is a feasible approach for designing and exploring new superior birefringent materials.