An organic–inorganic hybrid birefringent material with diverse functional groups

Abstract

Birefringent materials are vital materials to modulate the polarization of light, and play a key role in plorization devices such as linear optical devices, optical communication devices, and fiber optic sensors. It is still a challenge to design excellent birefringent materials. Herein, we report an organic–inorganic hybrid oxalate birefringent material, (CN₄H₇)SbC₂O₄F₂(H₂O)_0.5, by introducing organic delocalized π-conjugated [CN₄H₇]⁺ and [C₂O₄]²⁻ groups, and stereochemical active inorganic SbO₄F₂ polyhedra. (CN₄H₇)SbC₂O₄F₂(H₂O)_0.5 exhibits a large birefringence (Δn = 0.126@546 nm) that is almost equal to that of the well-known birefringent material α-BaB₂O₄. Theoretical calculations reveal that the distinguished birefringence should stem from the synergistic arrangement of π-conjugated [CN₄H₇]⁺ and [C₂O₄]²⁻ planar groups, and highly distorted SbO₄F₂ polyhedra with a stereochemically active lone pair. The synergistic effect of π-conjugated systems and the lone pair electrons greatly boosts the birefringence, which is helpful for the development of high-performance birefringent materials.