[C3N6H7]2[B3O3F4(OH)]: a new hybrid birefringent crystal with strong optical anisotropy induced by mixed functional units

Abstract

The design and preparation of new birefringent materials with large birefringence, especially those for the short-wavelength spectral region, are still active since they play an important role in creating polarized light. Herein, a new organic–inorganic hybrid fluorooxoborate [C₃N₆H₇]₂[B₃O₃F₄(OH)] was discovered following the strategy of combining two birefringence-active units to increase the optical anisotropy. The large birefringence (0.440@546 nm) and short absorption edge (240 nm) make [C₃N₆H₇]₂[B₃O₃F₄(OH)] a potential short-wavelength ultraviolet birefringent crystal. Both the [C₃N₆H₇] cation and [B₃O₃F₄(OH)] anion in [C₃N₆H₇]₂[B₃O₃F₄(OH)] are identified as birefringence-active units that induce large optical anisotropy, as evidenced by additional theoretical calculations.