(C3N6H7)2SiF6·H2O: an ultraviolet birefringent crystal exceeding the intrinsic energy gap of an organic reagent

A new organic–inorganic hybrid compound (C 3 N 6 H 7 ) 2 SiF 6 ·H 2 O, in which [C 3 N 6 H 7 ] + groups are uniformly arranged under the regulation of SiF 6 octahedra, shows highly polarization anisotropy and a breakthrough in the energy gap.