Two UV optical crystals with strong optical anisotropy, large band gaps and an α-BBO type structure

The [B3O6] group has attracted a lot of attention as α-BaB2O4 (α-BBO) is composed of the [B3O6] group showing a short UV cut-off edge and a large birefringence. However, it is difficult to synthesize novel crystals with properties beyond α-BBO using [B3O6] as a fundamental building block (FBB). Hence, we successfully synthesized two cases of α-BBO-type organic–inorganic hybrid compounds using α-BBO as the template and melamine [C3N6H6] as the fundamental building block. The coplanar and parallel arrangement of π-conjugated [C3N6H6] groups makes them exhibit excellent optical properties, including improved birefringence responses (0.264 and 0.243@546 nm) and wide bandgaps (4.12 and 4.20 eV).