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Zn(H2C3N3O3)2·3H2O: the first single-d10 transition metal based ultraviolet hydroisocyanurate crystal with large birefringence.

Birefringent crystals can modulate and detect the polarization of light, and have been widely used in the field of optoelectronic devices. The combination of a d10 transition metal cation and π-conjugated (H2C3N3O3)- group is a feasible approach for the synthesis of new crystal structures possessing large birefringence and short cutoff edges. Herein, a new hydroisocyanurate birefringent material Zn(H2C3N3O3)2·3H2O (ZHCY) was synthesized by a mild hydrothermal method. ZHCY featured a 2D layered ribbon structure constituted by coplanar π-conjugated (H2C3N3O3)- hydroisocyanurates, and displayed a wide band gap (5.24 eV) and a large birefringence (Δnexp ∼ 0.323, Δncal = 0.283 at 800 nm). Theoretical calculations revealed that its optical properties mainly originated from the π-conjugate coplanar (H2C3N3O3)- groups, which contribute to the enhancement of birefringence.