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

Abstract

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 (Δn_exp ∼ 0.323, Δn_cal = 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.