Sr₂Zn(C₃N₃O₃)₂: An AlkalineEarth and <i>d</i>¹⁰ Transition Metal Based UltravioletCyanurate with Large Birefringence

Birefringent properties of materials have garnered significant interest in both the military and civilian scientific domains. The rational combination of mixed alkaline earth and fully filled <i>d</i>¹⁰ transition metal cations in the cyanurates may achieve large birefringence and good transparency in the UV region by regulating planar π-conjugated (C₃N₃O₃)^3– anions. This work successfully synthesized a new metal cyanurate Sr₂Zn(C₃N₃O₃)₂ (SZCY) by a solid-state cyclo-trimerization reaction featuring a planar π-conjugated laminar crystal structure. SZCY displays a wide bandgap (<i>E</i>_g ∼ 5.30 eV) and large birefringence (Δ<i>n</i> = 0.31 at 1064 nm). The first-principles calculation revealed that the optical properties of SZCY are mainly due to the parallel arrangement of (C₃N₃O₃)^3– groups.