Meng Xianghe, Liang Fei, Kang Kaijin, Tang Jian, Huang Qian, Yin Wenlong, Lin Zheshuai, Xia Mingjun
Beijing Center for Crystal Research and Development, Key Laboratory of Functional Crystals and Laser Technology, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
Dalton Trans. 2019 Jun 25;48(25):9048-9052. doi: 10.1039/c9dt01871a.
Ultraviolet (UV) transparent birefringent crystals are indeed indispensable for modern optoelectronics and polarizer devices. Herein, mixed alkali/alkali-earth metal hydroisocyanurates A2B(H2C3N3O3)4·nH2O (A = K, Rb, Cs; B = Mg, Ca; n = 4, 10) were synthesized and their thermal, vibrational and optical properties were characterized in detail. Although they crystallize in different crystallographic point groups, all compounds feature quasi-two-dimensional layered structures built by the 2∞[H2C3N3O3]- ribbons through hydrogen bonds, separated by water molecules and cations. Benefiting from the delocalized π-conjugated bonds and planar structural configuration of (H2C3N3O3)- groups, they show a concurrently short ultraviolet absorption edge (λcut-off ≈ 230 nm) and strong optical anisotropy (Δn ≈ 0.37 at 800 nm), twice larger than that of the benchmark UV birefringent crystal calcite.
紫外线（UV）透明双折射晶体对于现代光电子学和偏振器设备而言确实不可或缺。在此，合成了混合碱/碱土金属异氰尿酸氢盐A2B(H2C3N3O3)4·nH2O（A = K、Rb、Cs；B = Mg、Ca；n = 4、10），并详细表征了它们的热、振动和光学性质。尽管它们结晶于不同的晶体学点群，但所有化合物都具有由2∞[H2C3N3O3]-带通过氢键构建的准二维层状结构，由水分子和阳离子分隔。受益于（H2C3N3O3）-基团的离域π共轭键和平面结构构型，它们同时具有短的紫外线吸收边缘（λ截止≈230 nm）和强的光学各向异性（在800 nm处Δn≈0.37），是基准UV双折射晶体方解石的两倍。
