Wei Qi, Cheng Jian-Wen, He Chao, Yang Guo-Yu
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences , Fuzhou, Fujian 350002, China.
Inorg Chem. 2014 Nov 3;53(21):11757-63. doi: 10.1021/ic502044d. Epub 2014 Oct 15.
A novel noncentrosymmetric calcium borate, Ca2[B5O9]·(OH)·H2O (1), was synthesized under solvothermal condition using mixed solvents of pyridine and H2O. Compound 1 crystallizes in the monoclinic space group Cc. Its structure contains [B5O12] units and features a three-dimensional (3D) pcu net with nine-membered ring (9-MR) channels along the b-axis, where the Ca(2+) cations, OH(-) ions, and H2O molecules are located. Each Ca polyhedron shares three edges and one vertex with four neighbors to form a 3D dia Ca-O network. The pcu B-O net and dia Ca-O net are further interpenetrated to give the final denser net. The second harmonic generation (SHG) measurement shows that compound 1 is a type I phase-matchable material with a strong SHG response of ∼3 times that of KH2PO4. In addition, it exhibits a wide transparency range with a short UV cutoff edge below 200 nm. These results reveal that the compound is a potential deep-UV nonlinear optical material. The Vienna ab initio theoretical studies indicate the good SHG response is derived from the synergistic effect of the π-conjugated systems of BO3 groups and distorted CaO9 polyhedra.
一种新型的非中心对称硼酸钙Ca2[B5O9]·(OH)·H2O (1)，采用吡啶和水的混合溶剂在溶剂热条件下合成。化合物1结晶于单斜空间群Cc。其结构包含[B5O12]单元，具有沿b轴的三维(3D) pcu网络，其中有九元环(9-MR)通道，Ca(2+)阳离子、OH(-)离子和H2O分子位于其中。每个Ca多面体与四个相邻体共享三条边和一个顶点，形成三维dia Ca-O网络。pcu B-O网络和dia Ca-O网络进一步相互贯穿，形成最终更致密的网络。二次谐波产生(SHG)测量表明，化合物1是一种I型相位匹配材料，其强SHG响应约为KH2PO4的3倍。此外，它具有宽透明范围，在200 nm以下有短的紫外截止边缘。这些结果表明该化合物是一种潜在的深紫外非线性光学材料。维也纳从头算理论研究表明，良好的SHG响应源于BO3基团的π共轭体系和畸变的CaO9多面体的协同效应。
