Noncentrosymmetric (C<sub>3</sub>H<sub>7</sub>N<sub>6</sub>)<sub>6</sub>(H<sub>2</sub>PO<sub>4</sub>)<sub>4</sub>(HPO<sub>4</sub>)·4H<sub>2</sub>O and Centrosymmetric (C<sub>3</sub>H<sub>7</sub>N<sub>6</sub>)<sub>2</sub>SO<sub>4</sub>·2H<sub>2</sub>O: Exploration of Acentric Structure by Combining Planar and Tetrahedral Motifs via Hydrogen Bonds
Shu‐Fang Li, Liang Hu, Yao Ma, Fei‐Fei Mao, Jie Zheng, Xiu‐Du Zhang, Dong Yan
Abstract
The combination of organic and inorganic nonlinear active units to obtain organic–inorganic hybrid materials has been proved to be a very effective method to obtain nonlinear optical (NLO) materials with excellent properties. Herein we reported two hybrid melamine-based compounds, namely, acentric (C3H7N6)6(H2PO4)4(HPO4)·4H2O (1) and centrosymmetric (C3H7N6)2SO4·2H2O (2), which were synthesized via facile solvent evaporation method. Compound 1 features a three-dimensional (3D) network structure composed of ∞[(H2PO4)4(HPO4)(H2O)4]6– layers which are further linked with ∞[(C3H7N6)6]6+ layers via hydrogen bonds. Compound 2 displays a 3D structure composed of [(C3H7N6)2(SO4)(H2O)2]∞ layers further linked with each other by hydrogen bonds. Compound 1 presents a second harmonic generation signal of about 0.1 × KDP. Furthermore, UV–vis and infrared spectra, thermal analyses, and theoretical calculation were also adopted to evaluate its NLO performance. The theoretical calculations showed that the SHG response and large birefringence of 1 were primarily caused by the (C3H7N6)+, (H2PO4)−, and (HPO4)2– groups.