Noncentrosymmetric Crystal [C<sub>10</sub>H<sub>8</sub>NO<sub>2</sub>]<sub>2</sub>SiF<sub>6</sub>·H<sub>2</sub>O with Large Birefringence
Liqin Liu, Hai‐Lan Huang, Mingliang Ding, Yaoguo Shen
Abstract
Crystals with noncentrosymmetric structures are applied in many fields, but reported compounds have a high probability of forming a centrosymmetric structure. Here, by hydrogen-bonding the π-conjugated [C 10 H 8 NO 2 ] + cation with the separated [SiF 6 ] 2– octahedron, a noncentrosymmetric isoquinoline hexafluorosilicate monohydrate optical crystal of [C 10 H 8 NO 2 ] 2 SiF 6 ·H 2 O was formed under the regulatory influence of hydrogen bonding. It not only possesses a moderate second harmonic generation response (1.0 × KDP) but also has a large birefringence (0.282 at 550 nm), which is greater than those of most commercial birefringent crystals. In addition, the UV–vis–NIR diffuse reflectance spectrum and thermal stability analysis are also reported. Our finding gives insight into how to design noncentrosymmetric structural compounds in the organic–inorganic system.