Unusual two-step sequential reversible phase transitions with coexisting switchable nonlinear optical and dielectric behaviors in [(CH3)3NCH2Cl]2[ZnCl4</ sub>]

作者：Liao, Wei-Qiang^*; Gao, Ji-Xing; Hua, Xiu-Ni; Chen, Xiao-Gang; Lu, Yang

来源：Journal of Materials Chemistry C, 2017, 5(45): 11873-11878.

DOI：10.1039/c7tc04095d

• SYMMETRY-BREAKING
• MOLECULES
• CONSTANT
• CRYSTALS
• DESIGN

A novel material with coexisting switchable nonlinear optical (NLO) and dielectric properties, [trimethylchloromethyl ammonium](2)[ZnCl4] [(TMCM)(2)-ZnCl4], which undergoes two reversible solid state phase transitions at 337 K (Tc-1) and 258 K (T-c2), respectively, has been successfully synthesized and grown as Nock crystals. Exceptionally, variable-temperature X-ray single crystal structural analyses of (TMCM)(2)-Zncl(4) reveal that the unusual space group changes from P2(1)2(1)2(1) at 223 K to P2(1)/c between 7(c2) and T-c1 to Pmcn above T-c1. As expected, the dielectric value of (TMCM)(2)-ZnO4 exhibits two remarkable step-Like enlargements around T(c1)and T-c2, indicating that it exhibits a Low dieLectric state, an intermediate dieLectric state and a high dieLectric state. In particular, the second harmonic generation (SHG) efficiency shows a sharp step-Like increase from almost zero to 0.47, and its SHG activities in a high-NLO state can be recovered after several cycles without any attenuation. The transitions of (TMCM)(2)-ZnO4 could be intrinsically ascribed to the sequential order disorder transformations of both the cations and anions. ALL these results demonstrate its potential application as a switchable and tunable molecular dieLectric and NLO material.

• 出版日期2017-12-7
• 单位东南大学