Two Novel Noncentrosymmetric Zinc Coordination Compounds with Second Harmonic Generation Response, and Potential Piezoelectric and Ferroelectric Properties

Hydrothermal treatments of ZnCl2 and organic ligands afforded two novel noncentrosymmetric coordination compounds 1 and 2, respectively. 1 crystallizes in the chiral P212121 space group because of the introduction of a bent ligand 3-(2-(2-pyridyl)ethenyl)benzoic acid to the complex, whereas 2 crystallizes in hexagonal crystal system (R3) with a 3-fold axis and bears two octahedral chelate zinc cation and two [ZnBr4]2−. Both 1 and 2 display a strong second harmonic generation (SHG) response and moderate piezoelectric properties. Because of the assignment of a polar point group of chiral space group for compound 2 (R3), its electric hysteresis loop was recorded; we found that it may be a potential ferroelectric with spontaneous polarization of 0.02 μC/cm2.