Synthesis, Structure and Properties of an Erbium(III) Complex with Chiral Salen-type Schiff Base Ligand

A new type of ionic ferroelectric based on a chiral salen-type Schiff base erbium(III) complex (ErL) was synthesized by the reaction of erbium nitrate with the ligand N,N′-bis(3,5-dichlorosalicylidene)-(1S,2S)-1,2-cyclohexylenediamine (L). The structures of the ligand L and the complex ErL were determined by single-crystal X-ray diffraction. The results indicated that ErIII not only acts as central metal atom to coordinate with two Schiff base ligands, but also as Lewis acid catalyst to promote the partial decomposition of another salen-type Schiff base ligand. The central ErIII atom adopts an octacoordinate square antiprismatic arrangement with Λ absolute configuration, coordinating with all nitrogen and oxygen atoms of two ligands due to the influence of the strong electron-withdrawing group on the Schiff base ligand. The complex ErL exhibits good SHG and ferroelectric properties. The results provide a simple and effective approach to construct rare earth complexes coordinated with nitrogen and oxygen atoms of salen-type Schiff base ligands with technologically important properties such as SHG activity and ferroelectricity.