Two new Cu(II) m-hydroxybenzoato complexes with chloro- and carboxylato-bridged dinuclear [Cu(µ₂−Cl)(µ₂−COO)Cu] cores

Abstract

In aqueous methanolic solution, reactions of CuCl₂, m-hydroxybenzoic acid (HL), and NaOH with 2,2'-bipyridine (bpy) and 1,10-phenanthroline (phen) at room temperature afforded {[Cu(bpy)L](µ₂−Cl)(µ₂−L)[Cu(bpy)L]}⋅1.2H₂O (1) and {[Cu(phen)Cl](µ₂−Cl)(µ₂−L)[Cu(phen)L]} (2) with chloro- and carboxylato-bridged dinuclear [Cu(µ₂−Cl)(µ₂−COO)Cu] cores. The Cu₂ dimers in 1 are pairwise aggregated to form H-bonded tetranuclear motifs, which are extended by H₂O into 1-D H-bonded chains and further assembled into 2-D supramolecular networks. The Cu₂ dimers in 2 are also linked into 1-D H-bonded chains and further assembled into 2-D supramolecular layers. Magnetic measurements indicate that significant antiferromagnetic interactions (J = −15.9, −12.2 cm⁻¹) between Cu²⁺ ions are dominant in these dinuclear [Cu(µ₂−Cl)(µ₂−COO)Cu] cores. To the best of our knowledge, 2, crystallizing in the acentric polar orthorhombic space group Pna2₁, represents the first example of metal m-hydroxybenzoato complexes with ferroelectric properties with a remnant polarization (Pr) of ca. 0.04 µC cm⁻², coercive field (Ec) of ca. 2.52 kV cm⁻¹, and saturation of the spontaneous polarization (Ps) at ca. 0.195 µC cm⁻².

Keywords:

• Cu(II) Complexes
• Dinuclear [Cu(µ₂−Cl)(µ₂−COO)Cu] core
• m-Hydroxybenzoic acid complexes
• Magnetism
• ferroelectricity

Acknowledgments

This project was sponsored by K.C. Wong Magna Fund in Ningbo University and supported by the Scientific Research Fund of Zhejiang Provincial Education Department.