Two new Cu(II) /m-hydroxybenzoato complexes with chloro- and carboxylato-bridged dinuclear [Cu(μ_2-Cl)(μ_2-COO)Cu] cores

摘要

In aqueous methanolic solution, reactions of CuCl_2, m-hydroxybenzoic acid (HL), and NaOH with 2,2'-bipyridine (bpy) and 1,10-phenanthroline (phen) at room temperature afforded {[Cu(bpy)L] (μ_2-Cl)(μ_2-L)[Cu(bpy)L]}-1.2H_2O (1) and {[Cu(phen)Cl](μ_2-Cl)(μ_2-L)[Cu(phen)L]} (2) with chloro- and carboxylato-bridged dinuclear [Cu(μ_2-Cl)(μ_2-COO)Cu] cores. The Cu_2 dimers in 1 are pairwise aggregated to form H-bonded tetranuclear motifs, which are extended by H_2O into 1-D H-bonded chains and further assembled into 2-D supramolecular networks. The Cu_2 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 Cu~(2+) ions are dominant in these dinuclear [Cu(μ_2-Cl)(μ_2-COO)Cu] cores. To the best of our knowledge, 2, crystallizing in the acentric polar orthorhombic space group Pna2_1, represents the first example of metal w-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).