Structural and magnetic characterization of 1-D complexes constructed from pyrazole-3,5-dicarboxylate bridging multi copper(II) centers

Abstract

In aqueous solution, the reaction of Cu(ClO4)2 and di(2-pyridylmethyl)amine, DPA with the disodium salt of pyrazole-3,5-dicarboxylate (Na2Hpzdc) in presence of sodium azide afforded the azido complex [Cu3(DPA)3(μ-pzdc)(μ-N3)](ClO4)2·2H2O (1) whereas when reaction was conducted in absence of sodium azide the perchlorato complex [Cu3(DPA)3(μ-pzdc)(μ-ClO4)](ClO4)2·3H2O (2) was obtained. The complexes were structurally characterized by physicochemical techniques and by single crystal X-ray crystallography in case of 1. The coordination sphere of the two complexes which are iso-structural polymeric 1D systems consist of three independent Cu(DPA) units, one pzdc bridging ligand and one end-on bridging azido group in 1 or one bridging perchlorato group in 2. The three Cu(II) centers in both complexes may be described as axially elongated octahedral. Magnetic susceptibility measurements reveal the weak anti-ferromagnetic coupling in the two complexes (J=−23.2cm−1 for 1 and −14.8cm−1 for 2).