Synthesis, crystal structure and properties of the first trinuclear copper(ii) cryptate bridged by an imidazole anion

Abstract

The trinuclear copper(II) cryptate [Cu₃L(im)(Br)₂](ClO₄)₃·H₂O was studied, where im denotes the imidazolate anion and L is a reduced form cryptand which was synthesized by [2 + 3] Schiff-base condensation of tris(2-aminopropyl)amine with 2,6-diformylpyridine followed by reduction with NaBH₄. An ES-MS spectrum confirms the presence of a Cu₃L core and its dimer in the cryptate. X-Ray analysis shows that the three copper(II) centers are arranged in an isosceles triangles. Cu(1) is located in a N₄Br coordination environment with a square pyramidal configuration. Cu(2) and Cu(3) showed square planar configurations with N₃Br and N₄ coordination environments, respectively. Two nitrogens of an imidazole anion acting as a bridging ligand link Cu(1) and Cu(3). A weak interaction was found between Cu(2) and Br(1). Both intermolecular hydrogen bonds and the weak interaction between two molecules of cryptates via ClO₄⁻ resulted in the formation of a dimer of the cryptate. The magnetic interaction in the dimer was also studied.