Synthesis and crystal structure of a tetranuclear five-coordinated copper(II) complex with Schiff-base of N-(3-carboxylsalicylidene)-4-(2-iminoethyl)-morpholine

A tetranuclear copper(II) complex Cu₄L₂(CH₃COO)₂(OH)₂]·6H₂O, in which L stands for the dianion of N-(3-carboxylsalicylidene)-4-(2-iminoethyl)morpholine, was synthesized and characterized by elemental analysis, IR, UV-Vis, TGA and X-ray single crystal diffraction. The crystal structure shows that the coordination unit is centrosymmetric with all the Cu(II) ions in square pyramidal coordination geometry. The coordination unit consists of two equivalent parts Cu₂L(CH₃COO)(OH)], each containing two Cu(II) ions, a tetradentate N₂O₂ Schiff base dianion L²⁻, a CH₃COO⁻, and a OH⁻ anion. In Cu₂L(CH₃COO)(OH)], the six coordination atoms (N₂O₄) are nearly coplanar, with Cu(1) and Cu(2) enchased in between; the phenolate oxygen and the OH⁻ oxygen as bridging atoms bind the two Cu(II) ions in close proximity; both O₄ around Cu(1) and N₂O₂ around Cu(2) form the basal plane of the coordination square pyramids. The two parts are connected by sharing two μ₃-OH⁻ oxygens and two μ₂-CH₃COO⁻ oxygens from each other, forming four edge-sharing coordination square pyramids around the four Cu(II) ions. A 3D network is formed through hydrogen bonding along a and c axis, and π-π interaction along b axis.