Synthesis and structural characterization of copper(II) complexes with a tetradentate semicarbazone ligand derived from 2,5-hexadione

Four Cu(II) complexes [CuLH₂O](ClO₄)₂, 1; [CuLCl]Cl.H₂O, 2; [CuLBr]₂(Cu₃Br₅), 3; and [CuLH₂O](NO₃)₂, 4; where L = tetradentate semicarbazone ligand, have been synthesized and characterized by elemental analysis, FT-IR and UV–Vis. The structures of compounds 1 and 3 have been determined by single-crystal X-ray diffraction analyses. In mononuclear 1, the semicarbazone, L acts as a tetradentate neutral ligand and a water molecule also coordinates to the Cu atom. There are two independent [CuL(H₂O)]²⁺ cations and four perchlorate anions in the crystallographic asymmetric unit. One of the cations has a weak interaction between its Cu atom and a O atom of an adjacent perchlorate anion. The structure of 3 contains two independent [CuLBr]⁺ cations and a (Cu₃Br₅)²⁻ anion. The coordination geometry around the cation’s Cu(II) ion is five-coordinated square pyramidal, with L acting as a tetradentate neutral ligand and with a Br at the apical position. The Cu₃Br₅ ²⁻ anions link to one another to form an infinite one-dimensional (Cu₃Br₅ ²⁻)_n chain. Furthermore, the Hirshfeld surface analyses and the 2D fingerprint plot have been discussed.