Synthesis and structural features of copper(II) complexes of N,N,N′,N′-tetramethylethylenediamine with 2-chlorobenzoate¹⁻ and 2-hydroxybenzoate¹⁻

Two copper(II) coordination complexes, formulated as [Cu(tmen)(Clba)₂] (1) and [Cu(tmen)(Hsal)₂·H₂O] (2) (where tmen = N,N,N′,N′-tetramethyl ethylenediamine (C₆H₁₆N₂), Clba¹⁻ = 2-chlorobenzoate (C₇H₄ClO₂ ¹⁻), and Hsal¹⁻ (C₇H₅O₃ ¹⁻ = monoanion of o-hydroxybenzoic acid (salicylic acid)), have been synthesized and characterized by elemental combustion analysis, spectroscopic techniques, thermal studies, and single crystal X-ray analyses. Complex 1 consists of two distinct monomeric units in which the coordination environment around the central copper(II) ion is a distorted octahedron with a CuN₂O₄ chromophore, constituted by a chelating tmen molecule, and two 2-chlorobenzoate¹⁻ anions coordinated through their carboxylate-O atoms in an asymmetrical bidentate fashion. Complex 2 is also a monomer and consists of an CuN₂O₃ chromophore, in which tmen is coordinated to Cu(II) through its two N atoms in a chelating bidentate fashion, and an aqua-O and the two o-hydroxybenzoate¹⁻ (HSal¹⁻) anions are coordinated through one of their carboxylate-O atoms in a monodentate mode, forming a square pyramidal structure. Hydrogen bonding interactions especially of O–H…O, N–H…O, and C–H…Cl types interweave monomeric units and stabilize the overall crystal structures in both complexes. Thermal analysis and antibacterial activities of 1 and 2 against various bacterial strains were also investigated.