Synthesis, characterization, DFT calculations, and biological activity of copper(II) complexes with 1,1,1-trifluoro-4-(2-methoxyphenyl)butan-2,4-dione

In the present work, complex formation equilibria between copper(II) and 1,1,1-trifluoro-4-(2-methoxyphenyl)butan-2,4-dione (1) have been investigated by UV–vis spectroscopy in ethanol/0.01 M NEt4NO3 as an ionic strength adjuster at 25 °C. The composition of the complex in solution was determined using Job's plot and molar ratio method. Four single crystals of copper complexes CuL2(DMF) (2), CuL2 (3), CuL2(DMSO)2 (4) and CuL2(DMSO) (5), which include the ligand molecules in the cis- and trans-conformations, respectively, were obtained. The complexes were characterized with FT-IR spectroscopy, elemental analysis, and X-ray crystallography. In the complexes 2 and 5, the copper atoms adopt distorted square pyramidal coordination polyhedra formed by oxygen atoms, whereas the geometry around the copper atom in the complexes 3 and 4 can be described as square planar and square bipyramidal, respectively. Cu–O bond lengths were calculated within the density functional theory using two different functionals, viz., BP86 and B3LYP, in combinations with Ahlrichs and Pople basis sets to be compared with each other and with experimentally determined values. Compounds 1–4 were tested for their in vitro antimicrobial activity and found active to a variable extent. According to measured minimum inhibitory concentrations (MIC), the title complexes show comparable or higher activity against bacteria and yeast with respect to the free ligand. It was shown that the biological activity is induced by intact complexes and is not resulted from the complex decomposition into copper(II) ions and the free ligand. © 2018