Synthesis, structural studies and biological activity of novel Cu(II) complexes with thiourea derivatives of 4-azatricyclo[5.2.1.02,6]dec-8-ene-3,5-dione.

The new Cu(II) complexes of 1/2/3-(bromophenyl)-3-(1,7,8,9-tetramethyl-3,5-dioxo-4-azatricyclo[5.2.1.02,6]dec-8-en-4-yl)thiourea derivatives have been synthesized. The spectroscopic studies together with density functional theory calculations of Cu(II) complexes revealed that two parent ligands coordinate to the copper cation in bidentate fashion via thiocarbonyl S and deprotonated N atoms forming rarely observed four-membered chelate ring, with nearly planar [CuN2S2] moiety. In solid state, the mononuclear complex is formed for thiourea derivative with 3-bromophenyl, whereas for Cu(II) connection with 2- and 4-bromophenyl-thioureas the formation of dinuclear complexes is observed, the latter formed by the stacking of mononuclear complexes. The microbiological activity of novel compounds has been evaluated. The Cu(II) complex with 4-bromophenyl ring connected to the thiourea moiety showed significant inhibition against standard strains of S. aureus and S. epidermidis. The range of minimal inhibitory concentration values is 2–4 μg/mL. That compound exhibited antibiofilm potency and effectively inhibited the formation of biofilm of methicillin-susceptive strain of S. epidermidis ATCC 12228. Moreover, the cytotoxicity against the MT-4 cells of all obtained complexes has been evaluated. The complexes turned out to be non-cytotoxic for exponentially growing MT-4