An unprecedented formation of new copper(II) complexes as bioactive materials based on copper-catalyzed click reaction

Abstract

1,2-cyclohexanedione-bis(p-fluorobenzohydrazone) (L) was synthesized as a bisaroylhydrazone type compound. This molecule was reacted with Cu(NO3)2·3H2O in CH3CN under ambient conditions, and consequently, different types of complexes were obtained: mononuclear copper(II) complexes with the general formula: [Cu(TE)(NO3)2] (1 and 2), and a trinuclear copper(II) complex: [{Cu3(μ3-OH)(T)3(NO3)2}2] (3) (TE: triazole-ester type ligands; T: triazole type ligands). These ligands are formed in situ as intermediates via the oxidation of L by Cu(II) ion on the basis of copper(II)-catalyzed reaction. The prepared compounds were characterized and their structures were determined based on various techniques. On the basis of X-ray crystallography, compounds 1 and 2 are confirmed as mononuclear copper(II) complexes. In each of these complexes, Cu is bound to the 1-N of two triazole-ester type ligands (monodentate ligand), and two binding nitrate ions. The main difference between 1 and 2 is that, in 1, the binding nitrate ions are bound to Cu(II) in a bidentate mode, and thus, the copper(II) ion is 6-fold coordinated in a distorted octahedral coordination environment. In 2, the binding nitrate ions are bound to Cu(II) in a monodentate mode, and hence, the copper(II) ion in this compound is 4-fold coordinated with a distorted square planar coordination environment. On the other hand, the asymmetric unit of 3 contains two independent molecules with identical constitution. The structure of each molecule comprises a {Cu3(μ3-OH)} core held up by three triazole type ligands and two binding nitrate ion. Moreover, the growth inhibitory activity of L, 1, 2 and 3 against some selected bacterial strains was evaluated. Based on this study, the prepared compounds have shown a differentiated growth inhibitory activity with respect to their lipophilic nature and structural features.