Syntheses, characterization and molecular structures of calcium(II) and copper(II) complexes bearing O 2-chelate ligands: DNA binding, DNA cleavage and anti-microbial study

Abstract

A new set of supramolecular complexes, [Cu(PMP) 2] [1], [Cu(MCPMP) 2] [2] and [Cu(PTPMP) 2] [3] (PMP = 5-methyl-4-(4-methyl-benzoyl)-2-phenyl-2,4-dihydro-pyrazol-3-one, MCPMP = 2-(3-chloro-phenyl)-5-methyl-4-(4-methyl-benzoyl))-2,4-dihydro-pyrazol-3-one and PTPMP = 5-methyl-4-(4-methyl-benzoyl)-2-p-tolyl-2,4-dihydro-pyrazol-3-one) have been synthesized and characterized by elemental analysis, metal estimation, molar conductivity, IR, UV–Vis and TG-DTA. The molecular geometry of one of these complexes has been determined by single crystal X-ray study. The X-ray diffraction analyses of the complexes show that the Cu(II) ion center is four-coordinated. The interaction of Cu(II) complexes with pET30a plasmid DNA was investigated by Viscosity and fluorescence spectroscopy. Results suggest that the copper complexes bind to DNA via an intercalative mode and can quench the fluorescence intensity of EB bound to DNA. The interaction between the complexes and DNA has also been investigated by agarose gel electrophoresis, interestingly, we found that the Cu(II) complexes can cleave circular plasmid DNA to nicked and super coiled forms. The complexes were screened for their anti microbial activity against Gram positive ( Bacillus subtilis) and Gram negative ( Escherichia coli). In the preparation of these complexes the acyl pyrazolone ligands are used and prepared by method suggested by Jensen. In contrast to conventional Claisen condensations, this method produces acyl derivative of the pyrazolone in good yield and is relatively easy to prepare. In these synthesis, condensations of acid chlorides with pyrazolones in dioxane, catalyzed by suspended calcium hydroxide results Ca(II) intermediate complex and then decomposition in 2 M hydrochloric acid to give acyl pyrazolone ligands. The intermediate Ca(II) complex, [Ca(PMP) 2(EtOH) 2], was isolated for the first time and its crystal structure is reported. The crystal structure of Ca(II) complex is stabilized by O–H⋯N, C–H⋯π and π–π stacking interactions.