New silver(I) complex with diazafluorene based ligand: Synthesis, characterization, investigation of in vitro DNA binding and antimicrobial studies

Abstract

A novel diazafluorene based complex with silver, [Ag(dian)2]NO3, where dian is N-(4,5-diazafluoren-9-ylidene)aniline, has been prepared and characterized by elemental analysis, IR spectroscopy, 1HNMR, UV–Vis spectroscopy and cyclic voltammetry. In order to explore the relationship between the structure and biological properties, DNA binding propensity and in vitro antibacterial property have also been studied. The mode of DNA-complex interaction has been investigated by electronic absorption titration, luminescence titration, competitive binding experiment, effect of ionic strength, thermodynamic studies, viscometric evaluation, circular dichroism spectroscopy and cyclic voltammetry. The results reveal that the complex binds to CT-DNA in a moderate intercalation capability with the partial insertion of a planar dian ligand between the base stacks of double-stranded DNA with binding constant (Kb) of 2.4 × 105 M−1. The viscosities and CD spectra of the DNA provide strong evidence for the intercalation. An in vitro antibacterial efficacy of the Ag(I) complex on a series of Gram-positive bacteria (Staphylococcus aureus, Enterococcus faecalis) and Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa) indicates that the complex exhibits a marked antibacterial activity. The minimum inhibitory concentrations of the complex indicate that it exhibits much higher antibacterial effect on standard bacterial strains of Escherichia coli and Staphylococcus aureus than those of silver nitrate, silver sulfadiazine. The bacterial inhibitions of the silver(I) complex are closely agreed to its DNA binding affinities.