A novel iron(III) complex: synthesis, spectra, X-ray structure photoluminescence study, and antibacterial properties

Abstract

The binuclear iron(III) complex of the formula {[Fe(5,5′-dmbpy)2(OH2)]2(µ-O)}(NO3)4 was prepared from the reaction of Fe(NO3)3·9H2O with 5,5′-dimethyl-2,2′-bipyridine. The complex was characterized by FT-IR, UV–Vis, TGA, 1HNMR spectroscopy, elemental analysis, and luminescence measurements. Its structure was investigated using the single-crystal diffraction method. Crystal structure analysis showed that two crystallographically distinct oxygen-bridged Fe(III) cations are each coordinated by two bidentate ligands and one water molecule, resulting in a distorted coordination octahedron formed by four nitrogen atoms and two oxygen atoms. Several types of hydrogen bonds stabilize the crystal packing. In vitro biological screening of the free ligand, the complex and its metal salt against diverse microorganisms was done using the micro-dilution (tube) broth method. The antibacterial effects were also examined in vitro against standard bacterial strains, the Gram-positive Staphylococcus aureus, S. aureus ATCC 25923, and the Gram-negative Escherichia coli; E. coli ATCC 25922. Using these strains, the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and inhibition zones (IZ) were obtained for the complex, its ligand (5,5′-dmbipy) and its metal salt with Fe(NO3)3.9H2O.