Synthesis, Characterization, DNA Cleavage, and Antimicrobial Studies of Some Transition Metal Complexes With a Novel Schiff Base Derived From 2-Aminopyrimidine

Antibacterial Activity of 2-Picolyl-polypyridyl-Based Ruthenium (II/III) Complexes on Non-Drug-Resistant and Drug-Resistant Bacteria

A new hexadentate 2-picolyl-polypyridyl-based ligand (4, 4'-(butane-1, 4-diylbis(oxy))bis(N, N-bis(pyridin-2-ylmethyl)aniline)) (2BUT) (1) and its corresponding Ru(II/III) complexes were synthesized and characterized, followed by assessment of their possible bioactive properties towards drug-resistant and non-drug-resistant bacteria. Spectroscopic characterization of the ligand was done using proton NMR, FTIR, and ESI-MS, which showed that the ligand was successfully synthesized. The Ru(II/III) complexes were characterized by FTIR, UV/Vis, elemental analysis, proton NMR, ESI-MS, and magnetic susceptibility studies. The analysis of ESI-MS data of the complexes showed that they were successfully synthesized. Empirical formulae derived from elemental analysis of the complexes also indicated successful synthesis and relative purity of the complexes. The important functional groups of the ligands could be observed after complexation using FTIR. Magnetic susceptibility data and electronic spectra indicated that both complexes adopt a low spin configuration. The disc diffusion assay was used to test the compounds for antibiotic activity on two bacteria species and their drug-resistant counterparts. The compounds displayed antibiotic activity towards the two non-drug-resistant bacteria. As for the drug-resistant organisms, only [Ru₂(2BUT)(DMF)₂(DPA)₂](BH₄)₄3 and 2, 2-dipyridylamine inhibited the growth of MRSA. Gel electrophoresis DNA cleavage studies showed that the ligands had no DNA cleaving properties while all the complexes denatured the bacterial DNA. Therefore, the complexes may have DNA nuclease activity towards the bacterial genomic material.

Tridentate imidazole-based Schiff base metal complexes: molecular docking, structural and biological studies

A novel Schiff base was synthesized by the condensation of imidazole-2-carboxaldehyde with l-histidine in an equimolar ratio. The prepared Schiff base was characterized by elemental analysis and spectral characterization techniques. It was then complexed with a series of 3-d metal(II) ions like manganese, iron, cobalt, nickel, copper and zinc. The coordination properties, nature of bonding and stability of the complexes were deduced from elemental analysis, IR, UV-vis, ¹H NMR, mass, electronic spectra, magnetic, conductivity and thermogravimetric analysis. IR studies support the tridentate behaviour of Schiff base as well as its coordination to the central metal ion through an azomethine nitrogen, deprotonated carboxylic oxygen and imidazole ring nitrogen atoms of histidine. The electronic spectra and magnetic moment data demonstrate that the complexes have an octahedral geometry, except zinc complex, which has a tetrahedral geometry. In vitro antimicrobial activity of the synthesized compounds has been shown to exhibit excellent antibacterial and antifungal activities. The antibacterial property of the prepared Schiff base was further confirmed by conducting a docking study of target proteins involved in the antibacterial mechanism.Communicated by Ramaswamy H. Sarma.

Synthesis of Mixed Ligand Ruthenium (II/III) Complexes and Their Antibacterial Evaluation on Drug-Resistant Bacterial Organisms

The potential antimicrobial properties of a tridentate polypyridyl ligand 4-butoxy-N,N-bis(pyridin-2-ylmethyl)aniline (BUT) 1 and its corresponding mixed ligand ruthenium complexes were investigated on drug-resistant and non-drug-resistant bacterial species. The ligand and its complexes were synthesized and successfully characterized by 1H NMR, UV/Vis, and FTIR spectra; ESI-MS; and magnetic susceptibility. Electronic spectra and magnetic susceptibility of these Ru(II)/(III) complexes suggest that they are of a low spin crystal field split, where the Ru(III) is a d5 and Ru(II) d6 low spin. These compounds were tested for antibacterial activity on two bacterial species: Staphylococcus aureus (S. aureus) and Klebsiella pneumoniae (K. pneumoniae), as well as their drug-resistant strains methicillin-resistant Staphylococcus aureus (MRSA) and multidrug resistant Klebsiella pneumoniae (MDR K. pneumoniae). All the compounds inhibited growth of the two non-drug-resistant bacteria and only one drug-resistant strain MRSA. However, only the ligands BUT and 2,2-dipyridylamine showed activity against MRSA, while all complexes did not show any antibacterial activity on MRSA. We observed large zones of inhibition for the Gram-positive S. aureus and MRSA bacteria, compared to the Gram-negative K. pneumoniae bacteria. DNA cleavage studies with gel electrophoresis showed denatured bacterial DNA on the gel from all the complexes, with the exception of the ligand, suggesting DNA nuclease activity of the complexes in the bacterial DNA.

Microwave assisted synthesis, characterization and biocidal activities of some new chelates of carbazole derived Schiff bases of cadmium and tin metals

This study is planned to report the advancement of green microwave approach in the fabrication of a new series of biologically potent (N^X, where X=O/S) donor Schiff bases and their cadmium(II) and tin(II) complexes. The ligands and their metal complexes have been characterized in terms of elemental analysis, molar ionic conductance, magnetic moment and spectral (IR, UV-Vis, NMR ((1)H, (119)Sn), FAB-mass, thermal and XRD) data. The data revealed that the ligands coordinated to the metal center via nitrogen and oxygen/sulfur atoms and form an octahedral arrangement of the ligands around central metal atom. All compounds were evaluated for their in vitro antimicrobial activities against two pathogenic bacteria Bacillus subtilis and Escherichia coli and two fungi Aspergillus niger and Aspergillus flavus by standard disc diffusion method. The discs were stored in an incubator at 37°C. The compounds were dissolved in DMF at 500 and 1000 ppm concentrations for screening biocidal activity. The compounds were dissolved in DMF to get the 100 and 200 ppm concentration of test solutions for screening fungicidal activity. The inhibition zone around each disc was measured (in mm) after 24 h and 96 h for biocidal and fungicidal activities respectively.

Synthesis, spectroscopic characterisation, DNA cleavage, superoxidase dismutase activity and antibacterial properties of some transition metal complexes of a novel bidentate Schiff base derived from isatin and 2-aminopyrimidine

Complexes of manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) with a Schiff base, formed by the condensation of isatin with 2-aminopyrimidine have been synthesised and characterised through elemental analysis, molar conductance measurements, magnetic susceptibility, IR, UV-Vis, (1)HNMR, FAB mass and EPR spectral studies. The spectral data revealed that the ligand acts as neutral bidentate, coordinating to the metal ion through the carbonyl oxygen and azomethine nitrogen. Molar conductance values adequately support the electrolytic nature of the complexes. On the basis of the above observations the complexes have been formulated as [M(ISAP)2]X2, where M=Mn(II), Co(II), Ni(II), Cu(II) and Zn(II); X=Cl, OAc; ISAP=2-[N-indole-2-one]aminopyrimidine. The ligand and copper(II) complex were subjected to X-ray diffraction studies. The DNA cleavage study was monitored by gel electrophoresis method. The superoxide dismutase (SOD) mimetic activities of the ligand and the metal complexes were checked using NBT assay. The in vitro antibacterial activity of the synthesized compounds has been tested against gram negative and gram positive bacteria.