Structural elucidation, spectroscopic, and metallochromic studies of 2-(2-hydroxy phenyl)-1-H–benzimidazole complexes: Metal ions sensing, DNA binding, and antimicrobial activity evaluation

Fe(III) and Ni(II) imidazole-benzimidazole mixed-ligand complexes: synthesis, structural characterization, molecular docking, DFT studies, and evaluation of antimicrobial and anti-inflammatory activities

This work delves into the synthesis, characterization, and bioactivity of new metal complexes of imidazole (IM)-based and benzimidazole (BZ)-based ligands with Fe(III) and Ni(II) ions. Broad characterization techniques, including elemental analysis, IR spectroscopy, magnetic moment measurement, electronic spectral analysis, mass spectrometry, thermal analysis, and DFT calculations, confirmed the successful preparation of the complexes with a 1 : 1 : 1 (M : IM : BZ) stoichiometry. The NiBZI M and FeBZIM complexes possessed octahedral geometry, with one and two water molecules coordinated with Fe(III) and Ni(II), respectively. DFT calculations demonstrated that the reduction of the energy gap and increase in softness for the metal complexes resulted from metal coordination, enhancing the reactivity and biological activity of the complexes. The FeBZIM and NiBZIM complexes exhibited strong antimicrobial activity, with both complexes displaying improved efficacy towards Gram-positive and Gram-negative bacteria compared with their corresponding free ligands. Their activities were comparable to the standard antibiotic chloramphenicol. Furthermore, these complexes exhibited good antifungal activity towards Aspergillus niger and Candida albicans, surpassing that of the free ligands. MIC values also ensured enhanced antimicrobial activity of the metal complexes. Other than these properties, the complexes demonstrated significant anti-inflammatory activity, where the FeBZIM complex exhibited the highest activity, with an IC50 value closer to that of the reference drug. Molecular docking studies on the E. coli FabH-CoA complex (PDB ID: 1HNJ) and human cyclooxygenase-2 (COX-2) (PDB ID: 5IKT) revealed that the FeBZIM complex exhibited the highest binding affinity with the formation of several hydrogen bonds with key amino acid residues, suggesting a favorable antibacterial activity. Overall, the newly synthesized FeBZIM and NiBZIM complexes demonstrated immense potential as novel antimicrobial and anti-inflammatory drugs with enhanced efficacy compared with their free ligands.

Sensing of Co2+ and Cu2+ Ions Using Dimethylamino-functionalized Poly(azomethine-1,3,4-oxadiazole)s

The ability of OxT and OxFl azomethines to recognize metal ions in THF solutions was investigated using UV-vis absorption techniques. Various metal ions, including Cd2+, Hg2+, Co2+, Sn2+, Cu2+, Ni2+, Zn2+ and Ag+, were tested. The absorption spectra revealed two distinct π-π* transition bands in the 273-278 nm and 330-346 nm wavelength ranges. Additionally, OxFl displayed an absorption peak at 309 nm, attributed to the fluorene group. Spectral titrations were used to study the fluorescence behavior in the presence of these metal ions. The results showed significant quenching with Co2+ and Cu2+ ions, while other metal ions had minimal effects on the fluorescence intensity. The quenching mechanism was further analyzed using the Stern-Volmer and Lehrer equations, and the binding constants ( K b fl ) were calculated using the Benesi-Hildebrand relations. The results confirm that Co2+ has a 1:2 stoichiometry and Cu2+ has a 1:1 stoichiometry, indicating the strong affinity of OxFl and OxT for these ions. The negative values of ΔG (Gibbs free energy) suggest that complex formation occurs spontaneously at room temperature.

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.