Coordination compounds of some transition metal ions with new Schiff base ligand derived from dibenzoyl methane. Structural characterization, thermal behavior, molecular structure, antimicrobial, anticancer activity and molecular docking studies

Abstract

Series of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes were prepared with tetradentate Schiff base ligand derived by condensation of 2‐aminophenol with dibenzoylmethane. The novel Schiff base H2L (2–2′‐((1Z,1Z’)‐(1,3‐diphenyl propane‐1,3 diylidene) bis (azanylylidene) diphenol) and its binary metal complexes were characterized by physicochemical procedures i.e. elemental analysis, FT‐IR, UV–Vis, thermal analyses (TGA/DTG), mass spectrometry, magnetic susceptibility and conductometric measurements. On the basis of these studies, an octahedral geometry for all these complexes was proposed expect Ni(II) complex which had tetrahedral geometry. Molar conductivity values revealed that the complexes were electrolytes except Mn(II), Zn(II) and Cd(II) complexes were non electrolytes. The ligand bound to the metal ions via two azomethine N and two phenolic OH as indicated from the IR and 1H NMR spectral study. The molecular and electronic structures of H2L and its zinc complex were optimized theoretically and the quantum chemical parameters were calculated. The antimicrobial activity against a number of bacterial organisms as Streptococcus pneumonia, Bacillus Subtilis, Pseudomonas aeruginosa and Escherichia coli and fungi as Aspergillus fumigates, Syncephalastrum racemosum, Geotricum candidum and Candida albicans by disk diffusion method were screened for the Schiff base and its complexes. The Cd(II) complex has potent antimicrobial activity. Anticancer activity of the Schiff base ligand and its metal complexes were evaluated in human cancer (MCF‐7 cells viability). The Cr(III) complex exhibited higher activity than other complexes and ligand. Molecular docking was used to predict the binding between Schiff base ligand (H2L) and its Zn(II) complex and the receptors of RNA of amikacin antibiotic (4P20) and human‐DNA‐Topo I complex (1SC7). The docking study provided useful structural information for inhibition studies.

Inner metal complexes of tetradentate Schiff base: Synthesis, characterization, biological activity and molecular docking studies

“…The FT‐IR spectrum of the ligand shows a strong band at ca 1617 cm −1 which is attributed to ν(HC═N). The shift of this peak for the complexes to higher frequency in the range 1651–1656 cm −1 is an indication of the coordination of the nitrogen atom of HC═N group to the metal ion in the complexes . As expected, for the complexes, this is observed due to possible donation of the lone pair electron density towards the metal ion and makes strong evidence for the coordination of HC═N through nitrogen to the metal ions.…”

“…New peaks observed for the metal complexes at 430–476 and 529–580 cm −1 , assigned to M─N and M─O, respectively, provide additional confirmation for coordination of the oxygen atom of phenolic group and the imino group of the ligand with the metal ions . The ν(M─O) stretching vibrations of coordinated water attached to metal ions are found at 529–580 cm −1 for the complexes . The FT‐IR spectral data of ligand and its metal complexes are summarized in Table .…”

“…The antimicrobial activity of the complexes was determined using a modified Kirby–Bauer disc diffusion method . An amount of 100 μl of the test bacteria or fungi was added to 10 ml of fresh media until cultures reached a count of approximately 10 8 cells ml −1 for bacteria and 10 5 cells ml −1 for fungi .…”

“…Schiff bases are unique compounds due to the possibility of easily varying fragments at the exocyclic C═N bond, which allows exploring such important aspects as tautomerism, conformational equilibria, acid–base and donor–acceptor properties, etc. But, probably, the most important property of azomethines is their high complex‐forming ability . The formation of macrocyclic complexes depends significantly on the dimension of internal cavities, the rigidity of the macrocycles, the nature of its donor atoms and the complexing properties of the anion involved in the coordination .…”

Synthesis, characterization of Schiff base metal complexes and their biological investigation

“…Schiff bases are important due to their ability to stabilize metal ions of various oxidation states, participation in numerous catalytic and industrial applications and broad spectrum biological activities . The formation of stable complexes with metal ions is due to nitrogen lone pair of electrons of azomethine (−N = CH) bonding in their structure . These stable complexes play a prominent role in many important biological processes, supramolecular chemistry, bioinorganic and molecular magnetism .…”