Spectroscopic characterization, DFT calculations, in vitro pharmacological potentials, and molecular docking studies of N, N, O-Schiff base and its trivalent metal complexes
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2024-02-29
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Abstract
In this study, trivalent metal complexes of the category: [M(L)(H2O)nCly] obtained from the interaction of
metal3+ ion salts with organic N, N, O-Schiff base (HL) (where: HL = 4-{(Z)-((2-{(E)-((2-hydroxyphenyl)methylidene)amino}ethyl)imino)methyl}-2-methoxyphenol; n, y = 1 or 2 and M = Ti(III), Fe(III), Ru(III), Cr(III) and
Al(III)) were synthesized and characterized viz molar conductance, FT-IR, and UV–Vis spectroscopies, elemental
analyses, thermal analyses (TGA and DTA), and UV–Vis spectroscopy, theoretical calculations. A distorted
octahedral structure around the metal ions was proposed based on the obtained experimental and calculated
data. Thermal examination of the complexes signposts the step-by-step disintegration to give the final decomposition product as metal oxides. Moreover, DFT calculations were executed utilizing the B3LYP/LANL2DZ
theory level, which revealed that the synthesized metal (III) complexes were more stable than the free ligand
(HL). The value of ΔE for HL is 4.60 eV while the related values for the complexes of Cr(III) (C1), Ru(III) (C2), Fe
(III) (C3), Al(III) (C4), and Ti(III) (C5) are respectively 2.59, 3.68, 3.15, 1.64, and 2.75 eV. Scavenging abilities of
DPPH and ABTS radicals by the test compounds revealed promising antioxidant behavior. It was observed that
the compounds are proficient DPPH radical scavengers in a dose-dependent configuration. Ru(III); IC50 = 1.69 ±
2.68 µM for DPPH and Ti(III); IC50 = 8.70 ± 2.78 µM for ABTS performed best. Similarly, the complexes
demonstrated higher antimicrobial activities compared to HL against the designated strains, while ciprofloxacin
acted as a standard antibiotic. Furthermore, the ligand and its most effective complexes C2 and C5 were docked
against the targets S. aureus DNA gyrase (2XCT), S. pneumoniae DNA gyrase (5BOD), and E. coli DNA gyrase
(5L3J). The binding sites were evaluated and the docking results showed that the studied molecules bind to the
targets through classical O—H…O and/or N—H…O hydrogen bonds, as well as via hydrophobic contacts.