Synthesis, structural elucidation, molecular modeling and antimicrobial studies of Mn(II), Co(II), Ni(II), and Cu(II) complexes containing NO donor bidentate Schiff base

Abstract

Solid complexes (1–4) of Schiff base ((o‐tolylimino)methyl)phenol (HL) with manganese(II), cobalt(II), nickel(II), and copper(II) were synthesized in methanol under reflux. Schiff base (HL) was synthesized through condensation reaction of 2‐hydroxybenzaldehyde with o‐toluidine. Ligand (HL) and synthesized complexes (1–4) were characterized by using different spectroscopic techniques (UV–visible, FTIR, 1H NMR, mass spectrometry, powder X‐ray diffractometer [XRD]), magnetic measurements, and thermal gravimetric analysis. Spectroscopic analysis demonstrated that ligand being bidentate, in all the complexes, coordinates with metals through the N atom of azomethine group and O atom of the hydroxyl group. Molecular ion peaks (m/z) appear in the mass spectra of complexes confirm the proposed stoichiometry. TGA data of complexes 1 and 2 exhibited water molecules coordinated with the central metal ions (Mn2+ and Co2+). Magnetic Susceptibility analysis of metal complexes proposed octahedral geometry for Mn(II) and Co(II) complexes. Conductivity analysis was in good agreement with non‐electrolyte nature of metal complexes. Global reactivity data exhibited that metal(II) complexes are soft as compared to HL. Moreover, frontier molecular orbital (FMO) findings revealed that among the metal complexes, [Mn(L)2(H2O)2] 1 was having large energy gap showing greater stability and less reactivity, while [Ni(L)2] 3 was found most reactive among all of them. Values of chemical reactivity descriptors obtained denoted that synthesized metal complexes can be proved as efficient biological candidates owing to their reactivity patterns. In vitro antibacterial and antifungal activity of complexes and ligand were evaluated against different strains of bacteria (Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, and Bacillus subtilis) and fungi (Candida albicans, Aspergillus niger, Trichoderma harzianum, and Aspergillus flavus) via disc diffusion method. The bacterial and fungal growth more efficiently inhibited by the use of metal complexes (1–4) than ((o‐tolylimino)methyl)phenol (HL).

Antifungal activity of Fe3O4@SiO2/Schiff-base/Cu(II) magnetic nanoparticles against pathogenic Candida species

“…The antifungal activity of various Schiff-base complexes of metal ions like Cu 12 , Co 13 , Zn 14 , Fe 15 , Mn 8 have been studied, among which Cu coordinated with Schiff-base ligands is a new potential antifungal agent to expand the explorations. The following reports are on the antifungal ability of Cu Schiff-base complex of 2-((E)-(2–hydroxyethylimino)methyl)-1-naptaphenol 9 , Cu(II) complexes of porphyrin core 13 , thiophene-derived Schiff base complex of Cu (II) 16 , antipyrine derived-Schiff base Cu complex 17 , Cu(II) complexes with terpene derivatives of ethylenediamine 18 , Cu(II) complex containing NO donor bidentate Schiff base 19 , thiazole Schiff base complex of Cu 20 , 4,6-dihydroxy-1,3-phenylenediethanone Schiff base complex of Cu derived from 21 , and Cu(II) complex of Schiff-base based on glycine and phenylalanine 19 .…”