The Synthesis, Properties, and Biological Action of Metal Complexes with Schiff Bases

Abstract

The following metal complexes of Schiff bases have been reported and characterised: 2-
furancarboxaldehyde and o-phenylenediamine (L1), and 2-thiophenecarboxaldehyde and 2-
aminothiophenol (HL2). The analyses were conducted using thermal analysis (TGA), elemental
analyses, infrared 1H NMR, solid reflectance, magnetic moment, and chemical analysis. The pH-
metric calculation of the ligand dissociation and metal-ligand stability constants was performed at
25 ◦C and an ionic strength of μ = 0.1 (1 M NaCl). A number of complexes with the formula
[M(L1)(H2O)2] have been identified.With M = Fe(III), Ni(II), Cu(II), n = 2-3, and y = 2-4, the
equation becomes (Cl)n·yH2 O) [M(L1)].X squaredWhere M is Co(II), Zn(II), or UO2(II), X is Cl,
AcO, or NO3, and y ranges from 1 to 3, M(L2)2 is the equation to be used.In the above equation, M
may be represented by Co(II), Ni(II), or Cu(II); X can be Cl, y can be between 0 and 2; and Zn(II)
can be represented by AcO, y can be zero; and [Fe(L2)2 ]Cl·2H2O and [UO2(HL2)2](NO3)2.
According to the molar conductance data, the HL2 chelates of Co(II), Ni(II), Cu(II), and Zn(II) are
not electrolytes, but the HL2 chelates of Fe(III) and UO2(II) are. Using infrared spectra, we can see
that L1 has a tetradentate coordination to the metal ions via the ONNO donor sites of azomethine-N
and furan-O, and that HL2 has a terdentate coordination through the SNS donor sites of
azomethine-N, thiophene-S, and thiol-S. Octahedral and tetrahedral geometrical structures are
determined from the magnetic and solid reflectance spectra of these complexes. According to the
chelates' thermal behaviour, the hydrated complexes undergo hydration-related molecular loss in the
first stage, followed by the decomposition of anions and ligand molecules in the following phases.
E*, ΔH*, ΔS*, and ΔG* are activation thermodynamic parameters that are computed from the
DrTG curves by using the Coats-Redfern technique. Antibacterial activity against bacterial species,
Pseudomonas aeruginosa, Staphylococcus Pyogones, and fungi (Candida) was also tested for in the
synthesised ligands compared to their metal complexes. The activity findings demonstrate that the
metal complexes exhibit superior antibacterial properties compared to the parent Schiff base ligand
against at least one bacterium species.