A tripodal Schiff base ligand, 2,4,6-Tris(4-carboxybenzimino)-1,3,5-triazine (MT) and its trinuclear Dy(III), Er(III), and Gd(III) complexes were synthesized. These were characterized using UV-visible, IR, ¹H, and ¹³C NMR spectroscopies, elemental analysis, and molar conductivity measurements. The spectral studies indicate that the ligand is hexadentate and coordinates to the Ln(III) ions through the oxygen atoms of the carboxylic group. The trinuclear complexes were characterized as being bridged by carboxylate anions to the Dy(III), Er(III), and Gd(III) salen centers and displaying a coordination number of six. Biological studies revealed that MT is more active against the test micro-organisms relative to the trinuclear complexes. Acute toxicity studies revealed that MT is safe and has a wide range of effective doses (ED₅₀). In vivo antimalarial studies indicate that MT could serve as an effective antimalarial agent since it has parasitemia inhibition of 84.02% at 50 mg/kg and 65.81% at 25 mg/kg, close to the value (87.22%) of the standard drug—Artesunate. Molecular docking simulation studies on the compounds against SARS-CoV-2 (6Y84) and E. coli DNA gyrase (5MMN) revealed effective binding interactions through multiple bonding modes. The binding energy calculated for Er(III)MT-6Y84 and Er(III)MT-5MMN complexes showed active molecules with the ability to inhibit SARS-CoV-2 and E. coli DNA gyrase.

N-(Benzothiazol-2-yl)-4-chlorobenzenesulphonamide (NBTCS) was synthesized by condensation reaction of 4-chlorobenzenesulphonyl chloride and 2-aminobenzothiazole in acetone under reflux. Neodymium(III) and thallium(III) complexes of the ligand were also synthesized. Both ligand and metal complexes were characterized using UV-Vis, IR, ¹H- and ¹³C-NMR spectroscopies, elemental analysis and molar conductance measurement. IR studies revealed that the ligand is tridentate and coordinates to the metal ions through nitrogen and oxygen atoms of the sulphonamide group and nitrogen atom attached to benzothiazole ring. The neodymium(III) complex displays a coordination number of eight while thallium(III) complex displays a coordination number of six. The ligand and its complexes were screened in vitro for their antibacterial activities against Escherichia coli strains (E. coli 6 and E. coli 13), Proteus species, Staphylococcus aureus and Pseudomonas aeruginosa using the agar well diffusion technique. The synthesized compounds were found to be more active against the microorganisms screened relative to ciprofloxacin, gentamicin and co-trimoxazole.

(1H-Indol-3-ylmethylene)-naphthalen-1-ylamine, INDNA was synthesized by the condensation of 1- naphthylamine with indole-3-carboxaldehyde. Additionally, the complexes of Os(VIII), Pd (II), Ni(II), Cr (III) and Fe(III) were synthesized. ESI-MS spectroscopic techniques, 1H and 13C NMR, UV-VIS, IR and elemental analysis were used to characterize the ligand and metal complexes. According to spectral data, INDNA binds as a bidentate ligand to the metal ions via the nitrogens in the imine and indole chains. The ligand to metal stoichiometry of the compounds is 2:1. The metal complexes exhibit tetrahedral geometry. The ligand and complexes were tested for their in vitro antibacterial activity against a range of microorganisms namely: Salmonella sp., Staphylococcus sp. (vancomycin resistant), Candida albicans, Klebisella sp. (pneumonia), sewage-producing sp., clinical sp., and typed sp. using agar well diffusion method. Compared to the ligand, the complexes were found to be more active against the tested bacteria. The antifungal activity of INDNA was enhanced on complexing with Pd (II) ion. The drug likenesses were also determined using molecular docking studies.

The reaction of N-morpholine-N′-benzoylthiourea (L: HBMOR) and lead(II) acetate gave a neutral, stable metal(II) complex of type ML2. The Pb(II) complex crystallized in a monoclinic crystal system with P21/n space group. The complex was further characterized by spectroscopic and microanalytic analyses. The solvent extraction behaviors of Pb(II) and Cu(II) ions were investigated in aqueous media containing HBMOR/CHCl3 as extracting reagents. The solvent extraction of Pb(II) and Cu(II) ions from solutions of varying pH, varying concentrations of mineral acids (HCl, HNO3 and H2SO4), varying concentrations of masking agents (EDTA, KCN and KH[C8H6O4]) and varying concentrations of salting-out agents (NaCl, Na2SO4, KNO3) in chloroform solutions of HBMOR were studied. Pb(II) and Cu(II) ions were quantitatively extracted at pH = 7 in 10 min (HCl = 0.01 M) and pH = 8 in 5 min (H2SO4 = 0.01 M), respectively. The Pb(II) ions were quantitatively extracted with minimal interference from EDTA (0.01 M), KCN (0.50 M), and potassium hydrogen phthalate (1.0 M), while the Cu (II) ions were extracted with EDTA (1.0 M), KCN (1.0 M) and potassium hydrogen phthalate (0.01 M). The order of increasing interference for the extraction of Pb(II) and Cu(II) ions was KCN > potassium hydrogen phthalate > EDTA. Sodium sulfate (0.01 M) in HCl enhanced the extraction of Pb(II) ions, while sodium chloride (0.50 M) in HCl enhanced the extraction of Cu(II) ions. pH0.5 values of 0.67 and 2.70 were obtained for Pb(II) and Cu(II) ions, respectively, indicating that the separation of the two metal ions is favorable with HBMOR.

Novel Schiff base ligand 1,5‐dimethyl‐4‐((1‐(3‐methyl‐5‐oxo‐1‐phenyl‐1,5‐dihydro‐4H‐pyrazol‐4‐ylidene)butyl)amino)‐2‐phenyl‐1,2‐dihydro‐3H‐pyrazol‐3‐one was synthesized by the condensation reaction between 4‐acylpyrazol‐5‐one and 4‐aminoantipyrine. Ni(II), Cu(II), Co(II), or Zn(II) complexes were synthesized by reactions of the ligand with respective metal chlorides. The ligand and complexes were characterized by conventional spectroscopic techniques: UV–Visible, FTIR, mass spec, ¹ H and ¹³ C NMR, and single‐crystal XRD analysis. The crystal system and space group of the ligand are monoclinic and P21/c , respectively. Computational studies (DFT and molecular docking) were employed to supplement the experimental findings and predict possible applications of the novel Schiff base. DFT studies indicate that two ligands each coordinate to the metal(II) center in a bidentate manner, resulting in a pseudo‐tetrahedral geometry. The Schiff base ligand exhibited tautomerism where the amine‐one was more stable than the imine‐ol. Molecular docking studies indicate that the Ni(II) complex showed a significant binding affinity and the best binding interaction with the Mycobacterium tuberculosis enoyl acyl carrier protein reductase (ENR) target enzyme. This suggests that binding to these specific proteins might lead to the mechanism of action of the evaluated antibacterial property.