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.

Synthesis of sulfonamide through an indirect method that avoids contamination of the product with no need for purification has been carried out using the indirect process. Here, we report the synthesis of a novel sulfonamide compound, ({4-nitrophenyl}sulfonyl)tryptophan (DNSPA) from 4-nitrobenzenesulphonylchloride and L-tryptophan precursors. The slow evaporation method was used to form single crystals of the named compound from methanolic solution. The compound was characterized by X-ray crystallographic analysis and spectroscopic methods (NMR, IR, mass spectrometry, and UV-vis). The sulfonamide N-H NMR signal at 8.07–8.09 ppm and S-N stretching vibration at 931 cm⁻¹ indicate the formation of the target compound. The compound crystallized in the monoclinic crystal system and P2₁ space group with four molecules of the compound in the asymmetric unit. Molecular aggregation in the crystal structure revealed a 12-molecule aggregate synthon sustained by O-H⋯O hydrogen bonds and stabilised by N-H⋯O intermolecular contacts. Experimental studies were complemented by DFT calculations at the B3LYP/6-311++G(d,p) level of theory. The computed structural and spectroscopic data are in good agreement with those obtained experimentally. The energies of interactions between the units making up the molecule were calculated. Molecular docking studies showed that DNSPA has a binding energy of −6.37 kcal/mol for E. coli DNA gyrase (5MMN) and −6.35 kcal/mol for COVID-19 main protease (6LU7).

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.