Synthesis, characterization and biological studies of pyrazole-linked Schiff bases and their copper( <scp>ii</scp> ) complexes as potential therapeutics

The novel pyrazole-linked Schiff base-derived Cu(ii) complexes were prepared, characterized, and evaluated for their biological potential. Single-crystal X-ray diffraction, UV-visible, FT-IR, NMR, EPR spectroscopy, mass spectrometry, and SEM-EDX techniques have been utilized for establishing the chemical structures of the compounds. The results of the single-crystal X-ray diffraction study of complex 4c disclosed that the prepared copper(ii) complexes possess a square planar geometry. Antimalarial screening against <i>P. falciparum</i> revealed that the ligand 3d and copper complexes 4a-d are more effective, with percentage suppression ranging from 90% to 100%, as determined by the RBC haemolysis assay. Compound 3d exhibited the highest selectivity index (SI = 18.38), followed by 3e (SI = 9.48) and 4d (SI = 6.02). Furthermore, molecular docking simulations were performed on newly prepared ligands and their copper(ii) complexes, which support their potential as effective antimalarial agents. An anticancer evaluation study revealed that compound 4b exhibited remarkable anticancer efficacy with the highest selectivity (SI = 13.48) towards A549 cells, outperforming the reference drugs Cisplatin, Carboplatin, and Dexamethasone. It was observed that complexation with copper ions results in increased selectivity for A549 cells and decreased cytotoxicity towards Vero cells. Moreover, compound 4e displayed the highest antibacterial potential with an MIC value of 0.02 mg mL^-1 against <i>B. subtilis</i>.