Synthesis, spectoscopic, thermal, and mophological studies of metal-based complexes derived from the reaction of cinchonine with manganese(II), nickel(II), and zinc(II) ions

This work involved the meticulous synthesis of three metal-based complexes of the naturally occurring compound cinchonine (abbreviated as CN), which belongs to the Cinchona alkaloids family and exhibits potent antimalarial properties. Studying these metal-based complexes is crucial, as it enhances our understanding of cinchonine's biological characteristics. The CN complexes were carefully prepared by dissolving the CN ligand in methanol and the investigated Mn(II), Ni(II), and Zn(II) metal ions in deionized water. The chemical reactions were carried out at a controlled temperature of 70 °C, a 1:1 (CN to metal ion) stoichiometry, and a pH of approximately 8.5. These conditions yielded the desired CN-Mn, CN-Ni, and CN-Zn complexes, which were subsequently characterized using various physicochemical techniques. The comprehensive characterization provided detailed insights into the structural, thermal, and morphological properties of the complexes. The results indicate that the CN complexes with Mn(II), Ni(II), and Zn(II) can be represented by the formulas [MnCN(H2O)3Cl2], [NiCN(H2O)5]·Cl2·2H2O, and [ZnCN(H2O)5]·Cl2·4H2O, respectively. The IR spectral data suggests that the CN ligand coordinated with the Mn(II), Ni(II), and Zn(II) ions through the nitrogen lone pair electrons of the C=N group. The high-quality and well-focused TEM images demonstrate the complexes possessed a uniform and well-structured morphology. KEY WORDS: Cinchonine, Metal ions, Spectroscopic analyses, Thermal characterization, Electron microscopy Bull. Chem. Soc. Ethiop. 2025, 39(6), 1095-1108. DOI: https://dx.doi.org/10.4314/bcse.v39i6.6