X-ray Studies, Spectroscopic Characterization, and Biological Evaluation of Mixed-Valance Co(II)/(III) and µ-Chloride Bridged Mn(II) Carboxamide Complexes: Antioxidant and Antibacterial Properties

چکیده مقاله

The synthesized ligand, N-(pyridine-2-ylmethyl)pyrazine-2-carboxamide (L), was employed to prepare Co(II) and Mn(II) coordination complexes. The cobalt complex, [Co(L)₂CoCl₃].(Et₂O).(CH₃OH) (Co^L), crystallizes in the monoclinic system and contains a mixed-valence binuclear unit. In this structure, the Co(II) center adopts a distorted octahedral geometry, which is coordinated by two L ligands. Meanwhile, the Co(III) center exhibits a distorted tetrahedral geometry, which is coordinated by three chloride ligands and one nitrogen atom from a bridging pyrazine moiety. In contrast, the manganese(II) complex, {[Mn(L)](µ-Cl)Cl}_n (Mn^L), crystallizes in the triclinic system and assembles into a polymeric chain through µ-chloride bridges and L ligands, which act as asymmetric linkers. Each Mn(II) ion adopts a distorted octahedral geometry with one terminal and two bridging chloride ions, and coordinates through the pyridine, amide, and pyrazine donor sites of L. Hydrogen-bonding interactions play a key role in the crystal packing of both complexes. The structures of both complexes were thoroughly characterized by single crystal X-ray diffraction method, elemental analysis, FT-IR, and UV–Vis spectroscopy. Furthermore, the antioxidant and antibacterial properties of L and its metal complexes were systematically evaluated. The free ligand L and the Mn^L complex exhibited strong radical-scavenging activity, with inhibition percentages exceeding 80%. Antibacterial studies revealed that the metal complexes exhibited better activity than the free ligand. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2025.