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<p>The synthesized ligand, <i>N</i>-(pyridine-2-ylmethyl)pyrazine-2-carboxamide (<b>L</b>), was employed to prepare Co(II) and Mn(II) coordination complexes. The cobalt complex, [Co(L)<sub>2</sub>CoCl<sub>3</sub>].(Et<sub>2</sub>O).(CH<sub>3</sub>OH) (<b>Co</b><sup><b>L</b></sup>), 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 <b>L</b> 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}<sub>n</sub> (<b>Mn</b><sup><b>L</b></sup>), crystallizes in the triclinic system and assembles into a polymeric chain through µ-chloride bridges and <b>L</b> 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 <b>L</b>. 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 <b>L</b> and its metal complexes were systematically evaluated. The free ligand <b>L</b> and the <b>Mn</b><sup><b>L</b></sup> 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.</p>

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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

  • 期刊论文

  • 发表日期：

    2025年9月1日

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  • Fatemeh Soleimani Ravandi,
  • Robabeh Alizadeh,
  • Vahid Amani,
  • Raziyeh Arabahmadi

摘要

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) (CoL), 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 (MnL), 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 MnL 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.