Isomorphic oxamate derivatives triple mesocates: From the synthesis to antibacterial activities

• Published in: Journal of molecular structure 2025-01, p.141272, Article 141272
• Main Authors: Francescon, Jeane E., de J Pfau, Sâmella C., Borth, Ketlyn W., Marinho, Maria V., Pedroso, Emerson F., Giese, Siddhartha O.K., Pereira, Cynthia L.M., Miorim, Avany J.F., Maciel, Giselle M., Hughes, David L., Cano, Joan, Julve, Miguel, Stumpf, Humberto O., Simões, Tatiana R.G.
• Format: Article
• Language: English
• Subjects: Antibacterial activities; Dinuclear complexes; Mesocates; Molecular magnetism; Oxamate; Transition metal ions
• ISSN: 0022-2860
• DOI: 10.1016/j.molstruc.2024.141272

•Four homodinuclear triple mesocates containing oxamate ligand have been synthesized.•Magnetic measurements reveal a very weak ferromagnetic interaction between manganese(II) ions.•The ferromagnetic interaction is most likely masked by the zero-field splitting effects in the case of Co(II), Ni(II) and Fe(II) compounds•The four complexes showed antibacterial activity against Staphylococcus aureus.•The antibacterial properties against S. aureus were demonstrated by complexes with Mn(II) and Fe(II). Four homodinuclear triple mesocates of general formula (PPh4)2[M2(H2mpba)3]·2DMSO·4H2O (M = Co(II) (1), Ni(II) (2), Mn(II) (3) and Fe(II) (4), H4mpba = N,N’-1,3-phenylenebis(oxamic acid), PPh4+ = tetraphenylphosphonium and DMSO = dimethyl sulfoxide) have been synthesized. Their crystal structures determined by single-crystal X-ray diffraction. 1-4 are isostructural dinuclear compounds that crystallize in the space group C2/c with very close unit cell metrics, having in common the presence of [M2(H2mpba)3]2– mesocate entities whose charge is balanced by PPh4+ cations. Each metal ion in 1-4 is surrounded by six oxygen atoms from three bidentate monoprotonated oxamate groups in a somewhat distorted octahedral surrounding. The H2mpba2− ligands in 1-4 exhibit the bis-bidentate coordination mode, each monoprotonated oxamate fragment acting as a bidentate donor toward a metal ion through the amide-oxygen and one of the two carboxylate oxygen atoms. The values of the intramolecular metal-metal separation cover the range 6.10-6.74 Å. Hydrogen bonds between the mesocates lead to a zigzag-shaped supramolecular chain. Variable-temperature magnetic susceptibility data were carried out for 1-4 in the temperature range 4.0-300 K. A very weak ferromagnetic interaction between the metal center is observed for 3. In contrast, it is most likely masked by the zero-field splitting effects in the case of 1, 2, and 4. Although antibacterial activity against Escherichia coli (ATCC 25922) was observed only for 1 (MIC = 32 µg/mL), all four complexes showed antibacterial activity against Staphylococcus aureus (ATCC 6538) with MIC values of 32 µg/mL (1 and 3) and 64 µg/mL (2 and 4). The antibacterial properties against S. aureus were demonstrated by complexes with Mn(II) and Fe(II), with MBC of 64 (3) and 128 µg/mL (4), which leads to a possible investigation of the mechanism of these compounds against Gram-positive bacteria. In this contribution, we developed a family of homodinuclear tripl