Supramolecular cobalt(II)-pyridine-2,5-dicarboxylate complexes with isonicotinamide, 2-amino-3-methylpyridine and 2-amino-6-methylpyridine: Syntheses, crystal structures, spectroscopic, thermal and antimicrobial activity studies

The mer-[Co(pydca)(H2O)3(ina)]·H2O (1), (2a3mpyH)2[Co(pydca)2(H2O)2]·2H2O (2) and (2a6mpyH)2[Co(pydca)2(H2O)2]·2H2O (3) complexes (H2pydca: pyridine-2,5-dicarboxylic acid, ina: isonicotinamide, 2a3mpy = 2-amino-3-methylpyridine and 2a6mpy = 2-amino-6-methylpyridine) were synthesised and characterised by elemental analysis, magnetic and spectroscopic measurements (UV–Vis and IR spectra) and single crystal X-ray diffraction technique. The thermal behaviour of the complexes was also studied by simultaneous thermal analysis techniques (TG, DTG and DTA). In complex 1, Co(II) ion was coordinated by one bidentate pydca, one isonicotinamide and three aqua ligands to generate a CoN2O4 distorted octahedral geometry. Complexes 2 and 3 crystallise in the triclinic system and space group P 1 ¯ and the structures consist of one complex anion [Co(pydca)2(H2O)2]2−, two protonated aminomethylpyridinium cations, ampyH+ and two crystal water molecules. In the anions, the Co(II) ions have a distorted octahedral configuration and are coordinated by two bidentate pydca and two trans-aqua ligands. The pydca ligand is coordinated to the Co(II) by both the heterocyclic N atom and the adjacent carboxylate group O atom, creating a chelate ring, while protonated ampy ions behave as counter ion.