Three new cobalt(II) carboxylates with 2-, 3- and 4-aminopyridine: Syntheses, structures and magnetic properties

Three coordination compounds of cobalt(II) acetate with 2-, 3- and 4-aminopyridine were obtained after dissolving Co(CH3COO)2·2H2O and Co(CH3COO)2·4H2O in different solutions of aminopyridines. All three products were characterized magnetically, structurally by single-crystal X-ray diffraction analysis and spectrally by FT-IR spectroscopy. The reaction of Co(CH3COO)2·2H2O with 2-aminopyridine (2-apy) results in the third known modification of a monomeric complex of [Co(O2CCH3)2(2-apy)2] (1) with cis-geometry of the ligands around the metal center. Dark red crystals of the complex, synthesized by the reaction of Co(CH3COO)2·4H2O and 3-aminopyridine (3-apy), result in coordination polymer with the formula {[Co(O2CCH3)2(3-apy)2]·H2O}n (2). Molecular structure of compound 2 consists of a zigzag chain where cobalt(II) ions are connected by 3-aminopyridine ligands. The red crystals, obtained by the reaction of Co(CH3COO)2·4H2O with 4-aminopyridine (4-apy), result in a monomeric complex [Co(O2CCH3)2(4-apy)2(H2O)2] (3) in which the ligands possess trans-geometry around the Co(II) ion. Non-covalent interactions including intra- and intermolecular hydrogen bonds and π–π interactions in the crystal structures of 1–3 is discussed.