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.

Three novel cobalt(II) complexes based on acetate and aminopyridine ligands were synthesized and characterized magnetically, structurally and spectrally where different position of amino substituents enables distinct supramolecular associations.Figure optionsDownload as PowerPoint slideHighlights
► Three coordination compounds of cobalt(II) acetate with 2-, 3- and 4-aminopyridine were synthesized.
► Two of the compounds possess cis- and one trans-distorted octahedral geometry around the Co center.
► Magnetic measurements reveal the 2+ ionic state of cobalt and paramagnetic behavior.
► IR spectral studies show differences in NH2 stretching region, ring and COO− stretching vibrations.