Two cobalt(II) coordination compounds with 3-hydroxypyridine with thiocyanate or deprotonated bridging ligand, and comparison with isostructural analogs.

Two cobalt(II) coordination compounds with 3-hydroxypyridine, [Co(3-pyOH)4(NCS)2] (1) and [Co(3-pyOH)2(μ-3-pyO)2]n (2), were synthesised from aqueous solution and characterised by single-crystal X-ray diffraction, infrared spectroscopy, elemental analysis, and magnetic susceptibility measurements. Compound 1 is a discrete centrosymmetric complex in which the Co(II) ion adopts a slightly distorted octahedral N6 coordination environment formed by four neutral 3-pyOH ligands and two terminal N-bonded thiocyanate ligands. Compound 2 is a two-dimensional coordination polymer containing both neutral 3-pyOH and deprotonated μ-3-pyO- ligands, with the Co(II) ion in a distorted octahedral N2O4 donor environment. The crystal packing of both compounds is supported by hydrogen-bonding interactions and π-π stacking between pyridine rings. Hirshfeld surface analysis was used to evaluate the main close contacts contributing to the crystal packing. Infrared spectroscopy supports the structural assignments, particularly the presence of terminal N-bonded thiocyanate ligands in 1, while magnetic measurements indicate high-spin octahedral Co(II) centres in both compounds. The structures are compared with isostructural Ni(II), Mn(II) and Cd(II) coordination compounds.