Hydrothermal synthesis, structural determination, and thermal properties of 2-D cobalt- and nickel-based coordination polymers incorporating pendant-arm 3-pyridinecarboxylate ligands

Hydrothermal synthesis has afforded a family of four coordination polymers containing divalent nickel or cobalt and pendant-arm pyridylcarboxylate ligands. Utilizing 3-pyridylacetic acid and appropriate metal precursors produced [M(3-pyrac)2(H2O)2] phases (M = Co (1); M = Ni (2)), while 3-pyridylpropionic acid generated [M(3-pyrprop)2(H2O)2] coordination polymers (M = Co (3); M = Ni (4)). Single crystal X-ray diffraction revealed that 1–4 all display discrete 2-D layers with (4,4)-topology, anchored via bridging 3-pyridylcarboxylate ligands bearing monodentate carboxylate termini. Intralamellar hydrogen bonding between the aquo ligands and unligated carboxylate oxygen atoms is observed within 1–4. The pseudo 3-D structures of 1–4 are further assembled via stacking of individual neutral layers by interlayer hydrogen bonding. Thermal properties are also discussed.