| Summary: | The 6-oxonicotinate (6-Onic) salts of a one-dimensional cationic cobalt(II) or nickel(II) coordination polymers with 4,4′-bipyridine (4,4′-bpy), namely {[Co(4,4′-bpy)(H<sub>2</sub>O)<sub>4</sub>](6-Onic)<sub>2</sub>·2H<sub>2</sub>O}<i><sub>n</sub></i> (<b>1</b>) and {[Ni(4,4′-bpy)(H<sub>2</sub>O)<sub>4</sub>](6-Onic)<sub>2</sub>·2H<sub>2</sub>O}<i><sub>n</sub></i> (<b>2</b>), were prepared hydrothermally by reactions of cobalt(II) nitrate hexahydrate or nickel(II) nitrate hexahydrate, respectively, 6-hydroxynicotinic acid and 4,4′-bipyridine in a mixture of ethanol and water. In the hydrogen-bonded frameworks of <b>1</b> and <b>2</b>, the one-dimensional polymeric chains of {[M(4,4′-bpy)(H<sub>2</sub>O)<sub>4</sub>]<sup>2+</sup>}<i><sub>n</sub></i> (M = Co, Ni), the 6-oxonicotinate anions and the lattice water molecules were assembled via strong intermolecular O–H···O and N–H···O hydrogen bonds and <i>π</i>–<i>π</i> interactions, leading to the formation of the representative hydrogen-bond ring motifs: trimeric <i>R</i><sup>2</sup><sub>3</sub>(10) motif, the centrosymmetric tetrameric <i>R</i><sup>2</sup><sub>4</sub>(8) and <i>R</i><sup>2</sup><sub>4</sub>(12) motifs and the pentameric <i>R</i><sup>4</sup><sub>5</sub>(12) motif. The isostructural coordination polymers <b>1</b> and <b>2 </b>exhibited a different electrochemical behavior, as observed by cyclic voltammetry, which can be attributed to the nature of the metal ions (cobalt(II) vs. nickel(II)).
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