Oxoanion influences on the self-assembly of cationic co-ordination complex polymers of the nickel(II)-di-4-pyridylamine family

Hydrothermal reactions of Ni^II, di-4-pyridylamine (dpa) and the appropriate oxide yield materials of the Ni^II-organodiamine-EO₄^2- family. Specifically, reaction of NiCl₂·6H₂O, dpa, and MoO₃ in water at 120°C yielded [Ni(dpa)₂(MoO₄)] 1, while the reaction of NiSO₄·6H₂O and dpa in water at 120°C gave [Ni(dpa)(SO₄)(H₂O)]·2H₂O 2. The structures reveal the dramatic influence of the anion identity and ligation modes in the {Ni(dpa)_n}_n²ⁿ⁺ substructure. The structure of 1 is constructed from two motifs, two-dimensional {Ni(dpa)}_n²ⁿ⁺ sheets and one-dimensional {NiMoO₄}_n chains, to produce a three-dimensional covalently linked framework. In contrast, the {Ni(dpa)}_n²ⁿ⁺ substructure of 2 is three-dimensional, with co-ordinated SO₄^2- and aqua ligands projecting into channels formed by the {Ni(dpa)}_n²ⁿ⁺ framework. The void is reduced through the common characteristic of interpenetration, such that the structure of 2 exhibits two independent three-dimensional frameworks.