New ionic polymeric compounds are synthesized by the reactions of alkali metal carbonates with 3,5-dinitro-2-pyridone (Hdnhp) in an aqueous-alcohol solution: Li(dnhp)(H2O)n (I), Na(dnhp)(H2O)n (II), K(dnhp)(H2O)n (III), and K(dnhp)(Hdnhp)n (IV). Their structures are determined by single-crystal X-ray diffraction analysis. Analysis of the structures of the synthesized compounds shows that an increase in the ionic radius of the alkali metal cation (Li−Na−K) results in a regular increase in the coordination number (5, 6, and 7/8, respectively) and a change in the polymeric architecture type: from one-dimensional polymeric chains in compounds I and II to framework structures in compounds III and IV. The stereochemically rigid 2-pyridonate ligand plays a key role in structure formation exhibiting a variable denticity and different coordination modes. Hydrogen bonds and π−π-stacking interactions provide an additional stabilization of the crystal packings in compounds I and II. The structures are compared with the earlier described rubidium and cesium polymers to trace the coordination behavior of the dnhp– anion in the alkali metal series.
Никифорова et al. (Thu,) studied this question.