2,9-Dimethyl-1,10-phenanthrolin-1-ium (6-carboxy-4-hydroxypyridine-2-carboxylato-κ<sup>3</sup><i>O</i><sup>2</sup>,<i>N</i>,<i>O</i><sup>6</sup>)(4-hydroxypyridine-2,6-dicarboxylato-κ<sup>3</sup><i>O</i><sup>2</sup>,<i>N</i>,<i>O</i><sup>6</sup>)nickelate(II) 2.35-hydrate: a proton-transfer compound
Acta crystallographica. Section E