4-Phenylpyridinium betaine of squaric acid

The title compound, 4-phenylpyridinium-3-squarate, C15H9NO3, exhibits an interplanar angle between the pyridinium and squarate rings of 0.6 (1)degrees. It displays a dipolar electronic ground-state structure, with a positively charged pyridinium fragment and a negatively charged squarate moiety. In the molecule, the two aromatic rings are twisted by 31.6 (1)degrees. The bond lengths within the squarate system represent average values for the two possible resonance structures, with a central typical carbonyl bond [1.203 (2) angstrom] flanked by two longer 'semicarbonyl' bonds of lengths 1.228 (2) and 1.221 (2) angstrom.