2-(3-Benzoyl-1-pyridinio)-3,4-dioxo-cyclobutenolate.

The title compound, C16H9NO4, also known as the 3-benzoylpyridinium betaine of squaric acid, exhibits 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 56.03 (2)° relative to one another. The three-dimensional packing of the molecules is stabilized by C—H··O· short contacts. [ABSTRACT FROM AUTHOR]