Three solvates of a bis-mesoionic fluorescent yellow pigment

p‐Phenylenebis(2‐oxo‐3‐phenyl‐1,2‐dihydropyrido[1,2‐a]pyrimidin‐5‐ium‐4‐olate), C34H22N4O4, is a bis‐mesoionic yellow pigment that shows fluorescence in the solid state. During a polymorph screening, single crystals of three solvates were grown and their crystal structures determined. Solvent‐free crystals were not obtained. A solvate with N‐methylpyrrolidone (NMP) and propan‐2‐ol, C34H22N4O4·2C5H9NO·C3H8O, (Ia), and an NMP trisolvate, C34H22N4O4·3C5H9NO, (Ib), crystallize with pigment molecules on inversion centres. The NMP/propan‐2‐ol mixed solvate (Ia) forms O—H...O hydrogen bonds between the different solvent molecules. In both structures, at least one of the solvent molecules is disordered. A third solvate structure, C34H22N4O4·0.5C5H9NO·C4H10O, (Ic), was obtained by crystallization from NMP and butan‐1‐ol. In this case, there are two symmetry‐independent pigment molecules, both situated on inversion centres. The solvent molecules are heavily disordered and their contribution to the scattering was suppressed. This solvate displays a channel structure, whereas the other two solvates form layer structures.