Acridine 0.75-hydrate

The title compound, C ₁₃H ₉N·0.75H ₂O was obtained during a study of the polymorphic system of acridine, by slow evaporation from an ethanol-water solution. There are two acridine molecules (indicated by I and II, respectively) and one and a half water mol-ecules in the asymmetric unit. The half-mol-ecule of water is located on a crystallographic twofold axis. The crystal structure is built up from two threads of molecule II sewn together with water molecules through O-H⋯O and O-H⋯N hydrogen bonds from one side and with π-π interactions [centroid-centroid distance = 3.640 (3) and 3.7431 (3) Å] between overlapping molecules II on the other side. Molecule I is attached to this thread from both sides by C-H⋯O hydrogen bonds. The threads are connected to each other by π-π interactions [centroid-centroid distances = 3.582 (3) and 3.582 (3) Å] between the inner side of molecule I and stabilized by a C-H⋯π interaction on the other side of molecule I. This thread with rows of molecule I hanging on its sides is generated by translation perpendicular to the a axis.