Syntheses and crystal structures of 2-(p-tol­yl)-1H-perimidine hemihydrate and 1-methyl-2-(p-tol­yl)-1H-perimidine

The title compounds, 2-(4-methylphenyl)-1H-perimidine hemihydrate (1, C(18)H(14)N(2)·0.5H(2)O) and 1-methyl-2-(4-methylphenyl)-1H-perimidine (2, C(19)H(16)N(2)), were prepared and characterized by (1)H NMR and single-crystal X-ray diffraction. The organic mol­ecule of the hemihydrate lies on a twofold rotation axis while the water mol­ecule lies on the inter­section of three twofold rotation axes (point group symmetry 222). As a consequence, the hydrogen atoms that are part of the N—H group and the water mol­ecule as well as the CH(3) group of the p-tolyl ring are disordered over two positions. In compound 1, the perimidine and the 2-aryl rings are slightly twisted while its N-methyl­ated derivative 2 has a more distorted conformation because of the steric repulsion between the N-methyl group and the 2-aryl ring. In the crystal structures, mol­ecules of perimidine 2 are held together only by C—H⋯π contacts while the parent perimidine 1 does not exhibit this type of inter­action. Its crystal packing is established by inter­molecular N—H⋯O hydrogen bonds with the solvent water mol­ecules and additionally stabilized by π–π stacking.