The title compounds, 2-(4-methylphenyl)-1H-perimidine hemihydrate (1, C18H14N2·0.5H2O) and 1-methyl-2-(4-methylphenyl)-1H-perimidine (2, C19H16N2), were prepared and characterized by 1H NMR and single-crystal X-ray diffraction. The organic mol-ecule of the hemihydrate lies on a twofold rotation axis while the water mol-ecule lies on the inter-section 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 mol-ecule as well as the CH3 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-methyl-ated 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, mol-ecules of perimidine 2 are held together only by C-H⋯π contacts while the parent perimidine 1 does not exhibit this type of inter-action. Its crystal packing is established by inter-molecular N-H⋯O hydrogen bonds with the solvent water mol-ecules and additionally stabilized by π-π stacking.
Keywords: NMR study; crystal structure; hydrogen bonding; perimidine; π–π stacking.
© Kalle et al. 2022.