N-H...N and C-H...pi interactions in 4-amino-3-methyl-5-(p-tolyl)-4H-1,2,4-triazole and 4-amino-3-methyl-5-phenyl-4H-1,2,4-triazole.

The title compounds, C10H12N4, (I), and C9H10N4, (II), have been synthesized and characterized both spectroscopically and structurally. The dihedral angles between the triazole and benzene ring planes are 26.59 (9) and 42.34 (2) degrees, respectively. In (I), molecules are linked principally by N-H...N hydrogen bonds involving the amino NH2 group and a triazole N atom, forming R(4)4(20) and R(2)4(10) rings which link to give a three-dimensional network of molecules. The hydrogen bonding is supported by two different C-H...pi interactions from the tolyl ring to either a triazole ring or a tolyl ring in neighboring molecules. In (II), intermolecular hydrogen bonds and C-H...pi interactions produce R(3)4(15) and R(4)4(21) rings.