The title compound, C(23)H(20)N(4)O, is a heterocyclic phenyl-hydrazone Schiff base with a pyrazole moiety. In the crystal, a variety of inter-actions occur, including N-H⋯π and π-π stacking between the phenyl ring of the phenyl-hydrazinyl group and its symmetry-generated equivalent [centroid-centroid distance = 3.6512 (7) Å].

In the title mol-ecule, C20H21N3O, the central pyrazole ring forms dihedral angles of 4.75 (9) and 49.11 (9)°, respectively, with the phenyl and methyl-substituted benzene rings. The dihedral angle between the phenyl and benzene rings is 51.76 (8)°. The amino group and carbonyl O atom are involved in an intra-molecular N-H⋯O hydrogen bond. In the crystal, π-π inter-actions are observed between ...

In the title compound C(14)H(17)N(3)O(2), the dihedral angle between the rings is 16.68 (13)°. Although the compound crystallizes in the keto form, the possibility of keto-enamine-enol-imine tautomerism is explained by a strong intra-molecular N-H⋯O hydrogen bond.

In the crystal of the title compound, C(15)H(11)ClN(2)O, the molecules are linked by C-H⋯O and weak C-H⋯π inter-actions. The chloro-phenyl and phenyl rings are twisted with respect to the central pyrazolone ring, making dihedral angles of 18.23 (8) and 8.35 (8)°, respectively. The N-N and C=O bond lengths are comparable to those reported for pyrazolone compounds.