N'-(4-Diethyl-amino-2-hy-droxy-benzyl-idene)-4-methyl-benzohydrazide.

The title compound, C(19)H(23)N(3)O(2), was prepared by condensing 4-diethyl-amino-2-hy-droxy-benzaldehyde and 4-methyl-benzo-hydrazide in methanol. The asymmetric unit contains two independent mol-ecules in which the two benzene rings make dihedral angles of 30.3 (3) and 18.9 (3)°. Intra-molecular O-H⋯N hydrogen bonds are observed in both mol-ecules. The crystal structure is stabilized by N-H⋯O hydrogen bonds, which form chains along the a axis.

2-Hy-droxy-N'-(5-hy-droxy-2-nitro-benzyl-idene)-3-methyl-benzohydrazide.

The title compound, C(15)H(13)N(3)O(5), was prepared by condensing 5-hy-droxy-2-nitro-benzaldehyde and 2-hy-droxy-3-methyl-benzohydrazide in methanol. The two benzene rings make a dihedral angle of 3.9 (3)°. An intra-molecular O-H⋯O hydrogen bond is observed. The crystal structure is stabilized by inter-molecular O-H⋯O and N-H⋯O hydrogen bonds, and C-H⋯O and π-π inter-actions [centroid-centroid distances = 3.5658 (17)-3.9287 (19) Å].

2-Hy-droxy-N'-(4-hy-droxy-benzyl-idene)-3-methyl-benzohydrazide.

The title compound, C(15)H(14)N(2)O(3), was prepared by condensing 4-hy-droxy-benzaldehyde and 2-hy-droxy-3-methyl-benzo-hydra-zide in methanol. The two benzene rings make a dihedral angle of 19.03 (11)°. An intra-molecular O-H⋯O hydrogen bond is observed. The crystal structure is stabilized by inter-molecular O-H⋯O and N-H⋯O hydrogen bonds and C-H⋯O inter-actions, which lead to the formation of a three-dimensional network.

N'-(3-Eth-oxy-2-hy-droxy-benzyl-idene)-2-hy-droxy-3-methyl-benzohydrazide.

The title compound, C(17)H(18)N(2)O(4), crystallizes with two independent mol-ecules in the asymmetric unit. The two benzene rings in each mol-ecule make dihedral angles of 7.6 (3) and 3.9 (3)°. Intra-molecular O-H⋯N and O-H⋯O hydrogen bonds are present in each mol-ecule. In the crystal, N-H⋯O hydrogen bonds link the mol-ecules into chains propagating in [010]. The are also a number of C-H⋯O and π-π inter-actions present [centroid-centroid distances = 3.874 (4) and 3.904 (3) Å], that result in the formation of a three-dimensional network.