The title compound, C15H14N2O3, was prepared by condensing 4-hy­droxy­benzaldehyde and 2-hy­droxy-3-methyl­benzo­hydra­zide in methanol. The two benzene rings make a dihedral angle of 19.03 (11)°. An intra­molecular O—H⋯O hydrogen bond is observed. The crystal structure is stabilized by inter­molecular O—H⋯O and N—H⋯O hydrogen bonds and C—H⋯O inter­actions, which lead to the formation of a three-dimensional network.

The title compound, C17H18N2O4, crystallizes with two independent mol­ecules in the asymmetric unit. The two benzene rings in each mol­ecule make dihedral angles of 7.6 (3) and 3.9 (3)°. Intra­molecular O—H⋯N and O—H⋯O hydrogen bonds are present in each mol­ecule. In the crystal, N—H⋯O hydrogen bonds link the mol­ecules into chains propagating in [010]. The are also a number of C—H⋯O and π–π inter­actions present [centroid–centroid distances = 3.874 (4) and 3.904 (3) Å], that result in the formation of a three-dimensional network.

With a bis Schiff base N,N' ethylene bis(5 chlorosalicylideneimine) (H 2 L) and K 3 [Co(CN) 6 ], a novel cyanide bridged heteronuclear Co(III)-Mn(III) complex was prepared and characterized by elemen tal analysis, IR spectroscopy and X ray structure determination (CIF file CCDC no. 1029225). The complex crystallizes in the monoclinic space group P2 1 /c with unit cell dimensions a = 10.741 (2), b = 14.015(3), c = 15.074(3) Å, β = 94.237(2)°, V = 2263.0(8) Å 3 , Z = 2, R 1 = 0.0441, and wR 2 = 0.0999. Single crystal X ray diffraction analysis reveals that two [Mn(L)(OH 2 )] + units are linked through a [Co(CN) 6 ] 3-bridge, forming a trinuclear Mn-Co-Mn moiety. The Mn-Co-Mn moieties are further linked through K atoms to form a 1D chain. The chains are stacked through π···π interactions. The Mn and Co atoms are in octahedral coor dination, and the K atom is in square planar geometry.

The title compound, C15H13N3O5, was prepared by condensing 5-hy­droxy-2-nitro­benzaldehyde and 2-hy­droxy-3-methyl­benzohydrazide in methanol. The two benzene rings make a dihedral angle of 3.9 (3)°. An intra­molecular O—H⋯O hydrogen bond is observed. The crystal structure is stabilized by inter­molecular O—H⋯O and N—H⋯O hydrogen bonds, and C—H⋯O and π–π inter­actions [centroid–centroid distances = 3.5658 (17)–3.9287 (19) Å].

The title compound, C19H23N3O2, was prepared by condensing 4-diethyl­amino-2-hy­droxy­benzaldehyde and 4-methyl­benzo­hydrazide in methanol. The asymmetric unit contains two independent mol­ecules in which the two benzene rings make dihedral angles of 30.3 (3) and 18.9 (3)°. Intra­molecular O—H⋯N hydrogen bonds are observed in both mol­ecules. The crystal structure is stabilized by N—H⋯O hydrogen bonds, which form chains along the a axis.