N′-[(E)-2-Hy­droxy-5-meth­oxy­benzyl­idene]-2-meth­oxy­benzohydrazide

The mol­ecule of the title compound, C₁₆H₁₆N₂O₄, adopts an E conformation about the azomethine C=N double bond. The dihedral angle formed by the benzene rings is 18.88 (9)°. The mol­ecular conformation is stabilized by an intra­molecular O—H...N hydrogen bond, which forms an S(6) ring. In the crystal, the mol­ecules are linked into chains parallel to [001] by N—H...O hydrogen bonds. The chains are further connected into a three-dimensional network by π–π stacking inter­actions with centroid–centroid distances of 3.6538 (10) and 3.8995 (11) Å.

N′-[(E)-2,3-Dihy­droxy­benzyl­idene]-2-meth­oxy­benzohydrazide

The title compound, C₁₅H₁₄N₂O₄ adopts an E conformation about the azomethine double bond. Intra­molecular N—H...O and O—H...N hydrogen bonds generate S(6) rings and help to establish the molecular conformation. The dihedral angle between the benzene rings is 17.84 (10)°. In the crystal, mol­ecules are linked by O—H...O and C—H...O hydrogen bonds into a two-dimensional network with a herring-bone pattern arranged parallel to the bc plane.

3-(2-Ethyl-2-phenyl­hydrazin-1-yl­idene)indolin-2-one

In the title compound, C₁₆H₁₅N₃O, the dihedral angle between the indole ring system (r.m.s. deviation = 0.020 Å) and the phenyl ring is 14.49 (9)°. The mol­ecular conformation is supported by an intra­molecular C—H...O inter­action, which closes an S(7) ring. In the crystal, inversion dimers linked by pairs of N—H...O hydrogen bonds generate R₂²(8) loops.

N′-(3-Chloro­benzyl­idene)-4-hy­droxy­benzohydrazide

The mol­ecule of the title compound, C₁₄H₁₁ClN₂O₂ adopts an E conformation of the azomethine double bond and the dihedral angle between the benzene rings is 38.96 (13)°. In the crystal, mol­ecules are linked by N—H...O and O—H...O (with the ketone O atom as acceptor) and C—H...O (with the hy­droxy O atom as acceptor) hydrogen bonds, forming a three-dimensional network.