2-Chloro-4-{(E)-[(4-chloro­phen­yl)imino]­meth­yl}phenol

In the title Schiff base compound, C13H9Cl2NO, the dihedral angle between the mean planes of the benzene rings is 10.20 (10)°. The crystal structure is stabilized by O—H⋯N hydrogen bonds and weak π–π stacking inter­actions [centroid–centroid distance = 3.757 (1) Å]

2-Hydr­oxy-5-nitro­benzaldehyde

The title compound, C7H5NO4, is essentially planar, with a maximum deviation from the mean plane of 0.0116 (11) Å for the hydr­oxy O atom. The mol­ecular and crystal structure are stabilized by intra- and inter­molecular inter­actions. An intra­molecular O—H⋯O hydrogen bond generates a six-membered ring, producing an S(6) ring motif. The C—H⋯O inter­actions result in the formation of C(5) chains and R 2 2(8) rings forming an approximately planar network parallel to (10). These planes are inter­connected through π–π inter­actions [centroid–centroid distance 3.582 (2) Å]

(E)-2-[(2,4-Dichloro­phen­yl)imino­meth­yl]benzene-1,4-diol monohydrate

The title compound, C13H9Cl2NO2·H2O, represents a Schiff base which adopts the phenol–imine tautomeric form in the solid state. The mol­ecule is approximately planar (r.m.s. deviation 0.0818 Å), and the dihedral angle between the two aromatic rings is 7.46 (12)°. An O—H⋯N inter­action generates an S(6) ring. In the crystal, mol­ecules are linked by inter­molecular O—H⋯O hydrogen bonds involving the solvent water mol­ecule, forming chains

(E)-2-[3-(Trifluoro­meth­yl)phenyl­imino­meth­yl]benzene-1,4-diol

In the title compound, C14H10F3NO2, the two benzene rings are oriented at a dihedral angle of 31.94 (14)°. An intra­molecular O—H⋯N hydrogen bond helps to stabilize the mol­ecular structure. In the crystal, inter­molecular O—H⋯O hydrogen bonding links the mol­ecules, forming chains running along the crystallographic a axis. The F atoms of the trifluoro­methyl group are disordered over two positions with refined site occupancies of 0.488 (5) and 0.512 (5)

(E)-2-[(3-Fluoro­phen­yl)imino­meth­yl]-4-(trifluoro­meth­oxy)phenol

The title compound, C14H9F4NO2, is a Schiff base which adopts the phenol–imine tautomeric form in the solid state. The H atom is located on the hydr­oxy O atom rather than on the N atom. This H atom is involved in a strong intra­molecular O—H⋯N hydrogen bond. The mol­ecule is almost planar, the angle between the benzene rings being 2.14 (13)°

(E)-2-[(2,4-Dichloro­phen­yl)imino­methyl]-6-methyl­phenol

The title compound, C14H11Cl2NO, is a Schiff base which adopts the phenol–imine tautomeric form in the solid state. There are two mol­ecules in the asymmetric unit. Head-to-tail π–π inter­actions [centroid-to-centroid distances of 3.682 (2), 3.708 (2), 3.904 (2) and 3.910 (2) Å] between adjacent mol­ecules produce two symmetry-independent infinite chains running along the b axis

4-(2,3-Dihydroxybenzyl­ideneamino)-3-methyl-1H-1,2,4-triazol-5(4H)-one

All the non-H atoms of the title compound, C10H10N4O3, are almost coplanar, the maximum deviation from planarity being 0.065 (3) Å. The dihedral angle between the aromatic rings is 1.66 (6)°. The mol­ecule adopts the enol–imine tautomeric form with an intra­molecular hydrogen-bonding inter­action between the Schiff base N atom and the hydr­oxy group. In the crystal, inter­molecular N—H⋯O and O—H⋯O hydrogen bonds link the mol­ecules into a three-dimensional network

3-Meth­oxy-2-[(E)-(4-meth­oxy­phen­yl)imino­meth­yl]phenol

The title compound, C15H15NO3, adopts the enol–imine tautomeric form. The two rings are twisted with respect to each other, making a dihedral angle of 44.08 (5)°. The 3-methoxy-2-[(E)-(4-methoxyphenyl)-iminomethyl]phenol unit is almost planar, the largest deviation from the mean plane being 0.047 (2) Å. Such a planar conformation might be related to the occurrence of an intra­molecular O—H⋯N hydrogen bond. In the crystal, inter­molecular C—H⋯O hydrogen bonds link the mol­ecules into sheets parallel to (010). These sheets are inter­connected by weak C—H⋯π inter­actions