Crystal structures of salen-type ligands 2-[(1E)-({1-(3-chloro-phen-yl)-2-[(E)-(2-hy-droxy-benzyl-idene)amino]-prop-yl}imino)-meth-yl]phenol and 2-[(1E)-({1-(4-chloro-phen-yl)-2-[(E)-(2-hy-droxy-benzyl-idene)amino]-prop-yl}imino)-meth-yl]phenol.

The title compounds, C23H21ClN2O2, differ from each other only by the position of the Cl atom on the corresponding benzene ring: meta relative to the central sp3 C atom for (I) and para for (II). In (I), the hy-droxy-phenyl rings are almost parallel, the dihedral angle between the mean planes being 9.2 (2)°, but in (II), the relative position of the ring is different, characterized by a dihedral angle of 48.5 (1)°. Compound (I) features intra-molecular O-H⋯N and inter-molecular C-H⋯O hydrogen bonds, while in (II), intra-molecular O-H⋯N, C-H⋯N hydrogen bonds and weak inter-molecular C-H⋯π inter-actions are observed. Compound (I) was refined as an inversion twin.

Crystal structure of isobutyl 4-(2-chloro-phen-yl)-5-cyano-6-{(E)-[(di-methyl-amino)-methyl-idene]amino}-2-methyl-4H-pyran-3-carboxyl-ate.

In the title compound, C21H24ClN3O3, the dihedral angle between the pyran ring (r.m.s. deviation = 0.037 Å) and the chloro-benzene ring is 88.56 (14)°. In the crystal, the mol-ecules are linked by C-H⋯O inter-actions, generating C(7) (001) chains.

Crystal structure of (E)-1-([1,1'-biphen-yl]-4-yl)-3-(3-nitro-phen-yl)prop-2-en-1-one.

In the title compound, C21H15NO3, the mol-ecule has an E conformation about the C=C bond, and the C-C=C-C torsion angle is -178.24 (18)°. In the mol-ecule, the planes of the terminal rings are twisted by an angle of 42.19 (10)°, while the biphenyl part is not planar, with a dihedral angle between the rings of 39.2 (1)°. The dihedral angle between the nitro-phenyl ring and the inner benzene ring is 5.56 (9)°. The 3-nitro group is approximately coplanar with the benzene ring to which it is attached [O-N-C-C = 0.1 (3)°]. In the crystal, mol-ecules are linked via C-H⋯π inter-actions, involving the terminal benzene rings, forming corrugated layers parallel to (100).

Crystal structure of (E)-1-(4'-meth-oxy-[1,1'-biphen-yl]-4-yl)-3-(3-nitro-phen-yl)prop-2-en-1-one.

The title compound, C22H17NO4, crystallizes with two independent mol-ecules (A and B) in the asymmetric unit. Each mol-ecule exists as an E isomer with C-C=C-C torsion angles of -175.69 (17) and -178.41 (17)° in A and B, respectively. In mol-ecule A, the planes of the terminal benzene rings are twisted by an angle of 26.67 (10)°, while the biphenyl unit is non-planar, the dihedral angle between the rings being 30.81 (10)°. The dihedral angle between the nitro-phenyl ring and the inner phenyl ring is 6.50 (9)°. The corresponding values in mol-ecule B are 60.61 (9), 31.07 (8) and 31.05 (9)°. In the crystal, mol-ecules are arranged in a head-to-head manner, with the 3-nitro-phenyl groups nearly parallel to one another. The A and B mol-ecules are linked to one another via C-H⋯O hydrogen bonds, forming chains lying parallel to (-320) and enclosing R 2 (2)(10) and R 2 (2)(12) ring motifs. The meth-oxy group in both mol-ecules is positionally disordered with a refined occupancy ratio of 0.979 (4):0.021 (4) for mol-ecule A and 0.55 (4):0.45 (4) for mol-ecule B.

Crystal structure of (E)-1-(4'-methyl-[1,1'-biphen-yl]-4-yl)-3-(3-nitro-phen-yl)prop-2-en-1-one.

In the title compound, C22H17NO3, the mol-ecule has an E conformation about the C=C bond, and the C-C=C-C torsion angle is -177.7 (3)°. The planes of the terminal benzene rings are twisted by 41.62 (16)°, while the biphenyl unit is non-planar, the dihedral angle between the planes of the rings being 38.02 (15)°. The dihedral angle between the nitro-phenyl ring and the inner benzene ring is 5.29 (16)°. In the crystal, mol-ecules are linked by two weak C-H⋯π inter-actions, forming rectangular tubes propagating along the b-axis direction.

Methyl ({[(4E)-1,3-dimethyl-2,6-di-phenyl-piperidin-4-yl-idene]amino}-oxy)acetate.

In the title compound, C22H26N2O3, the piperidine ring exhibits a chair conformation. The phenyl rings attached to the piperidine at the 2- and 6-positions have axial orientations. These rings make a dihedral angle of 49.75 (11)°. The amino-oxy acetate group attached at the 4-position has an equatorial orientation. In the crystal, inversion dimers linked by pairs of C-H⋯π inter-actions occur.