Synthesis, spectroscopic characterizations and quantum chemical computational studies of (Z)-4-[(E)-(4-fluorophenyl)diazenyl]-6-[(3-hydroxypropylamino)methylene]-2-methoxycyclohexa-2,4-dienone.

In this study, the molecular structure and spectroscopic properties of the title compound were characterized by X-ray diffraction, FT-IR and UV-vis spectroscopies. These properties were also investigated using DFT method. The most convenient conformation of title compound was firstly determined. The geometry optimizations in gas phase and solvent media were performed by DFT methods with B3LYP adding 6-31G(d) basis set. The differences between crystal and computational structures are due to crystal packing in which hydrogen bonds play an important role. UV-vis spectra were recorded in different organic solvents. The results show that title compound exists in both keto and enol forms in DMSO, EtOH but it tends to shift towards enol form in benzene. The polar solvents facilitate the proton transfer by decreasing the activation energy needed for Transition State. The formation of both keto and enol forms in DMSO and EtOH is due to decrease in the activation energy. TD-DFT calculations starting from optimized geometry were carried out in both gas and solution phases to calculate excitation energies of the title compound. The non-linear optical properties were computed at the theory level and the title compound showed a good second order non-linear optical property. In addition, thermodynamic properties were obtained in the range of 100-500K.

(E)-5-Meth-oxy-2-(o-tolyl-imino-meth-yl)phenol.

In the title compound, C(15)H(15)NO(2), the phenol group make dihedral angles of 2.4 (2) and 24.1 (9)° with the imine linkage (-C=N-) and the phenyl group, respectively, and the mol-ecule adopts the enol-imine tautomeric form, so the mol-ecular structure is stabilized by a strong intra-molecular O-H⋯N hydrogen bond. The crystal structure features a weak C-H⋯π inter-action.

(E)-2-[(4-Fluoro-phen-yl)imino-meth-yl]-5-methoxy-phenol.

In the mol-ecule of the title compound, C(14)H(12)FNO(2), the aromatic rings are oriented at a dihedral angle of 48.17 (1)°. An intra-molecular O-H⋯N hydrogen bond results in the formation of a six-membered ring. The title mol-ecule is a phenol-imine tautomer, as evidenced by the C-O [1.351 (3) Å], C-N [1.282 (3) Å], and C-C [1.416 (3)-1.445 (3) Å] bond lengths. In the crystal, mol-ecules are linked by inter-molecular C-H⋯π inter-actions.

(E)-4-Meth-oxy-2-(p-tolyl-imino-meth-yl)phenol.

The mol-ecule of the title compound, C(15)H(15)NO(2), adopts the enol-imine tautomeric form and has a strong intra-molecular O-H⋯N hydrogen bond as a result. The mol-ecule is almost planar, with a maximum deviation of 0.1038 (15) Šfor the meth-oxy C atom. A weak C-H⋯π inter-action and a weak C-H⋯O hydrogen bond are present in the crystal.

(E)-2-Eth-oxy-6-[(4-ethoxy-phen-yl)imino-meth-yl]phenol.

In the asymmetric unit of the title compound, C(17)H(19)NO(3), there are three independent mol-ecules, which are align nearly parallel to each other and adopt the phenol-imine tautomeric form. In each mol-ecule, an intra-molecular O-H⋯N hydrogen bond results in the formation of an S(6) ring motif. The dihedral angles between the aromatic rings in the three independent mol-ecules are 13.55 (2), 21.24 (2) and 46.26 (1)°. C-H⋯π inter-actions are also observed in the crystal structure.

(Z)-6-[(5-Chloro-2-hydroxy-phenyl)-aminomethyl-ene]-2-ethoxy-cyclo-hexa-2,4-dienone.

The title compound, C(15)H(14)ClNO(3), exists as the keto-amine form in the crystal and two intra-molecular N-H⋯O hydrogen bonds are observed. The aromatic rings are oriented at a dihedral angle of 5.85 (8)°. In the crystal structure, inter-molecular O-H⋯O and C-H⋯O hydrogen bonds link the mol-ecules into chains. A π-π contact between the benzene rings [centroid-centroid distance = 3.6623 (10) Å] further stabilizes the structure.

(E)-2-[(4-Ethoxy-phen-yl)imino-meth-yl]-4-methoxy-phenol.

In the mol-ecule of the title compound, C(16)H(17)NO(3), the aromatic rings are oriented at a dihedral angle of 29.25 (8)°. An intra-molecular O-H⋯N hydrogen bond results in the formation of a nearly planar [maximum deviation 0.034 (13) Å] six-membered ring, which is oriented at dihedral angles of 0.91 (1) and 28.91 (12)° with respect to the aromatic rings. The title mol-ecule is a phenol-imine tautomer, as evidenced by C-O, C-N and C-C bond lengths. In the crystal, mol-ecules are linked by inter-molecular C-H⋯O hydrogen bonds that generate C(8) chains.

(E)-4-Meth-oxy-2-(o-tolyl-imino-meth-yl)phenol.

In the mol-ecule of the title compound, C(15)H(15)NO(2), the aromatic rings are oriented at a dihedral angle of 15.46 (6)°. An intra-molecular O-H⋯N hydrogen bond results in the formation of a nearly planar six-membered ring [maximum deviation of 0.035 (5) Šfor the N atom] which is almost coplanar with the adjacent ring, making a dihedral angle of 0.8 (3)°. The title organic mol-ecule is a phenol-imine tautomer, as evidenced by the C-O, C-N and C-C bond lengths. Mol-ecules are linked by inter-molecular C-H⋯O hydrogen bonds that generate a C(5) chain. C-H⋯π and π-π inter-actions exist in the structure. The π-π inter-action occurs between the phenol ring and its symmetry equivalent at (1 - x, 1 - y, -z), with a centroid-centroid distance of 3.727 (7) Šand a plane-to-plane separation of 3.383 (5) Å, resulting in an offset angle of 24.82 (1)°.

(Z)-6-[(5-Chloro-2-hydroxy-anilino)-methyl-ene]-4-methoxy-cyclo-hexa-2,4-dienone 0.25-hydrate.

The title compound, C(14)H(12)ClNO(3)·0.25H(2)O, exists in the keto-amine form, and the aromatic rings are oriented at a dihedral angle of 7.24 (7)°. Bifurcated intra-molecular N-H⋯(O,O) hydrogen bonds result in the formation of planar six- and five-membered rings. In the crystal structure, inter-molecular O-H⋯O and C-H⋯O hydrogen bonds link the mol-ecules into chains. π-π contacts between benzene rings [centroid-centroid distance = 3.5065 (9) Å] may further stabilize the structure. There also exists a weak C-H⋯π inter-action.

1,4-Bis[2-(1,3-benzothia-zol-2-yl)phen-oxy]butane.

The mol-ecule of the title compound, C(30)H(24)N(2)O(2)S(2), adopts a transoid conformation consistent with the inversion centre located at the mid-point of the central C-C single bond, resulting in one half mol-ecule in the asymmetric unit. The dihedral angle between the coplanar benzothia-zole ring system and the benzene ring is 11.06 (7)°. In the crystal structure, mol-ecules are linked by weak inter-molecular π-π inter-actions between thia-zole and benzene rings to form a three-dimensional network.

X-ray crystal and computational structural study of (E)-2-[(2-chloro-phenyl)-iminometh-yl]-4-methoxy-phenol.

In the mol-ecule of the title compound, C(14)H(12)ClNO, the two aromatic rings are oriented at a dihedral angle of 12.28 (7)°. An intra-molecular O-H⋯N hydrogen bond results in the formation of a nearly planar six-membered ring, which is oriented with respect to the aromatic rings at dihedral angles of 0.18 (5) and 12.10 (6)°. In the crystal structure, weak inter-molecular C-H⋯O hydrogen bonds link the mol-ecules into chains along the c axis. There is a C-H⋯π contact between the methyl group and the chloro-phenyl ring and a π-π contact between the two benzene rings [centroid-centroid distance = 3.866 (1) Å].

X-ray and computational structural study of (E)-2-(4-chloro-phenyl-imino-meth-yl)-4-methoxy-phenol.

In the mol-ecule of the title compound, C(14)H(12)ClNO(2), the two aromatic rings are oriented at a dihedral angle of 5.92 (7)°. An intra-molecular O-H⋯N hydrogen bond results in the formation of a nearly planar six-membered ring, which is oriented at dihedral angles of 1.55 (4) and 5.95 (4)° with respect to the phenol and chlorophenyl rings, respectively. In the crystal structure, weak inter-molecular C-H⋯O hydrogen bonds link the mol-ecules into a three-dimensional network.

Three (E)-2-[(bromophenyl)iminomethyl]-4-methoxyphenols.

The title compounds, (E)-2-[(2-bromophenyl)iminomethyl]-4-methoxyphenol, C(14)H(12)BrNO(2), (I), (E)-2-[(3-bromophenyl)iminomethyl]-4-methoxyphenol, C(14)H(12)BrNO(2), (II), and (E)-2-[(4-bromophenyl)iminomethyl]-4-methoxyphenol, C(14)H(12)BrNO(2), (III), adopt the phenol-imine tautomeric form. In all three structures, there are strong intramolecular O-H...N hydrogen bonds. Compound (I) has strong intermolecular hydrogen bonds, while compound (III) has weak intermolecular hydrogen bonds. In addition to these intermolecular interactions, C-H...pi interactions in (I) and (III), and pi-pi interactions in (I), play roles in the crystal packing. The dihedral angles between the aromatic rings are 15.34 (12), 6.1 (3) and 39.2 (14) degrees for (I), (II) and (III), respectively.