(E)-2-[(2-Hydr­oxy-5-nitro­phen­yl)iminiometh­yl]-4-nitro­phenolate

The title mol­ecule, C13H9N3O6, consists of a 2-hydr­oxy-5-nitro­phenyl­iminio group and a 4-nitro­phenolate group bonded to a methyl­ene C atom with both of the planar six-membered rings nearly in the plane of the mol­ecule [dihedral angle = 1.3 (4)°]. Each of the nitro O atoms is twisted slightly out of the plane of the mol­ecule. The amine group forms an intra­molecular hydrogen bond with both nearby O atoms, each of which has partial occupancy of attached H atoms [0.36 (3) and 0.64 (3)]. An extended π-delocalization throughout the entire mol­ecule exists producing a zwitterionic effect in this region of the mol­ecule. The shortened phenolate C—O bond [1.2749 (19)°], in concert with the slightly longer phenol C—O bond [1.3316 (19) Å], provides evidence for this effect. The crystal packing is influenced by extensive strong inter­molecular O—H⋯O hydrogen bonding between the depicted phenolate and hydr­oxy O atoms and their respective H atoms within the π-delocalized region of the mol­ecule. As a result, mol­ecules are linked into an infinite polymeric chain diagonally along the [110] plane of the unit cell in an alternate inverted pattern. A MOPAC AM1 calculation provides support for these observations

(E)-2-[(2-Hydr­oxy-5-nitro­phen­yl)iminiometh­yl]phenolate

In the title mol­ecule, C13H10N2O4, the dihedral angle between the mean planes of the benzene and phenolate rings is 21.6 (4)°. The nitro O atoms are twisted slightly out of the plane of the ring to which the nitro group is attached [dihedral angle 8.4 (3)°]. The amine group forms an intra­molecular hydrogen bond with both nearby O atoms. An extended π delocalization throughout the entire mol­ecule exists producing a zwitterionic effect in this region of the mol­ecule. The shortened C—O bond [1.2997 (15) Å] in concert with the slightly longer C—OH bond [1.3310 (16) Å] provide evidence for this effect. The crystal packing is influenced by strong inter­molecular O—H⋯O hydrogen bonding. As a result, mol­ecules are linked into an infinite zigzag chain running along the b axis. A MOPAC PM3 calculation provides support to these observations

(2E)-3-{4-[(1H-1,3-Benzimidazol-2-yl)meth­oxy]-3-eth­oxy­phen­yl}-1-(4-bromo­phen­yl)prop-2-en-1-one monohydrate

In the title compound, C25H21BrN2O3·H2O, the benzimidazole fragment and the water mol­ecule of crystallization are each disordered over two sets of sites of equal occupancy. The dihedral angles between the least-squares planes of the benzimidazole and the 3-eth­oxy- and 4-bromo­benzene rings are 86.9 (6) and 85.1 (1)°, respectively in one disorder component. The crystal packing is stabilized by inter­molecular O—H⋯O, O—H⋯N and N—H⋯N hydrogen bonds, which link the mol­ecules into chains along the a axis

3-[(Z)-(4-Diethyl­amino-6-oxocyclo­hexa-2,4-dien-1-yl­idene)methyl­amino]benzoic acid

The title compound, C18H20N2O3, crystallizes as the keto tautomer, unlike the vast majority of similar structures that have been reported that contain the hydr­oxy tautomer. There are two strong hydrogen bonds in the crystal structure, both accepted by the same carbonyl group: one intra­molecular N—H⋯O and one inter­molecular O—H⋯O. As a result, the carbonyl C=O distance is long, at 1.310 (2) Å, which may suggest the mol­ecule has a significant zwitterionic character. The dihedral angle between the benzene ring planes is 15.05 (7)°. As a result of the intramolecular hydrogen bond, the bridging C—C=N—C group is almost coplanar with the benzene ring that has the diethylamino substituent [dihedral angle 2.35 (15)°]

(1R,3S)-1,1′-(1,3-Dihydro-2-benzofuran-1,3-diyl)bis(1,3-dimethyl­urea)

In the mol­ecule of the title compound, C14H20N4O3, the five-membered ring adopts an envelope conformation with the O atom displaced by 0.207 (3) Å from the plane of the other ring atoms. Intra­molecular C—H⋯O hydrogen bonds result in the formation of three five-membered rings having envelope conformations. In the crystal structure, inter­molecular N—H⋯O hydrogen bonds link the mol­ecules, forming R 2 2(20) ring motifs, which produce two-dimensional polymeric sheets extending along the b axis. There are also two C—H⋯π inter­actions. The H atoms of one of the methyl groups are disordered over two positions and were refined with occupancies of 0.50

Bis(2,6-diamino­pyridinium) bis­(hydrogen oxalate) monohydrate

The asymmetric unit of the title compound, 2C5H8N3 +·2C2HO4 −·H2O, contains two crystallographically independent 2,6-diamino­pyridinium cations, a pair of hydrogen oxalate anions and a water mol­ecule. Both 2,6-diamino­pyridinium cations are planar, with maximum deviations of 0.011 (2) and 0.015 (1) Å, and are protonated at the pyridine N atoms. The hydrogen oxalate anions adopt twisted conformations and the dihedral angles between the planes of their carboxyl groups are 31.01 (11) and 63.48 (11)°. In the crystal, the cations, anions and water mol­ecules are linked via O—H⋯O and N—H⋯O hydrogen bonds, forming a three-dimensional network

Synthesis, spectroscopic characterizations and quantum chemical computational studies of (Z)-4-[(E)-p-tolyldiazenyl]-6-[(2-hydroxyphenylamino)methylene]-2-methoxycyclohexa-2,4-dienone.

In this study, the molecular structure and spectroscopic properties of title compound were characterized by X-ray diffraction, FT-IR and UV-vis spectroscopies. These properties of title compound were also investigated from calculative point of view. The X-ray diffraction and FT-IR analyses reveal the existence of keto form in the solid state. 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 exists in enol form in benzene. In addition, the title compound in DMSO showed new absorption band at 436 nm due to the high ionizing effect of this solvent. The geometry optimization of title compound in gas phase was performed using DFT method with B3LYP applying 6-311G(d,p) basis set. TD-DFT calculations starting from optimized geometry were carried out in gas phase to calculate excitation energies of title compound. The non-linear optical properties were computed with the same level of theory and title compound showed a good second order nonlinear optical property. In addition, thermodynamic properties were obtained in the range of 100-500 K

Existence of a resonance hybrid structure as a result of proton tautomerism in (±)-(E)-4-bromo-2-[(2,3-dihydroxypropylimino) methyl]phenol racemate.

o-Hydroxy Schiff bases have two tautomers known as phenol-imine and keto-amine forms. In the present work, the tautomerism in (E)-4-Bromo-2-[(2,3-dihydroxypropylimino)methyl]phenol compound has been investigated by experimental (XRD, FT-IR and UV-vis) and computational (DFT and TD-DFT) methods. The X-ray diffraction (XRD) study reveals that the title compound favors a resonance hybrid structure of phenol-imine and keto-amine forms in the solid state rather than having these forms separately or jointly. Experimental UV-vis study of proton transfer process in solvent media (Benzene, DMSO and EtOH) shows the preference of phenol-imine form in benzene while both phenol-imine and keto-amine characteristics are present in EtOH and DMSO

(1Z)-Phthalazin-1(2H)-one iso­propyl­­idene­hydrazone

The crystal structure of the title compound, C11H12N4, is stabilized by an N—H⋯N and three C—H⋯N inter­molecular hydrogen bonds. The N—H⋯N hydrogen bonds generate centrosymmetric R22(6) rings, while the three C—H⋯N hydrogen bonds forms edge-fused R22(7)R22(7)R22(10) ring motifs. Except for four H atoms of the methyl groups, all atoms are in the same plane and the dihedral angles between the aromatic and heterocyclic rings and the substituent group plane are 1.87 (5) and 1.53 (5)°, respectively