The molecule of the title compound, C5H9NO3, is essentially planar [the maximum deviation for a non-H atom from the mean plane is 0.021 (3) Å] due to the π-conjugation of the hydroxyimino and carbonyl groups, which are trans to each other; ab initio calculations in vacuo at the DFT (B3LYP/6–311G**++) level of theory confirmed that E conformer is indeed the lowest in energy. The packing in crystal structure is influenced by strong intermolecular O—H⋯N hydrogen-bonding interactions between oxime groups and also by π-stacking of the molecules due to the carbonyl and oxime group orbital overlap [interplanar distance between adjacent molecules = 3.143 (4) Å]. Jointly, these factors afford infinite 6.32 Å thick molecular sheets, where the plane of each molecule is perpendicular to the plane of the sheet. Seen from above, the molecules within the sheet are arranged in a herringbone pattern. Such sheets form a stack due to weak van der Waals interactions; the gap between adjacent sheets is 2.07 Å.
The title centrosymmetric mononuclear complex, [Ni(C4H6NO3)2(H2O)2], is a polymorph of the previously reported complex [Dudarenko et al. (2010 ▶). Acta Cryst. E66, m277–m278]. The NiII atom, lying on an inversion center, is six-coordinated by two carboxylate O atoms and two oxime N atoms from two trans-disposed chelating 3-hydroxyiminobutanoate ligands and two axial water molecules in a distorted octahedral geometry. The hydroxy group forms an intramolecular hydrogen bond with the coordinated carboxylate O atom. The complex molecules are linked in stacks along  by a hydrogen bond between the water O atom and the carboxylate O atom of a neighboring molecule. The stacks are further linked by O—H⋯O hydrogen bonds into a layer parallel to (001).
The title compound, C14H16N6O2, is a second monoclinic polymorph of 2-[1-(3,5-dimethyl)pyrazolyl]-2-hydroxyimino-N′-[1-(2-pyridyl)ethylidene] acetohydrazide, with two crystallographically independent molecules per asymmetric unit. The non-planar molecules are chemically equal having similar geometric parameters. The previously reported polymorph [Plutenko et al. (2012 ▶). Acta Cryst. E68, o3281] was described in space group Cc (Z = 4). The oxime group and the O atom of the amide group are anti with respect to the C—C bond. In the crystal, molecules are connected by N—H⋯N hydrogen bonds into zigzag chains extending along the b axis.
The molecule of the title compound, C10H11N3O3, adopts an all-trans conformation and is approxomately planar, the largest deviation from the least-squares plane through all non-H atoms being 0.261 (1) Å. An intramolecular O—H⋯N hydrogen bond occurs. In the crystal, the molecules are packed into layers lying parallel to the ab plane by π-stacking interactions between the benzene ring of one molecule and the C—N bond of the oxime group of another molecule; the shortest intermolecular C⋯C separation within the layer is 3.412 (1) Å. The layers are connected by O—H⋯O and N—H⋯O hydrogen bonds.
The Ni atom of the title complex, [Ni(C8H8NO3)2]·2C3H7NO, lies on a center of inversion in a square-planar N2O2 coordination environment. An intramolecular O—H⋯O hydrogen bond exists between the oximic hydroxy group of one ligand and the metal-coordinated O atom of the symmetry-related ligand. The dimethylformamide solvent molecules are connected to the phenolate groups of the complex via O—H⋯O hydrogen bonds.
In the title compound, C9H10N4O2·H2O, the oxime unit has an E configuration, and an intramolecular N—H⋯N hydrogen bond results in the formation of a planar five-membered ring, which is oriented with respect to the aromatic ring at a dihedral angle of 74.82 (17)°. In the crystal structure, intermolecular O—H⋯O and N—H⋯O hydrogen bonds link the molecules and R
2(8) ring motifs are apparent.
In the title compound, C11H15N3O3S, the C—S—N(H)—N linkage is nonplanar, the torsion angle being 75.70 (12)°. The compound has two almost planar fragments linked to the S atom: the hydrazone-derivative fragment [(HONC4H6)N—N(H)–] and the tolyl fragment (C7H7–) have maximum deviations from the mean plane through the non-H atoms of 0.0260 (10) and 0.0148 (14) Å, respectively. The two planar fragments make an interplanar angle of 79.47 (5)°. In the crystal, molecules are connected through inversion centers via pairs of N—H⋯O and O—H⋯N hydrogen bonds.
In the title compound, C18H16ClNO4, the dihedral angle between the mean planes through the aromatic rings is 83.8 (8)°. The hydroxyethanimine group is essentially coplanar with the ring to which it is attached [O—N—C—C torsion angle = −177.96 (13)°]. The molecules are linked into centrosymmetric R
2(6) dimers via O—H⋯N hydrogen bonds. The crystal packing is further stabilized by C—H⋯O interactions.
In the title compound, C18H17NO4, the hydroxyethanimine group is essentially coplanar with the ring to which it is attached [C—C—N—O torsion angle = 179.94 (14)°]. The molecules are linked into cyclic centrosymmetric R
2(6) dimers via O—H⋯N hydrogen bonds and the crystal packing is further stabilized by C—H⋯O interactions.
In the title compound, [Cu(C6H9N2O2)2], the CuII atom is located on an inversion center and has a square-planar environment. Two 2-(hydroxyimino)cyclohexan-1-one oximate monoanions chelate to the CuII atom and the Cu—N distances are 1.920 (3) and 1.930 (3) Å. There are two short intramolecular O—H⋯O hydrogen bonds between the ligands. The complex molecules stack into columns extended along the c axis, with a Cu⋯Cu distance between adjacent molecules of 3.3060 (3) Å.
In the neutral, mononuclear title complex, [Ni(C4H6NO3)2(H2O)2], the Ni atom lies on a crystallographic inversion centre within a distorted octahedral N2O4 environment. Two trans-disposed anions of 3-hydroxyiminobutanoic acid occupy four equatorial sites, coordinated by the deprotonated carboxylate and protonated oxime groups and forming six-membered chelate rings, while the two axial positions are occupied by the water O atoms. The O atom of the oxime group forms an intramolecular hydrogen bond with the coordinated carboxylate O atom. The complex molecules are linked into chains along b by hydrogen bonds between the water O atom and the carboxylate O of a neighbouring molecule. The chains are linked by further hydrogen bonds into a layer structure.
The title compound, C12H15F2N2O+·C6H2N3O7
−, a picrate salt of 4-[(E)-(2,4-difluorophenyl)(hydroxyimino)methyl]piperidine, crystallizes with two independent molecules in a cation–anion pair in the asymmetric unit. In the cation, a methyl group is trisubstituted by hydroxyimino, piperidin-4-yl and 2,4-difluorophenyl groups, the latter of which contains an F atom disordered over two positions in the ring [occupancy ratio 0.631 (4):0.369 (4)]. The mean plane of the hydroxy group is in a synclinical conformation nearly orthogonal [N—C—C—C = 72.44 (19)°] to the mean plane of the piperidine ring, which adopts a slightly distorted chair conformation. The dihedral angle between the mean plane of the 2,4-difluorophenyl and piperidin-4-yl groups is 60.2 (3)°. In the picrate anion, the mean planes of the two o-NO2 and single p-NO2 groups adopt twist angles of 5.7 (2), 25.3 (7) and 8.3 (6)°, respectively, with the attached planar benzene ring. The dihedral angle between the mean planes of the benzene ring in the picrate anion and those in the hydroxyimino, piperidin-4-yl and 2,4-difluorophenyl groups in the cation are 84.9 (7), 78.9 (4) and 65.1 (1)°, respectively. Extensive hydrogen-bond interactions occur between the cation–anion pair, which help to establish the crystal packing in the unit cell. This includes dual three-center hydrogen bonds with the piperidin-4-yl group, the phenolate and o-NO2 O atoms of the picrate anion at different positions in the unit cell, which form separate N—H⋯(O,O) bifurcated intermolecular hydrogen-bond interactions. Also, the hydroxy group forms a separate hydrogen bond with a nearby piperidin-4-yl N atom, thus providing two groups of hydrogen bonds, which form an infinite two-dimensional network along (011).
The title compound, [ZnCl2(C10H12N4O2)]·0.5H2O, was readily prepared by the reaction between ZnCl2 and 2-hydroxyimino-N′-[1-(2-pyridyl)ethylidene]propanohydrazide. The Zn atom has a distorted trigonal–bipyramidal geometry with two Cl atoms and one azomethine N atom in the equatorial plane and one pyridine N atom and one amide O atom in the axial positions. In the crystal structure, complex molecules are connected in pairs by N—H⋯Cl hydrogen bonds, formed between the amide NH of one molecule and the Cl atom of a neighboring one. Molecular pairs are connected by hydrogen bonds involving the uncoordinated water molecule, which lies on a twofold axis.
The title compound, [Zn(C10H11N4O2)2]·2H2O, was prepared by the reaction between Zn(CH3COO)2·2H2O and 2-hydroxyimino-N′-[1-(2-pyridyl)ethylidene]propanohydrazide (Hpop). The central ZnII atom has a distorted tetragonal-bipyramidal coordination geometry formed by two amide O atoms and four N atoms of two azomethine and two pyridine groups. In the crystal, complex molecules form layers parallel to the crystallographic b direction. The layers are connected by O—H⋯N and O—H⋯O hydrogen bonds involving the solvent water molecules.
In the molecule of the title compound, C9H11N3O5S, the thiazole ring is oriented at dihedral angles of 87.33 (3) and 87.18 (3)° with respect to the planar (r.m.s. deviations 0.0136 and 0.0139 Å) methyl ester groups. The dihedral angle between the methyl ester groups is 44.20 (3)°. In the crystal structure, intermolecular N—H⋯N, N—H⋯O and C—H⋯O hydrogen bonds link the molecules along the a axis, through R
2(8) and R
2(22) ring motifs, forming infinite two-dimensional polymeric sheets. π–π Contacts between the thiazole rings [centroid–centroid distance = 3.536 (2) Å] may further stabilize the structure.
In the title compound, C9H10N4O2, the pyridine ring is twisted by 16.5 (1)° from the mean plane defined by the remaining non-H atoms. An intramolecular N—H⋯N interaction is present. In the crystal, intermolecular O—H⋯N and N—H⋯O hydrogen bonds link molecules into layers parallel to the bc plane. The crystal packing exhibits π–π interactions indicated by the short distance of 3.649 (1) Å between the centroids of the pyridine rings of neighbouring molecules.
In the title compound, C15H13N3O3, the dihedral angle formed by the two benzene rings is 44.23 (2)°. The crystal structure is stabilized by aromatic π–π stacking interactions, with centroid-centroid distances of 3.825 (3) and 3.870 (4) Å between the aniline and the nitrobenzene rings of neighbouring molecules, respectively. In addition, the stacked molecules exhibit intermolecular C—H⋯N and C—H⋯O interactions.
In the title compound, C20H21NO4, the two benzene rings are almost perpendicular to each other, making a dihedral angle of 86.1 (7)°. The hydroxyethanimine group is essentially coplanar with the benzene ring, the largest deviation from the mean plane of the hydroxyethanimine [C=N—OH] group being 0.011 (1) Å for the O atom. An intramolecular C—H⋯O hydrogen bond occurs. The molecules are linked into cyclic centrosymmetric R
2(6) dimers via O—H⋯N hydrogen bonds. Intermolecular C—H⋯O hydrogen bonds link the molecules, forming a C(8) chain along the a axis. The crystal packing is further stabilized by C—H⋯π interactions.
In the title compound, C8H6N2O3, the indol-2-one system is almost planar [maximum deviation = 0.010 (3) Å]. In the crystal structure, intermolecular N—H⋯O, O—H⋯N and O—H⋯O hydrogen bonds link the molecules into a three-dimensional network. π–π contacts between the indole ring systems [centroid–centroid distances = 3.494 (1), 3.731 (1) and 3.736 (1) Å] may further stabilize the structure.
In the title compound, C18H16N2O2, the hydroxyethanimine group is essentially coplanar with the ring to which it is attached (C—C—N—O torsion angle = −176.9°). Molecules are linked into cyclic centrosymmetric R
2(6) dimers via O—H⋯N hydrogen bonds.
In the title compound, C20H21NO5, the dihedral angle between the mean planes through the two rings is 47.1 (8)°. The enoate group assumes an extended conformation. The hydroxyethanimine group is essentially coplanar with the benzene ring, the largest deviation from the mean plane being 0.061 (1) Å for the O atom. In the crystal, molecules are linked into cyclic centrosymmetric dimers with an R
2(6) motif via pairs of O—H⋯N hydrogen bonds. Intermolecular C—H⋯O hydrogen bonds form a C(8) chain along the b axis. The crystal packing is further stabilized by C—H⋯π interactions.
In the title compound, C19H19NO4, the dihedral angle between the mean planes through the benzene rings is 82.18 (7)°. The C=N double bond is trans-configured. The molecules are linked into centrosymmetric dimers via pairs of O—H⋯N hydrogen bonds with the motif R
2(6). The crystal packing also features C—H⋯O interactions. The methyl group attached to one of the aromatic rings is disordered over two almost equally occupied positions [occpancy ratio = 0.51 (4):0.49 (4)].
The title compound, C10H12N4O2, features an intramolecular N—H⋯N hydrogen bond formed between the imine NH and oxime N atoms. The oxime group and the amide C=O bond are anti to each other. In the crystal, molecules are connected by O—H⋯O hydrogen bonds into supramolecular zigzag chains along the c axis.
The title compound, C15H13ClN2O2, adopts an E conformation with respect to the azomethine C=N bond. The aniline and phenol rings are almost coplanar, making a dihedral angle of 3.33 (2)°. In the crystal, the molecules lie about inversion centers, forming dimers that are connected by intermolecular O—H⋯N hydrogen bonds, resulting in six-membered rings with graph-set motif R
2(6). In addition, there is a strong intermolecular O—H⋯N hydrogen-bonding interaction, resulting in an S(6) ring motif. Weak π–π interactions between the benzene rings [centroid–centroid distance = 3.809 (1) Å] further stabilize the crystal structure.
In the title compound, C14H11BrN2O2, the mean planes of the two benzene rings are almost parallel to each other, making a dihedral angle of 4.09 (1)°. An intramolecular O—H⋯N hydrogen bond occurs. In the crystal, intermolecular O—H⋯N and C—H⋯O hydrogen bonds link the molecules into a chain-like supramolecular structure.