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1.  2,2′-[Imidazolidine-1,3-diylbis(methyl­ene)]diphenol 
In the title mol­ecule, C17H20N2O2, the imidazolidine ring adopts a twist conformation. The mean plane through the five atoms of the imidazolidine ring makes dihedral angles of 70.18 (4) and 74.14 (4)° with the planes of the two aromatic rings. The dihedral angle between the benzene rings is 53.11 (5)°. Both phenol –OH groups form intra­molecular hydrogen bonds to the N atoms, with graph-set motif S(6). In the crystal, pairs of O—H⋯O hydrogen bonds link the mol­ecules into dimers with R 4 4(18) ring motifs. The crystal packing is further stabilized by C—H⋯O and weak C—H⋯π inter­actions.
doi:10.1107/S1600536811053748
PMCID: PMC3254510  PMID: 22259455
2.  6,6′-Dimethyl-2,2′-[imidazolidine-1,3-diyl­bis(methyl­ene)]diphenol 
In the title compound, C19H24N2O2, a di-Mannich base derived from 2-methyl­phenol and 1,3,6,8-tetra­aza­tri­cyclo­[4.4.1.13,8]dodecane, the imidazolidine ring adopts a twist conformation, with a twist about the ring N—C bond [C—N—C—C torsion angle = −44.34 (14)°]. The two 2-hy­droxy-3-methyl­benzyl groups are located in trans positions with respect to the imidazolidine fragment. The structure displays two intra­molecular O—H⋯N hydrogen bonds, which each form an S(6) ring motif. In the crystal, the mol­ecules are linked by weak C—H⋯O inter­actions with a bifurcated acceptor, forming a three-dimensional network.
doi:10.1107/S1600536814002128
PMCID: PMC3998388  PMID: 24764964
3.  4,4′-Dimethyl-2,2′-[imidazolidine-1,3-diylbis(methyl­ene)]diphenol 
The imidazolidine ring in the title compound, C19H24N2O2, adopts a twist conformation and its mean plane (r.m.s. deviation = 0.19 Å) makes dihedral angles of 72.38 (9) and 71.64 (9)° with the two pendant aromatic rings. The dihedral angle between the phenyl rings is 55.94 (8)°. The mol­ecular structure shows the presence of two intra­molecular O—H⋯N hydrogen bonds between the phenolic hydroxyl groups and N atoms with graph-set motif S(6). In the crystal, C—H⋯O hydrogen bonds lead to the formation of chains along the b-axis direction.
doi:10.1107/S1600536812042808
PMCID: PMC3515265  PMID: 23284485
4.  6,6′-Dimeth­oxy-2,2′-[2,2-dimethyl­propane-1,3-diylbis(nitrilo­methyl­idyne)]diphenol 
The title Schiff base compound, C21H26N2O4, exhibits two crystallographically independent mol­ecules in the asymmetric unit with similar conformations. The imino groups are coplanar with the benzene rings; the maximum deviations of the N atoms from the planes comprising the benzene rings and the imino groups are −0.037 (4), 0.013 (4), −0.021 (5), and 0.008 (5) Å. The dihedral angles between the benzene rings in the two mol­ecules are 53.64 (17) and 51.93 (17)°. Strong intra­molecular O—H⋯N hydrogen bonds generate S(6) ring motifs. The N atoms are also in close proximity to the H atoms of the dimethyl­propane groups, with H⋯N distances between 2.54 and 2.75 Å. The crystal structure is further stabilized by weak inter­molecular C—H⋯O hydrogen bonds, weak inter­molecular C—H⋯π inter­actions and π–π contacts involving the imine C atom and two C atoms from the adjacent benzene rings.
doi:10.1107/S1600536808038002
PMCID: PMC2967940  PMID: 21581654
5.  2,2′-[1,3-Diazinane-1,3-diylbis(methyl­ene)]bis­(4-bromo­phenol) 
The title compound, C18H20Br2N2O2, the heterocyclic ring adopts a chair conformation. The benzene rings make dihedral angles of 86.84 (10) and 60.73 (10)° with the mean plane of the heterocyclic ring. The dihedral angle between the two benzene rings is 79.77 (10)°. The mol­ecular structure is stabilized by two intra­molecular hydrogen bonds between the phenolic hy­droxy groups and N atoms with graph-set motif S(6). The crystal structure is stabilized by weak C—H⋯π inter­actions.
doi:10.1107/S1600536812001985
PMCID: PMC3275243  PMID: 22347099
6.  4,4′-Dichloro-2,2′-[imidazolidine-1,3-diylbis(methylene)]diphenol 
The imidazolidine ring in the title compound, C17H18Cl2N2O2, adopts a twist conformation. The observed conformation is stabilized by two intra­molecular O—H⋯N hydrogen bonds, with both N atoms acting as hydrogen-bond acceptors. The phenyl substituents are aligned at 70.0 (1) and 76.6 (1)° with respect to the best plane through the five atoms of the imidazolidine ring. Weak inter­molecular C—H⋯O inter­actions stabilize the crystal packing.
doi:10.1107/S1600536811035677
PMCID: PMC3201546  PMID: 22065817
7.  5,5′-Dimeth­oxy-2,2′-[2,2-dimethyl­propane-1,3-diylbis(nitrilo­methyl­idyne)]diphenol 
The asymmetric unit of the title Schiff base compound, C21H26N2O4, consists of four crystallographically independent mol­ecules, viz. A, B, C and D. The A and D, and the B and C mol­ecules are related by a pseudo-inversion centre, and the remaining pairs of mol­ecules differ in the orientations of one of the meth­oxy groups. In each independent mol­ecule, intra­molecular O—H⋯N hydrogen bonds generate two S(6) ring motifs. The dihedral angles between the benzene rings in mol­ecules A, B, C and D are 65.86 (19), 50.41 (19), 68.59 (19) and 50.85 (19)°, respectively. In the crystal structure, mol­ecules are linked by C—H⋯O hydrogen bonds, forming R 2 2(8) dimers. In addition, weak C—H⋯π inter­actions are observed.
doi:10.1107/S1600536808037690
PMCID: PMC2959808  PMID: 21581360
8.  Dimethyl 4,4′-dihy­droxy-3,3′-{[(3aRS,7aRS)-2,3,3a,4,5,6,7,7a-octa­hydro-1H-1,3-benzimidazole-1,3-di­yl]bis­(methyl­ene)}dibenzoate 
The title compound, C25H30N2O6, has the imidazolidine ring in an envelope conformation. There are two intra­molecular O—H⋯N hydrogen-bond inter­actions with graph-set motif S(6). The cyclo­hexane ring adopts a slightly distorted chair conformation. One methyl carboxyl­ate substituent forms a dihedral angle of 12.00 (5)° with the plane of the benzene ring, while the other methyl carboxyl­ate group is almost coplanar, making a dihedral angle of 2.26 (9)°. In the crystal, pairs of inter­molecular C—H⋯O hydrogen bonds form racemic dimers, corresponding to an R 2 2(18) graph-set motif. Further weak C—H⋯O inter­actions generate a chain running along the c axis.
doi:10.1107/S1600536811040906
PMCID: PMC3247326  PMID: 22219944
9.  4,4′-[Thio­phene-2,5-diylbis(ethyne-2,1-di­yl)]dibenzonitrile 
In the solid state, the title compound, C22H10N2S, forms centrosymmetric dimers by pairs of non-classical C—H⋯S hydrogen bonds linking approximately coplanar mol­ecules. The benzene ring involved in this inter­action makes a dihedral angle of only 7.21 (16)° with the thio­phene ring, while the other benzene ring is twisted somewhat out of the plane, with a dihedral angle of 39.58 (9)°. The hydrogen-bonded dimers stack on top of each other with an inter­planar spacing of 3.44 Å. C—H⋯N hydrogen bonds link together stacks that run in approximately perpendicular directions. Each mol­ecule thus inter­acts with 12 adjacent mol­ecules, five of them approaching closer than the sum of the van der Waals radii for the relevant atoms. Optimization of the inter-stack contacts contributes to the non-planarity of the mol­ecule.
doi:10.1107/S1600536808008106
PMCID: PMC2961030  PMID: 21202153
10.  A second tricilinc polymorph of 6,6′-dieth­oxy-2,2′-[propane-1,2-diylbis(nitrilo­methyl­idyne)]diphenol 
The title Schiff base compound, C21H26N2O4, is a second triclinic polymorph of a previously reported room-temperature structure [Jia (2009 ▶). Acta Cryst. E65, o646]. Strong intra­molecular O—H⋯N hydrogen bonds generate S(6) ring motifs. Inter­molecular C—H⋯O inter­actions link neighbouring mol­ecules into dimers with an R 2 2(16) ring motif. The mean planes of the two benzene rings are almost perpendicular to each other, making a dihedral angle of 88.24 (5)°. An inter­esting feature of the crystal structure is the intermolecular short C⋯O [3.1878 (13) Å] contact which is shorter than the sum of the van der Waals radii of the relevant atoms. The crystal structure is further stabilized by inter­molecular C—H⋯π and π–π inter­actions [centroid–centroid distance = 3.7414 (6) Å]. The structure has a stereogenic centre but the space group is centrosymmetric, so the mol­ecule exists as a racemate.
doi:10.1107/S1600536809008137
PMCID: PMC2968989  PMID: 21582458
11.  3,3′-[Biphenyl-4,4′-diylbis(­oxy)]diphthalic acid 
In the title mol­ecule, C28H18O10, the two central benzene rings form a dihedral angle of 31.0 (1)°. In the phthalic acid fragments, the carb­oxy groups in the meta positions are approximately coplanar with the attached benzene rings, being inclined to their planes at 2.7 (1) and 10.3 (1)°, while the carb­oxy groups in the ortho positions are twisted from the benzene ring planes by 83.5 (1) and 75.4 (1)°. In the crystal, O—H⋯O hydrogen bonds link the mol­ecules into layers parallel to the bc plane. Weak C—H⋯O hydrogen bonds and π–π inter­actions between the aromatic rings [centroid–centroid distance = 3.7674 (3) Å] further consolidate the crystal packing.
doi:10.1107/S1600536811053219
PMCID: PMC3254545  PMID: 22259493
12.  6,6′-Diethoxy-2,2′-[2,2-dimethylpropane-1,3-diylbis(nitrilomethylidyne)]diphenol 
In the crystal structure, the title Schiff base compound, C23H30N2O4, exhibits crystallographic twofold rotation symmetry. The imino group is coplanar with the aromatic ring with an N—C—C—C torsion angle of -179.72 (9)°. An intra­molecular O—H⋯N hydrogen bond forms a six-membered ring, producing an S(6) ring motif. The dihedral angle between symmetry related benzene rings is 28.05 (5)°. The eth­oxy group makes a C—O—C—C torsion angle of −7.20 (16)° with the benzene ring. The crystal structure is stabilized by inter­molecular C—H⋯π inter­actions.
doi:10.1107/S1600536809007557
PMCID: PMC2969095  PMID: 21582445
13.  3,3′-Dibenzyl-1,1′-[naphthalene-1,4-diylbis(methyl­ene)]di(1H-imidazol-3-ium) bis­(hexa­fluoro­phosphate) 
In the title N-heterocyclic carbene compound, C32H30N4 2+·2PF6 −, the mean plane of the naphthalene ring system makes dihedral angles of 79.15 (15) and 76.85 (16) with the imidazole rings and 56.15 (19) and 80.56 (16)° with the benzene rings. An intra­molecular C—H⋯N hydrogen bond occurs. The crystal structure is stabilized by C—H⋯F inter­actions. In addition, π–π inter­actions [centroid–centroid distances = 3.848 (1) and 3.574 (3) Å] are observed. The nine equatorial F atoms in the two PF6 − anions were disordered over two positions with occupancy ratios of 0.545 (10):0.455 (10) and 0.793 (11):0.207 (11) in the two anions.
doi:10.1107/S1600536811032132
PMCID: PMC3200774  PMID: 22064506
14.  Enrofloxacinium picrate 
There is one cation–anion pair in the asymmetric unit of the title compound [systematic name: 4-(3-carb­oxy-6-fluoro-4-oxo-1,4-dihydroquinolin-7-yl)-1-ethyl­piperazin-1-ium 2,4,6-tri­nitro­phenolate], C19H23FN3O3 +·C6H2N3O7 −. The six-membered piperazine group in the cation adopts a slightly distorted chair conformation and contains a protonated N atom. The dihedral angles between the mean planes of the cyclo­propyl and piperazine rings in the cation with the 10-atom ring system of the quinolone group are 48.1 (1) and 69.9 (5)°, respectively. The picrate anion inter­acts with the protonated N atom of an adjacent cation through a bifurcated N—H⋯O three-center hydrogen bond, forming an R 1 2(6) ring motif. Furthermore, there is an intra­molecular O—H⋯O hydrogen bond. The dihedral angle between the mean planes of the anion benzene and cation piperizine, quinoline and cyclo­propyl rings are 61.3 (6), 31.1 (4) and 70.4 (9)°, respectively. The mean planes of the two o-NO2 and single p-NO2 groups in the picrate anion are twisted by 6.7 (6), 38.3 (9) and 12.8 (7)° with respect to the mean plane of the benzene ring. Strong N—H⋯O and weak inter­molecular C—H⋯O hydrogen bonds in concert with weak π–π stacking inter­actions [centroid–centroid distances = 3.5785 (13), 3.7451 (12) and 3.6587 (13) Å] dominate the crystal packing.
doi:10.1107/S160053681100170X
PMCID: PMC3051675  PMID: 21523099
15.  4,4′-Di-tert-butyl-2,2′-[imidazolidine-1,3-diylbis(methyl­ene)]diphenol 
In the title compound, C25H36N2O2, the two tert-butyl-substituted benzene rings are inclined at an angle of 53.5 (3)° to one another. The imidazolidine ring has an envelope conformation with with one of the C atoms of the ethylene fragment as the flap. The structure displays two intra­molecular O—H⋯N hydrogen bonds that generate S(6) ring motifs. The crystal studied was a non-merohedral twin with a fractional contribution of 0.281(6) for the minor domain.
doi:10.1107/S1600536813017157
PMCID: PMC3770425  PMID: 24046710
16.  2,2′-{1,1′-[Pentane-1,5-diyl­bis(oxy­nitrilo)]­diethyl­idyne}diphenol 
In the title compound, C21H26N2O4, there is half a mol­ecule in the asymmetric unit with a crystallographic twofold rotation axis passing through the central C atom of the –CH=N—O—(CH2)5—O—N=CH– bridge. The dihedral angle formed by the two benzene rings is 80.85 (2)°. Strong intra­molecular O—H⋯N and C—H⋯O hydrogen bonds help to establish the molecular conformation. There are also weak inter­molecular π–π stacking inter­actions between neighbouring benzene rings [centroid–centroid separation = 3.502 (3) Å].
doi:10.1107/S160053680803136X
PMCID: PMC2959680  PMID: 21580925
17.  (6′R*,7′R*)-7′-(1,3,-Diphenyl-1H-pyrazol-4-yl)-1,2,5′,6′,7′,7a’,3′′,4′′-octa­hydro-1′H,2′′H-dispiro­[acenaphthyl­ene-1,5′-pyrrolo­[1,2-c][1,3]thia­zole-6′,3′′-[1]benzopyran]-2,4′′-dione 
In the title compound, C40H29N3O3S, the pyran ring adopts a sofa conformation, the thia­zolidine ring adopts a twisted conformation and the pyrrolidine ring adopts an envelope conformation with the N atom as the flap. The pyrazole ring is essentially planar [maximum deviation = 0.002 (2) Å] and forms dihedral angles of 4.8 (1) and 39.0 (1)°, respectively, with the benzene rings attached to the N and C atoms. The acenapthylene ring system is approximately planar [maximum deviation = 0.058 (2) Å] and forms dihedral angles of 85.9 (1) and 48.5 (1)°, respectively, with the pyrollothia­zole and chromene ring systems. The mol­ecular conformation is stabilized by three weak intra­molecular C—H⋯O hydrogen bonds, which generate one S(8) and two S(6) ring motifs. In the crystal, pairs of C—H⋯O hydrogen bonds link centrosymmetrically related mol­ecules into dimers, generating R 2 2(14) ring motifs. The crystal packing also features pairs of C—H⋯π inter­actions, which link the dimers into a supra­molecular chain along the b axis.
doi:10.1107/S1600536813005825
PMCID: PMC3629526  PMID: 23634044
18.  (Z)-3-(2,4-Dichloro­benz­yl)-1,5-benzo­thia­zepin-4(5H)-one 
In the title compound, C16H11Cl2NOS, the seven-membered thia­zepine ring adopts a distorted twist-boat conformation. The dihedral angle between the mean plane of the benzothia­zepine ring system and the benzene ring is 78.6 (1)°. The mol­ecular conformation is stabilized by a weak intra­molecular C—H⋯Cl hydrogen bond, which generates an S(5) ring motif. In the crystal, pairs of N—H⋯O hydrogen bonds link inversion-related mol­ecules into dimers, generating R 2 2(8) ring motifs. The crystal packing also features alternating π–π inter­actions between benzothia­zepine benzene rings [inter-centroid distance = 3.740 (3) Å] and dichloro­benzene rings [inter-centroid distance = 3.882 (3) Å] to consolidate a three-dimensional architecture.
doi:10.1107/S1600536813007435
PMCID: PMC3629614  PMID: 23634101
19.  (E)-1-[(2-Amino-5-nitro­phen­yl)iminio­meth­yl]naphthalen-2-olate 
The title Schiff base compound, C17H13N3O3, crystallizes in a zwitterionic form and exists in a trans configuration about the C=N bond. The mol­ecule is slightly twisted, the dihedral angle between the benzene ring and naphthalene ring system being 10.80 (9)°. The nitro group is twisted relative to the plane of the benzene ring [dihedral angle = 8.88 (12)°]. Bifurcated intra­molecular N—H⋯N and N—H⋯O hydrogen bonds formed between iminium groups and amine N atoms and naphthalen-2-olate O atoms generate S(5) and S(6) ring motifs, respectively. In the crystal, neighbouring zwitterions are linked through weak C—H⋯O inter­actions, giving rise to screw chains along [010]. Mol­ecules in these chains are linked to those of an adjacent chains through N—H⋯O hydrogen bonds and weak C—H⋯O inter­actions, forming sheets parallel to the ac plane. O⋯C [2.895 (3) Å] short contacts and π–π inter­actions [centroid–centroid distance = 3.8249 (19) Å] are also observed.
doi:10.1107/S1600536810014923
PMCID: PMC2979134  PMID: 21579252
20.  Diaquadi-μ-formato-bis­{μ-2,2′-[propane-1,3-diylbis(nitrilo­methanylyl­idene)]diphenolato}cadmium(II)dinickel(II) dihydrate 
In the centrosymmetric title compound, [CdNi2(C17H16N2O2)2(HCOO)2(H2O)2]·2H2O, The NiII cation is chelated by a 2,2′-[propane-1,3-diylbis(nitrilo­methanylyl­idene)]diphen­olate (salpn) anion, and further coordinated by a formate anion and a water mol­ecule in a distorted NiN2O4 octa­hedral geometry. The CdII cation, located on an inversion center, is coordinated by four deprotonated hy­droxy groups from two salpn anions and two carboxyl­ate O atoms from formate anions in a distorted octa­hedral geometry. Both formate and salpn anions bridge the Cd and Ni cations, forming a trinuclear complex. Within the salpn anion, the benzene rings are twisted to each other at a dihedral angle of 61.46 (18)°. Inter­molecular O—H⋯O hydrogen bonding is present in the crystal structure. The lattice water mol­ecule is disorder over two positions with an occupancy ratio of 0.75:0.25.
doi:10.1107/S1600536812029583
PMCID: PMC3414165  PMID: 22904772
21.  2,2′-{[2-(2-Hy­droxy­phen­yl)-4-methyl­imidazolidine-1,3-di­yl]bis­(methyl­ene)}diphenol 
The asymmetric unit in the title compound, C24H26N2O3, comprises two independent mol­ecules (A and B). In molecule A, the central 2-hydroxyphenyl ring is inclined to the mean plane of the major component of the imidazolidine ring by 84.52 (14)°, and by 68.08 (9) and 47.48 (9)° to the outer phenol rings. The later are inclined to one another by 66.76 (9)° and by 78.12 (14) and 80.20 (14)° to the imidazoline ring mean plane. In molecule B, the central 2-hydroxyphenyl ring is inclined to the mean plane of the imidazolidine ring by 73.64 (10)°, and by 75.60 (8) and 38.32 (9)° to the outer phenol rings. The later are inclined to one another by 69.47 (9)° and by 82.60 (10) and 64.26 (10)° to the imidazolidine ring mean plane. In each of the independent mol­ecules, two intra­molecular O—H⋯N hydrogen bond form S(6) ring motifs. In disordered mol­ecule A, the O—H groups of the 2-hy­droxy­benzyl groups are also involved in intra­molecular O—H⋯O hydrogen bonds, with the O atom of the hy­droxy­phenyl group acting as the acceptor. In the crystal, A molecules are linked by pairs of O—H⋯O hydrogen bonds forming inversion dimers. These dimers are linked to the B molecules via O—H⋯O hydrogen bonds forming double-layered slabs lying parallel to the bc plane.
doi:10.1107/S1600536813019417
PMCID: PMC3793786  PMID: 24109373
22.  6,6′-Di-tert-butyl-4,4′-dimeth­oxy-2,2′-[1,3-diazinane-1,3-diylbis(methyl­ene)]diphenol 0.19-hydrate 
In the title hexa­hydro­pyrimidine derivative, C28H42N2O4·0.19H2O, the 1,3-diazinane ring has a chair conformation with a diequatorial substitution. The asymmetric unit contains one half-organic mol­ecule and a solvent water mol­ecule with occupany 0.095. The mol­ecule lies on a mirror plane perpendicular to [010] which passes through the C atoms at the 2- and 5-positions of the heterocyclic system. The partially occupied water mol­ecule is also located on this mirror plane. The dihedral angle between the planes of the aromatic rings is 17.71 (3)°. Two intra­molecular O—H⋯N hydrogen bonds with graph-set motif S(6) are present. No remarkable inter­molecular contacts exist in the crystal structure.
doi:10.1107/S1600536811053542
PMCID: PMC3254529  PMID: 22259475
23.  {6,6′-Dieth­oxy-2,2′-[2,2-dimethyl­propane-1,3-diylbis(nitrilo­methyl­idyne)]diphenolato}copper(II) monohydrate 
In the title complex, [Cu(C23H28N2O4)]·H2O, the CuII ion has a distorted planar geometry, coordinated by the N2O2 unit of the tetra­dentate Schiff base ligand. The asymmetric unit comprises one complex mol­ecule and a water mol­ecule of crystallization. The water H atoms form bifurcated O—H⋯(O,O) inter­molecular hydrogen bonds with the O atoms of the phenolate and eth­oxy groups with R12(5) and R12(6) ring motifs, which may, in part, influence the mol­ecular configuration. The dihedral angle between the two O—Cu—N coordination planes is 31.02 (6)° and the dihedral angle between the two benzene rings is 34.98 (7)°. In the crystal structure, mol­ecules are linked together by inter­molecular C—H⋯O inter­actions, forming extended chains along the a axis. The crystal structure is further stabilized by inter­molecular C—H⋯π and π–π [centroid–centroid = 3.5068 (13) Å] inter­actions.
doi:10.1107/S1600536809012859
PMCID: PMC2977574  PMID: 21583760
24.  4-[(E)-(2,4-Difluoro­phen­yl)(hydroxy­imino)meth­yl]piperidinium picrate 
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).
doi:10.1107/S1600536809035363
PMCID: PMC2970333  PMID: 21577832
25.  (±)-trans-6,6′-Dieth­oxy-2,2′-[cyclo­hexane-1,2-diylbis(nitrilo­methanylyl­idene)]diphenol monohydrate 
In the title hydrate, C24H30N2O4·H2O, the organic mol­ecule adopts an E conformation with respect to the azomethine double bonds. The cyclo­hexane ring is in a chair conformation. The dihedral angle between benzene rings is 79.6 (2)°. Two intra­molecular O—H⋯N hydrogen bonds are present. In the crystal, the components are linked by O–H⋯O hydrogen bonds and weak C—H⋯π inter­actions, generating a three-dimensional supramolecular architecture.
doi:10.1107/S1600536814000713
PMCID: PMC3998335  PMID: 24764896

Results 1-25 (537666)