Benz­aldehyde 2,4‐di­nitro­phenyl­hydrazone

Crystals of the title compound, C₁₃H₁₀N₄O₄, were obtained from a condensation reaction of benz­aldehyde and 2,4‐di­nitrophenyl­hydrazine. The mol­ecule assumes an approximately planar E configuration. Within the di­nitro­phenyl moiety, the average distance for the aromatic C—C bonds close to the imino group [1.417 (3) Å] is appreciably longer than the average distance for the other aromatic C—C bonds in the same phenyl ring [1.373 (3) Å]. This increased distance may be a result of the overlap of the non‐bonding orbital of the imino N atom with the π orbitals of the arene. It is likely that π–π stacking exists in the crystal structure.     

4‐(2,4‐Dinitro­phenyl­sulfanyl)­morpholine

In the title compound, C₁₀H₁₁N₃O₅S, the 2,4‐dinitro­phenyl fragment is connected by an S atom to the morpholine ring, which is in a chair conformation. The ortho‐ and para‐nitro groups are slightly twisted out of the plane of the benzene ring. The mol­ecules are linked into C(7) and C(10) chains by two inter­molecular C—H⋯O hydrogen bonds.     

Orthorhombic polymorphs of two trans‐4‐aminoazoxybenzenes

The two isomeric compounds 4‐amino‐ONN‐azoxy­benzene [or 1‐(4‐amino­phenyl)‐2‐phenyl­diazene 2‐oxide], i.e. the α isomer, and 4‐amino‐NNO‐azoxy­benzene [or 2‐(4‐amino­phenyl)‐1‐phenyl­diazene 2‐oxide], i.e. the β isomer, both C₁₂H₁₁N₃O, crystallized from a polar solvent in orthorhombic space groups, and their crystal and molecular structures have been determined using X‐ray diffraction. There are no significant differences in the bond lengths and valence angles in the two isomers, in comparison with their monoclinic polymorphs. However, the conformations of the mol­ecules are different due to rotation along the Ar—N bonds. In the α isomer, the benzene rings are twisted by 31.5 (2) and 14.4 (2)° towards the plane of the azoxy group; the torsion angles along the Ar—N bond in the β isomer are 24.3 (3) and 23.5 (3)°. Quantum‐mechanical calculations indicate that planar conformations are energetically favourable for both isomers. The N—H?O hydrogen bonds observed in both networks may be responsible for the deformation of these flexible mol­ecules.     

2,4‐Di­nitro­phenyl­hydrazones of 2,4‐di­hydroxy­benz­aldehyde, 2,4‐di­hydroxy­aceto­phenone and 2,4‐di­hydroxy­benzo­phenone

In 2,4‐di­hydroxy­benz­aldehyde 2,4‐di­nitro­phenyl­hydrazone N,N‐di­methyl­form­amide solvate {or 4‐[(2,4‐di­nitro­phenyl)­hydrazono­methyl]­benzene‐1,3‐diol N,N‐di­methyl­form­amide solvate}, C₁₃H₁₀N₄O₆·C₃H₇NO, (X), 2,4‐di­hydroxy­aceto­phenone 2,4‐di­nitro­phenyl­hydrazone N,N‐di­methyl­form­am­ide solvate (or 4‐{1‐[(2,4‐di­nitro­phenyl)hydrazono]ethyl}benzene‐1,3‐diol N,N‐di­methyl­form­amide solvate), C₁₄H₁₂N₄O₆·C₃H₇NO, (XI), and 2,4‐di­hydroxy­benzo­phenone 2,4‐di­nitro­phenyl­hydrazone N,N‐di­methyl­acet­amide solvate (or 4‐­{[(2,4‐di­nitro­phenyl)hydrazono]phenyl­methyl}benzene‐1,3‐diol N,N‐di­methyl­acet­amide solvate), C₁₉H₁₄N₄O₆·C₄H₉NO, (XII), the molecules all lack a center of symmetry, crystallize in centrosymmetric space groups and have been observed to exhibit non‐linear optical activity. In each case, the hydrazone skeleton is fairly planar, facilitated by the presence of two intramolecular hydrogen bonds and some partial N—N double‐bond character. Each molecule is hydrogen bonded to one solvent mol­ecule.     

3‐(1‐Hydroxy­ethyl­idene)‐1‐phenyl­pyrrolidine‐2,4‐dione

Analysis of C₁₂H₁₁NO₃ revealed a coplanar N‐substituted phenyl group on a pyrrolidine ring with two keto moieties and a hydroxy­ethyl­idene functionality. The hydroxy group forms part of a hydrogen‐bonding network characterized by a short intramolecular H?O distance of 1.81 (3) Å, and a longer intermolecular interaction with an H?O distance of 2.38 (3) Å. Both keto groups form additional intra‐ and intermolecular C—H?O contacts with H?O distances ranging from 2.26 to 2.41 Å.     

Diisopropyl­ammonium 2‐[(2,4‐dinitro­phenyl)­sulfanyl­amino­carbonyl]­benzoate

The structure of title compound, C₆H₁₆N⁺·C₁₄H₈N₃O₇S⁻, comprises discrete ions which are inter­connected by N—H⋯O⁻ and N—H⁺⋯O⁻ hydrogen bonds, leading to a neutral one‐dimensional network along [100]. These hydrogen bonds appear to complement the Coulombic inter­action and help to stabilize the structure further.     

Polymorphic di‐2‐pyridyl ketone 4‐nitro­phenyl­hydrazone (dpknph): the structure of β‐dpknph

A new polymorph of di‐2‐pyridyl ketone 4‐nitro­phenyl­hydrazone [alternative name: N‐(di­pyridin‐2‐ylmethyl­ene)‐N′‐(4‐nitro­phen­yl)hydrazine], C₁₇H₁₃N₅O₂, isolated from the filtrate of a sonicated acetonitrile solution of dpknph and CdCl₂, was found to crystallize in the monoclinic space group P2₁/c, in contrast to the known form which crystallizes in P2₁/n. The non‐coplanar mol­ecules pack in parallel stacks without any inter­molecular hydrogen‐bonding inter­actions. This packing pattern contrasts with the inter­locked inter­digitated packing seen in the previously known polymorph.     

Crystal polymorphs of 6‐[(phenylcarbamoyl)oxy]hexa‐2,4‐diyn‐1‐yl isonicotinate

The title compound, C₁₉H₁₄N₂O₄, was found to have two crystal polymorphs, in which the molecular structures of the diacetylenic compound are broadly similar. The main structural difference between the polymorphs concerns the intermolecular hydrogen‐bonding motifs adopted, namely a one‐dimensional zigzag polymer linked by N—H…N(py) (py is pyridine) interactions in polymorph I and a centrosymmetric dimeric motif formed by N—H…O=C interactions in polymorph II. The diacetylene cores of the molecules stack along the a and b axes in polymorphs I and II, respectively. It was found that only the molecular arrangement in polymorph II satisfies Baughman's criterion to afford polydiacetylenes (PDAs) by thermal annealing or irradiation with light. This predicted polymerization activity was confirmed by experiment.     

A comparative study of two polymorphs of bis(1‐hydroxy‐2‐methylpropan‐2‐aminium) carbonate

Alkanolamines have been known for their high CO₂ absorption for over 60 years and are used widely in the natural gas industry for reversible CO₂ capture. In an attempt to crystallize a salt of (RS)‐2‐(3‐benzoylphenyl)propionic acid with 2‐amino‐2‐methylpropan‐1‐ol, we obtained instead a polymorph (denoted polymorph II) of bis(1‐hydroxy‐2‐methylpropan‐2‐aminium) carbonate, 2C₄H₁₂NO⁺·CO₃²⁻, (I), suggesting that the amine group of the former compound captured CO₂ from the atmosphere forming the aminium carbonate salt. This new polymorph was characterized by single‐crystal X‐ray diffraction analysis at low temperature (100 K). The salt crystallizes in the monoclinic system (space group C2/c, Z = 4), while a previously reported form of the same salt (denoted polymorph I) crystallizes in the triclinic system (space group P, Z = 2) [Barzagli et al. (2012). ChemSusChem, 5 , 1724–1731]. The asymmetric unit of polymorph II contains one 1‐hydroxy‐2‐methylpropan‐2‐aminium cation and half a carbonate anion, located on a twofold axis, while the asymmetric unit of polymorph I contains two cations and one anion. These polymorphs exhibit similar structural features in their three‐dimensional packing. Indeed, similar layers of an alternating cation–anion–cation neutral structure are observed in their molecular arrangements. Within each layer, carbonate anions and 1‐hydroxy‐2‐methylpropan‐2‐aminium cations form planes bound to each other through N—H…O and O—H…O hydrogen bonds. In both polymorphs, the layers are linked to each other via van der Waals interactions and C—H…O contacts. In polymorph II, a highly directional C—H…O contact (C—H…O = 156°) shows as a hydrogen‐bonding interaction. Periodic theoretical density functional theory (DFT) calculations indicate that both polymorphs present very similar stabilities.     

3‐Hydro­xy‐6‐[(4‐hydroxy­phenyl­amino)­methyl­ene]­cyclo­hexa‐2,4‐dienone and 2‐hydroxy‐6‐[(4‐hydroxy­phenyl­amino)­methyl­ene]­cyclo­hexa‐2,4‐dienone

The title compounds, both C₁₃H₁₁NO₃, exist as the keto–amine tautomers, and the formal hydroxyl H atoms, which display strong intramolecular hydrogen bonds, are located on the N atoms. This is a verification of the preference for the keto–amine tautomeric form in the solid state. The 2‐hydroxy isomer has two independent mol­ecules, with the mol­ecules linked by intramolecular N—H⋯O and O—H⋯O and intermolecular O—H⋯O hydrogen bonds into three‐dimensional networks.     

π‐Stacked hydrogen‐bonded dimers in 2‐(2‐nitro­phenyl­amino­carbonyl)­benzoic acid,and hydrogen‐bonded sheets in orthorhombic and monoclinic polymorphs of 2‐(4‐nitro­phenyl­amino­carbonyl)­benzoic acid

Molecules of 2‐(2‐nitrophenylaminocarbonyl)benzoic acid, C₁₄H₁₀N₂O₅, are linked into centrosymmetric R(8) dimers by a single O—H⋯O hydrogen bond [H⋯O = 1.78 Å, O⋯O = 2.623 (2) Å and O—H⋯O = 178°] and these dimers are linked into sheets by a single aromatic π–π stacking interaction. The isomeric compound 2‐(4‐nitrophenylaminocarbonyl)benzoic acid crystallizes in two polymorphic forms. In the orthorhombic form (space group P2₁2₁2₁ with Z′ = 1, crystallized from ethanol), the mol­ecules are linked into sheets of R(22) rings by a combination of one N—H⋯O hydrogen bond [H⋯O = 1.96 Å, N⋯O = 2.833 (3) Å and N—H⋯O = 171°] and one O—H⋯O hydrogen bond [H⋯O = 1.78 Å, O⋯O = 2.614 (3) Å and O—H⋯O = 173°]. In the monoclinic form (space group P2₁/n with Z′ = 2, crystallized from acetone), the mol­ecules are linked by a combination of two N—H⋯O hydrogen bonds [H⋯O = 2.09 and 2.16 Å, N⋯O = 2.873 (4) and 2.902 (3) Å, and N—H⋯O = 147 and 141°] and two O—H⋯O hydrogen bonds [H⋯O = 1.84 and 1.83 Å, O⋯O = 2.664 (3) and 2.666 (3) Å, and O—H⋯O = 166 and 174°] into sheets of some complexity. These sheets are linked into a three‐dimensional framework by a single C—H⋯O hydrogen bond [H⋯O = 2.45 Å, C⋯O = 3.355 (4) Å and C—­H⋯O = 160°].     

3‐(4‐Chloro­benzoyl)‐7‐(N,N‐di­methyl­amino)‐1‐phenyl­indolizine and 3‐(2,4‐di­chloro­benzoyl)‐7‐(N,N‐di­methyl­amino)‐1‐phenyl­indolizine

In both of the title compounds, C₂₃H₁₉ClN₂O, (I), and C₂₃H₁₈Cl₂N₂O, (II), the molecular packing is influenced by weak intermolecular C—H⋯O and C—H⋯π interactions, but despite the chemical similarity of the compounds, the packing in (II) is entirely different from that observed in (I).     

Two polymorphs of 1,8‐dichloroanthracene

A second, monoclinic, polymorph of the title compound, C₁₄H₈Cl₂, has been found. In addition to the structure of this monoclinic form, the structure of the previously described orthorhombic form [Desvergne, Chekpo & Bouas‐Laurent (1978). J. Chem. Soc. Perkin Trans. 2, pp. 84–87; Benites, Maverick & Fronczek (1996). Acta Cryst. C 52 , 647–648] has been redetermined at low temperature and using modern methods. The low‐temperature structure of the orthorhombic form is of significantly higher quality than the previously published structure and additional details can be derived. A comparison of the crystal packing of the two forms with a focus on weak intermolecular C—H...Cl interactions shows the monoclinic structure to have one such interaction linking the molecules into infinite ribbons, while two crystallographically independent C—H...Cl interactions give rise to an interesting infinite three‐dimensional network in the orthorhombic crystal form.     

Comparison of the two anomers of methyl 2‐(N‐benzyl­amino)‐2,3‐di­deoxy‐4,6‐O‐phenyl­methyl­ene‐3‐C‐phenyl­sulfonyl‐d‐gluco­pyran­oside

The title compounds, the α and β anomers of methyl 2‐(N‐benzyl­amino)‐2,3‐di­deoxy‐4,6‐O‐phenyl­methyl­ene‐3‐C‐phenyl­sulfonyl‐d ‐gluco­pyran­oside, C₂₇H₂₉NO₆S, belong to the class of deoxy­amino‐­sugars prepared by the addition of amines at C2. The endocyclic bond lengths of the pyran­ose ring in the α anomer are shorter than the corresponding bonds in the β anomer. The pyran­ose ring is in the chair form in the former, while it is in the boat form in the latter. These observed differences could be attributed to the C2 substitution of a bulky group. The phenyl­sulfonyl and benzyl­amino groups are in equatorial positions in the α anomer, while the benzyl­amino group is axial in the β anomer.     

2‐Amino derivatives of 5‐nitro­phenyl­acet­amide

The structures of the potential non‐linear optical (NLO) materials N‐[2‐(iso­propyl­amino)‐5‐nitro­phenyl]­acet­amide, (I) C₁₁H₁₅N₃O₃, and N‐[2‐(butyl­amino)‐5‐nitro­phenyl]­acet­amide, (II) C₁₂H₁₇N₃O₃, have been investigated by X‐ray analysis. To compare them with the structure of N‐[2‐(di­methyl­amino)‐5‐nitro­phenyl]­acet­amide, (III) C₁₀H₁₃N₃O₃, a known NLO compound, we had to redetermine the structure of (III), since it was described only briefly in the literature. There are two mol­ecules in the asymmetric unit of compound (I), which have different orientations of the substituents with respect to the benzene ring. The packing of mol­ecules in (II) and (III) contains stacks but both (I) and (II) crystallize in a centrosymmetric space group, which renders them inappropriate for NLO applications.     

Two three‐dimensional networks in two polymorphs of biphenyl‐4,4′‐diaminium bis(3‐carboxy‐4‐hydroxybenzenesulfonate) dihydrate

Two polymorphs of biphenyl‐4,4′‐diaminium bis(3‐carboxy‐4‐hydroxybenzenesulfonate) dihydrate, C₁₂H₁₄N₂²⁺·2C₇H₅O₆S⁻·2H₂O, have been obtained and crystallographically characterized. Polymorph (I) crystallizes in the space group P2₁/c with Z′ = 2 and polymorph (II) in the space group P with Z′ = 0.5. The benzidinium cation in (II) is located on a crystallographic inversion centre. In both (I) and (II), the sulfonic acid H atoms are transferred to the benzidine N atoms, forming dihydrated 1:2 molecular adducts (base–acid). In the crystal packings of (I) and (II), the component ions are linked into three‐dimensional networks by combinations of X—H...O (X = O, N and C) hydrogen bonds. In addition, π–π interactions are observed in (I) between inversion‐related benzene rings [centroid–centroid distances = 3.632 (2) and 3.627 (2) Å]. In order to simplify the complex three‐dimensional networks in (I) and (II), we also give their rationalized topological analyses.     

A novel trinuclear palladium cluster compound: di‐μ3‐chloro‐tris­[chloro(tri­phenyl­phosphine‐P)­palladium] acetone solvate

The title triangular tripalladium cluster, [Pd₃­Cl₅­(C₁₈­H₁₅P)₃]·­C₃H₆O, (I), has a trigonal‐bipyramidal framework of Pd₃(μ₃‐Cl)₂, with the two Cl atoms in apical positions. Each Pd atom in the framework has two additional coordination sites to establish square‐planar cis‐PdL₂(μ₃‐Cl)₂ geometry. Three P atoms are located on the same side of the plane defined by the Pd₃ triangle, which leads to a pseudo‐C_3v symmetry for the core framework of Pd₃(μ₃‐Cl)₂P₃Cl₃. The average Pd—Cl distance trans to PPh₃ is 2.473 (8) Å, which is significantly longer than the average Pd—Cl distance of 2.294 (4) Å for those trans to terminal Cl, due to the strong trans effect of a P atom compared with a Cl atom. Compound (I) has 49 valence electrons and shows a rhombic electron‐spin resonance signal, indicating an S = ½ ground state.     

Two polymorphs of 20‐desmethyl‐β‐carotene

Two polymorphs of 20‐desmethyl‐β‐carotene (systematic name: 20‐nor‐β,β‐carotene), C₃₉H₅₄, in monoclinic and triclinic space groups, were formed in the same vial by recrystallization from pyridine and water. Each polymorph crystallizes with the complete molecule as the asymmetric unit, and the two polymorphs show differing patterns of disorder. The β end rings of both polymorphs have the 6‐s‐cis conformation, and are twisted out of the plane of the polyene chain by angles of −53.2 (8) and 47.3 (8)° for the monoclinic polymorph, and −43.6 (3) and 56.1 (3)° for the triclinic polymorph. The cyclohexene end groups are in the half‐chair conformation, but the triclinic polymorph shows disorder of one ring. Overlay of the molecules shows that they differ in the degree of nonplanarity of the polyene chains and the angles of twist of the end rings. The packing arrangements of the two polymorphs are quite different, with the monoclinic polymorph showing short intermolecular contacts of the disordered methyl groups with adjacent polyene chain atoms, and the triclinic polymorph showing π–π stacking interactions of the almost parallel polyene chains. The determination of the crystal structures of the two title polymorphs of 20‐desmethyl‐β‐carotene allows information to be gained regarding the structural effects on the polyene chain, as well as on the end groups, versus that of the parent compound β‐carotene. The absence of the methyl group is known to have an impact on various functions of the title compound.     

Conformational preferences and supramolecular aggregation in 2‐nitro­phenyl­thiol­ates: 2‐nitro­phenyl‐β‐d‐thio­galacto­pyran­oside

In the title compound, C₁₂H₁₅NO₇S, the molecular conformation shows a concerted disrotatory twist of the nitro group and the galactose fragment out of the plane of the aryl ring. The mol­ecules are linked by O—H?O hydrogen bonds [O?O range 2.725 (2)–3.024 (2) Å and O—H?O range 155–175°] to form a three‐dimensional framework.