Structures of Three Chalcones Derived from 6-Methoxy-2-naphthaldehyde

Abstract  In the molecular structures of three new structurally related chalcone derivatives, namely (2E)-1-(2-hydroxyphenyl)-3-(6-methoxy-2-naphthyl)prop-2-en-1-one, C₂₀H₁₆O₃, I, (2E)-1-(2-chloropyridin-4-yl)-3-(6-methoxy-2-naphthyl)prop-2-en-1-one, C₁₉H₁₄ClNO₂, II, and (2E)-3-(6-methoxy-2-naphthyl)-1-pyridin-4-ylprop-2-en-1-one, III, C₁₉H₁₅NO₂, the configuration of the keto group is syn with respect to the olefinic double bond. In all three structures the molecules pack with weak intermolecular C–H···O interactions utilizing both the methoxy and keto oxygen’s in I, the methoxy oxygen in II and the keto oxygen in III. These interactions link the molecules into chains diagonally along the (011) plane of the unit cell in I and III and along the (010) plane in II. The dihedral angle between the phenyl and 2-napthyl rings in I is 31.7(3)°. In II and III the dihedral angle between the pyridyl and 2-naphthyl rings is 14.4(9)° and 1.8(9)°, respectively. C–H···O hydrogen bonding interactions influence these twist angles of these rings in I–III while weak π–π stacking interactions between naphthyl rings in I and III and also between pyridyl and naphthyl rings in II help stabilize crystal packing. [I: P2 ₁ /c, a = 7.6635(4) ?, b = 11.8047(6) ?, c = 16.7584(7) ?, β = 99.271(5)°, V = 1496.25(13) ?³; II: Pbca, a = 14.1424(4) ?, b = 6.0957(2) ?, c = 33.1458(11) ?, V = 2857.43(16) ?³; III: P2 ₁ /c, a = 11.5155(4) ?, b = 6.0020(2) ?, c = 22.4645(8) ?, β = 103.002(4)°, V = 1512.85(9) ?³]. Index Abstract  Crystal structures from three Chalcones derived from 6-methoxy-2-naphthaldehyde are reported and their geometric and packing parameters described.     

Structural Characterization of Di- and Mono-Imidazolyl-Substituted 1,8-Naphthyridine Derivatives

Abstract  Two imidazolyl derived 1,8-naphthyridine compounds (2,7-diimidazolyl-1,8-naphthyridine (a), and 2-benzimidazolyl-5,7-dimethyl-1,8-napthyridine (b)) were synthesized and structurally characterized by X-ray crystallography. The compound a co-crystallizes with one ethanol and two water molecules to give compound 1. Compound 1 crystallizes in the triclinic, space group P-1, with a = 6.943(2) ?, b = 9.009(3) ?, c = 13.760(3) ?, α = 96.793(2)°, β = 97.431(3)°, γ = 107.080(2)°, V = 804.6(4) ?³, Z = 2. Compound 1 forms a 3D interpenetrated network through hydrogen bonds. Compound b co-crystallizes with three and one half water molecules to form 2. Compound 2 crystallizes in the monoclinic, space group C2/c, with a = 24.926(8) ?, b = 10.608(3) ?, c = 16.751(5)?, β = 110.133(4)°, V = 4159(2) ?³, Z = 8. The free water molecules form six-membered rings, these water rings connect the naphthyridine to form one dimensional chain when viewed from b axis. The naphthyridyl rings in a and b axis are connected through C–H···π, and π–π interactions, due to the weak interactions the compound shows 3D network structure. Graphical Abstract  Due to the weak interactions, the naphthyridine derivatives showed 3D network structure.      

Crystal Structure of 2-<Emphasis Type="Italic">Exo</Emphasis>-Phenyl-2,3,4,5-Tetrahydro-1,4-Epoxinafto[1,2-b]azepine

Abstract  

The title compound, C₂₀H₁₇NO, crystallizes in the orthorhombic P2₁2₁2₁ space group with unit cell parameters a = 7.6903(7) ?, b = 18.979(2) ?, c = 19.753(2) ?, with two crystallographically independent molecules in the asymmetric unit, which differ from one another in the slight rotation of the phenyl ring; this allows the formation of three internal hydrogen bonds, two of the type C–H···N and one of the type C–H···O, in one of the molecules, in contrast with only two of the type C–H···N in the other. The compound is rich in aromatic π rings and therefore the crystal packing is entirely dominated by cohesive weak C–H···π interactions among neighboring molecules producing an efficient packing with 71.2% of occupied space.     

Hydrogen Bonded 3D Supramolecular Architectures of Three Saccharinate Salts

Abstract  

Three saccharinate salts (2-aminopyrimidine): (saccharin) (1), (4-phenylthiazol-2-amine): (saccharin) (2), and (2-methylquinoline): (saccharin) (3) were prepared and structurally characterized by X-ray crystallography. Salt 1 crystallizes in the monoclinic, space group P2(1)/c, with a = 7.1782(9) ?, b = 13.5105(16) ?, c = 12.2251(12) ?, β = 93.3410(10)°, V = 1183.6(2) ?³, Z = 4. Compound 2 crystallizes in the triclinic, space group P-1, with a = 7.4584(7) ?, b = 8.6930(9) ?, c = 12.9179(14) ?, α = 108.952(2)°, β = 91.7510(10)°, γ = 97.2280(10)°, V = 783.57(14) ?³, Z = 2. Compound 3 crystallizes in the monoclinic, space group P2(1)/c, with a = 7.781(8) ?, b = 19.4209(19) ?, c = 10.9719(12) ?, β = 107.7390(10)°, V = 1579.2(16) ?³, Z = 4. The different hydrogen bonding interaction modes of the saccharinate anions and the cations lead to 3D network structure, 3D staircase structure, and 3D ABAB layer structure for 1, 2, and 3 respectively. Despite variations in the cation shape on the aromatic N–heterocyclic compounds, there all existed strong intermolecular N–H⋯O(carbonyl) hydrogen bonds. In compounds 1, and 3 the N⁺–H⋯O interaction between the N⁺–H group of the cation and the C=O group of the saccharinate anion is the most important interaction in this family of salts. However, in 2, there was a N–H⋯O interaction between the amino proton and the C=O group of the saccharinate anion. At the next level, the aromatic C–H proton interacts with the sulfonyl O atom. There are also π–π interactions in compounds 1–2, there is CH₃–π interaction in 3. Under these interactions the three compounds exhibit synthons I–III respectively. These interactions are responsible for the high-yielding supramolecular assembly of N-containing aromatic bases and the saccharinate into salts.     

Structural Characterization of New Compound from the Ring-Opening Reaction of 3-(1H-1,2,4-triazol-1-yl)-1,5-Benzothiazepine with Phenylonitrile Oxide

Abstract  

The crystal structure of the product (Z)-2-((Z)-((Z)-1,3-diphenyl-2-(1H-1,2,4-triazol-1-yl)allylidene)amino)phenyl N-hydroxybenzimidothioate (4) was obtained by single crystal X-ray diffraction. The title compound, C₃₀H₂₃N₅OS (4), crystallizes in the triclinic space group, P-1, with unit cell parameters a = 8.3306(17) ?, b = 11.394(2) ?, c = 14.560(3) ?, α = 78.75(3)o, β = 89.96(3)o, γ = 70.56(3)o, Z = 2. In the crystal structure, adjacent molecules are linked by O–H···N hydrogen bonds. H-bonds and π–π stacking are the main non-bonding interactions in the molecular structure and give support to molecular packing stability. In addition, the structure is supported by a weak intermolecular C–H···Cg π-ring interaction. Detail of the synthesis, structures, and spectroscopic properties of the title compound is discussed.     

Structure of Methyl N-(4-methoxyphenylmethyl)-N′-cyano-carbamimidothioate and Methyl N-[1-(phenylmethyl)-4-piperidinyl]-N′-cyanocarbamimidothioate

Abstract  

The title compounds, Methyl N-(4-methoxyphenylmethyl)-N′-cyanocarbamimidothioate, I, and Methyl N-[1-(phenylmethyl)-4-piperidinyl]-N′-cyanocarbamimidothioate, II, have been designed and synthesized for use as new potential organic molecular electronic materials. The crystal structure of I and II were determined with crystal data (I: Monoclinic, P2₁/c, a = 4.746(2) ?, b = 5.737(3) ?, c = 17.399(7) ?, β = 91.667(7)o, R _all = 0.0703; II: Orthorhombic, Pna2₁, a = 18.209(8) ?, b = 11.463(5) ?, c = 7.539(3) ?, β = 90.00 o, R _all = 0.0481). N–H···N hydrogen bonds were responsible for the formation of one-dimensional zigzag molecular chains of I, and trifurcated hydrogen-bonded molecular chains were indicated in structure of II. C–H···π and C–H···N hydrogen bonds were found in both structures. All these types of interaction together form an extended three-dimensional network and stabilize the title crystals.     

Pseudo-Merohedral Twinning in the Structure of the Hydrated 1:1 Proton-Transfer Compound of 5-Sulfosalicylic Acid with 4-Aminopyridine

Abstract  

The structure of the pseudo-merohedrally twinned crystal of the 1:1 proton-transfer compound of 5-sulfosalicylic acid (3-carboxy-4-hydroxybenzenesulfonic acid) with 4-aminopyridine: 4-aminopyridinium 3-carboxy-4-hydroxybenzenesulfonate sesquihydrate has been determined at 180 K and the hydrogen-bonding pattern is described. Crystals of the compound are monoclinic with space group P2₁/c, with unit cell dimensions a = 35.2589(8), b = 7.1948(1), c = 24.5851(5) ?, β = 110.373(2)°, and Z = 16. The monoclinic asymmetric unit comprises four cation–anion pairs and six water molecules of solvation with only the pyridinium cations having pseudo-symmetry as a result of inter-cation aromatic ring π–π stacking effects. Extensive hydrogen bonding gives a three-dimensional framework structure.     

Synthesis and Crystal Structure of Nickel(II) Complex with 2,2′-Biimidazole and 4-Aminobenzoic Acid

Abstract  The Ni(II) complex, [Ni(H₂biim)₂(PABA)₂]Cl₂·2H₂O, H₂biim being 2,2′-biimidazole, PABA being 4-aminobenzoic acid has been synthesized and the crystal structure determined using X-ray crystallography. The complex crystallizes in triclinic system, space group P − 1 with unit cell parameters a = 8.3920(9) ?, b = 9.8436(11) ?, c = 9.8874(11) ?, α = 94.862(2)°, β = 109.142(2)°, γ = 90.992(2)°, V = 767.95(15) ?³ and Z = 1. The molecules of the complex in the crystal assemble by way of N–H⋯Cl, O–H⋯Cl, O–H⋯O hydrogen bonds as well as π–π stacking interactions to provide a two-dimensional supramolecular structure. Index Abstract  Synthesis and Crystal Structure of Nickel(II) Complex with 2,2′-Biimidazole and 4-Aminobenzoic Acid Yanping Li and Pin Yang* The molecules of the title complex [Ni(H₂biim)₂(PABA)₂]Cl₂·2H₂O in the crystal assemble by way of N–H⋯Cl, O–H⋯Cl, O–H⋯O hydrogen bonds as well as π–π stacking interactions to provide a two-dimensional supramolecular structure.      

Structures of Two (<Emphasis Type="Italic">E</Emphasis>)-3-Substituted Cinnamoylbenzotriazole 1-Oxides

Abstract  

The molecule of (E)-3-(3-MeOC₆H₄CH=CHCO)-benzotriazole 1-oxide, 2, has a very near planar structure, while the 2-nitrophenyl ring is rotated out of the plane of the remaining atoms in (E)-3-(2-O₂NC₆H₄CH=CHCO)-benzotriazole 1-oxide, 1. The nitrogen oxide bond lengths in 1 and 2 are 1.258 (6) and 1.2683 (15) ?, respectively, and are in the region found for related compounds. There are no strong intermolecular hydrogen-bonds in either compound, instead there are weak C–H···O intermolecular hydrogen-bonds and π···π stacking interactions in 1, and C–H···O, C–H···π, and π···π stacking interactions in 2. Different three-dimensional arrays are generated in each case. Compound 1 crystallises in the orthorhombic space group Pna2₁, with a = 25.061 (2) ?, b = 3.6997 (2) ?, c = 14.2623 (12) ? and Z = 4. Compound 2 crystallises in the triclinic space group P-1, with a = 5.7297 (3) ?, b = 10.8440 (6) ?, c = 11.4965 (6) ?, α = 89.689 (3)°, β = 76.019 (3)°, γ = 75.047 (3)°, Z = 2.     

5-Pyridine 4-yl-3H-(1,3,4) Oxadiazole-2 Thione Hydrochloride Monohydrate, (I), and 4 [5-Ethylsulfanyl)-(1,3,4) Thiadiazole-2-yl]-Pyridinium Perchlorate, (II)

Abstract  

The title compounds C₇H₈ClN₃O₂S, (I), and C₉H₁₀ClN₃O₄S_2, (II), both crystallize in monoclinic space group P2₁ /c with unit cell parameters (I) a = 7.9402(7), b = 10.6312(9), c = 11.7626(10), ?, β = 99.271(5)°, Z = 4 and (II) a = 5.1439(2), b = 9.0636(4), c = 27.1814 (7), ?, β = 95.116(2)°, Z = 4. In (I) the molecule consists of a 5-pyridine-4-yl group bonded to the carbon atom at the 5 position of (1, 3, 4) oxadiazole-2 thione hydrochloride monohydrate. The angle between the mean planes of the oxadiazole and pyridine rings is 9.6(6)°. Crystal packing in (I) is stabilized by strong N–H···O hydrogen bonds in concert with a solvent water molecule and weak O–H···Cl, O–H···S, N–H···Cl intermolecular interactions. The crystal structure of compound (II) consists of 4 [5-ethylsulfanyl)-(1, 3, 4) thiadiazole-2-yl]-pyridinium perchlorate, (C₉H₁₀N₃S₂)⁺(ClO₄)⁻, cation–anion pairs, containing strong intermolecular N–H···O hydrogen bonds and weak C–H···O and N–H···O intermolecular interactions operating between the ionic species that form a cooperative hydrogen-bonded, infinite chain O–H···O–H···O–H network which generates a sheet motif structure in the unit cell. It is also supported by weak intermolecular Cg···Cg π–π and Cl–O···Cg π-ring interactions which gives additional support to molecular packing stability in the unit cell. Geometry optimized MOPAC AM1 computational calculations on each compound provides support to the structural features in their respective crystal structures.     

Propeller-like Conformation of Diphenylacetic Acid

Abstract Crystal structure of diphenylacetic acid has been solved by X-ray diffraction. The crystals are monoclinic, space group P2₁/c, with a = 12.254(4) ?, b = 7.2260(8) ?, c = 17.521(4) ?, β = 133.38(1)°, Mr = 212.24, V = 1127.6(5) ?³, Z = 4 and R = 0.045. A strong hydrogen bond links the molecules in dimers. The dimers are connected by weaker C–H···π and π···π interactions. A calculation was performed for the isolated molecule and for the dimer within the Hartree-Fock (HF) level with a 6-311G(d) basis set. In both calculations, the minimum of the energy is achieved with the phenyl rings assuming a more symmetric arrangement around the central carboxylic plane than is experimentally observed. Graphical Abstract In diphenylacetic acid the molecules are coupled in dimers by a strong hydrogen bonds. Weaker intermolecular interactions involving the aromatic ring π systems join the dimers together. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Synthesis, Characterization, and Crystal Structures of 3-bromo-N′-(2-methoxybenzylidene)benzohydrazide and N′-(2-methoxybenzylidene)-3,4-methylenedioxybenzohydrazide

Abstract  

Two new hydrazone compounds, 3-bromo-N′-(2-methoxybenzylidene)benzohydrazide (1) and N′-(2-methoxybenzylidene)-3,4-methylenedioxybenzohydrazide (2), have been synthesized and characterized by elemental analysis, IR, and single crystal X-ray diffractions. Compound (1) crystallizes in the triclinic space group P1 with unit cell dimensions a = 8.4088(5) ?, b = 8.5398(5) ?, c = 10.6572(6) ?, α = 90.356(3)°, β = 102.868(3)°, γ = 97.987(3)°, V = 738.28(7) Ǻ³, Z = 2, R ₁ = 0.0406, and wR ₂ = 0.0804. Compound (2) crystallizes in the tetragonal space group P4₁ with unit cell dimensions a = b = 9.792(4) ?, c = 15.788(6) ?, V = 1513.8(10) Ǻ³, Z = 4, R ₁ = 0.0415, and wR ₂ = 0.0818. The molecules of both compounds display E configurations with respect to the C=N double bonds. In the crystal structure of (1), molecules are linked through N–H···O hydrogen bonds, forming chains running along the b axis. In the crystal structure of (2), molecules are linked through N–H···O hydrogen bonds, forming chains running along the c axis.     

Structures of two N-{2-([(5-amino-1,3,4-thiadiazol-2-yl)difluoromethyl]-4-halophenyl}acetamides

Abstract  

The compounds, N-{2-[(5-amino-1,3,4-thiadiazol-2-yl)difluoromethyl]-4-chlorophenyl}acetamide (1: X = Cl) and N-{2([(5-amino-1,3,4-thiadiazol-2-yl)difluoromethyl]-4-bromo-phenyl}acetamide (1: X = Br), are isostructural. The molecules are near ‘‘V’’ shaped with the angles between the two aromatic planes ca. 84° in each case. The various intermolecular interactions, namely N–H···O, N–H···N, N–H···F, and C–H···N hydrogen bonds and C–H···π, C–Cl···π and C–O···π interactions, generate 3-D arrays. Compound (1: X = Cl) crystallizes in the monoclinic space group P21/c with a = 16.9032(7) ?, 10.2193(4) ?, c = 7.5227(4) ?, β = 100.179(3)° and Z = 4. Compound (1: X = Br) crystallizes in the monoclinic space group P21/c with a = 17.2119(4) ?, 10.2167(2) ?, c = 7.5677(2) ?, β = 100.326(2)° and Z = 4.     

Crystal and Molecular Structure of the 1:2 Adduct Formed Between <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>′-Butylenebis(imidazole) and Carboxylic Acid Derivatives

Abstract  

Two imidazolyl derived complexes [N,N′-butylenebis(imidazole): (fumaric acid)₂ (1), and N,N′-butylenebis(imidazole): (2,4,6-trinitrophenol)₂ (2)] were prepared and structurally characterized by X-ray crystallography. Compound 1 crystallizes in the triclinic, space group P−1, with a = 5.9990(12) ?, b = 8.1772(16) ?, c = 10.419(2) ?, α = 86.88(2)°, β = 84.73(3)°, γ = 77.03(4)°, V = 495.67(17) ?³, Z = 1. For 1, two dimensional network structure is formed through imidazolium moieties forming hydrogen bonds to di-ionic carboxylate groups of fumarate chains. In the same network layers and adjacent layers, C–H···O contact also accompanies the N⁺–H···O⁻ hydrogen bonds, all these lead the extended architecture to show a three-dimensional lamellar structure. Compound 2 crystallizes in the triclinic, space group P − 1, with a = 7.0236(14) ?, b = 8.2831(17) ?, c = 12.053(2) ?, α = 106.05(4)°, β = 99.13(2)°, γ = 98.84(3)°, V = 650.8(2) ?³, Z = 1. In 2, two parallel imidazolium cations and two antiparallel 2,4,6-trinitrophenolate anions formed 32-membered rings through hydrogen bonding interaction, these rings extended along the c axis direction to form one dimensional railway structure. Adjacent parallel railways connect further through C–H···O hydrogen bonds between the 2-CH of the imidazole ring and the NO₂ group O atoms. These weak interactions combined, the complex showed 3D layer structure.     

Self-Assembled Hydrogen-Bonding Chains of Copper(II) 2-Nitrobenzoate with Nicotinamide

Abstract  

The synthesis, spectral characterization and crystal structure of two new nitrobenzoatocopper(II) complexes, namely, [Cu₂(2-O₂Nbz)₄(nia)₂]·ACN (1) and [Cu₂(2-O₂Nbz)₄(ACN)₂] (2) (where 2-O₂Nbz = 2-nitrobenzoate, nia = nicotinamide and ACN = acetonitrile) are reported. The complexes 1 and 2 form dinuclear units of the paddle-wheel type around the crystallographic inversion centers. The copper ions are bridged by four 2-nitrobenzoate anions and the neutral N-donor ligands, viz. nicotinamide in 1 and acetonitrile in 2, are coordinated at apical positions. Selected geometric parameters of both complexes are compared with values for related tetra-2-nitrobenzoate complexes of copper(II) as well as the other dimeric copper(II) carboxylates with apical nicotinamide and acetonitrile ligands. The molecules of 1 are linked with N–H···O and C–H···O hydrogen bonds. The π–π stacking interactions in 1 are observed between benzene rings of 2-nitrobenzoate anions and pyridine rings of nicotinamide and also between acetonitrile molecules and benzene rings of 2-nitrobenzoate anions. The C–H···O hydrogen-bonds and CH/π interactions are observed in crystal structure of 2.     

Syntheses and Crystal Structures of Two New Cadmium(II) and Nickel(II) Complexes with 1,4-Phenylenediacetate and 2,2′-Bipyridyl-Like Ligands

Abstract  

Two new complexes, namely [Cd(PDA)_0.5(2,2′-bpy)Cl](H₂PDA) (1) and [Ni(PDA)(phen)(H₂O)]₂ (2) (H₂PDA = 1,4-phenylenediacetic acid, 2,2′-bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline), have been synthesized and characterized by elemental analysis, IR spectra and X-ray crystal diffraction. Single-crystal X-ray diffraction analysis shows that complex 1 crystallizes in the triclinic space group P-1 with unit cell dimensions a = 8.760 (4) ?, b = 11.190 (5) ?, c = 13.917 (7) ?, α = 110.383 (5)°, β = 101.736 (5)°, γ = 100.612 (5)°, V = 1202.8 (10) ?³, Z = 2, R ₁ = 0.0314 and wR ₂ = 0.0898. Complex 2 crystallizes in the monoclinic space group P2(1)/n with unit cell dimensions a = 9.911 (3) ?, b = 17.924 (6) ?, c = 10.638 (4) ?, β = 94.998 (5)°, V = 1882.7 (11) ?³, Z = 2, R ₁ = 0.0397 and wR ₂ = 0.1150. In complex 1, Cd(II) ions are alternately bridged by PDA ligands and chloride ions into 1D chains and the PDA ligands display trans-configuration. Complex 2 is a dimer and two Ni(II) ions are linked by two PDA ligands with cis-configuration, resulting in a cyclic structure. In spite of these differences, both in complexes 1 and 2 there are π–π stacking interactions and hydrogen bonding to make them 3D supramolecular frameworks.     

Crystal and Molecular Structure of 4-Aminobenzohydrazide

Abstract  

The molecule of 4-aminobenzohydrazide is essentially planar and geometric parameters conform to literature precedents. Supramolecular N–H···O and N–H···N interactions combine to link molecules of 4-aminobenzohydrazide into a three-dimensional network. Weaker N–H···N and N–H···π interactions consolidate the structure. The compound crystallizes in the monoclinic space group P2₁/n with a = 5.411(2) ?, b = 14.000(6) ?, c = 9.894(4) ?, β = 103.917(7)o, and Z = 4.     

Orthorhombic Polymorphs of 1-Phenyl-3-(3-Hydroxyphenyl)-2-Propen-1-One

Abstract  

Chalcones, 1,3-diphenyl-2-propene-1-ones, exist naturally and synthetically, and are characterized by the linkage of two aromatic rings joining a three carbon α-β-unsaturated carbonyl entity. We report the observation of two new polymorphs of a hydroxy chalcone, C₆H₅–CO–CH=CH–C₆H₄ (m-OH), identified as a result of a Claisen–Schmidt synthesis and manual screening technique. One polymorph of this compound has been reported previously and exists in the monoclinic system, space group P2/n, with unit cell parameters a = 13.295(6) ?, b = 5.659(2) ?, c = 16.144(8) ?, β = 109.73(5)°, V = 1143.3(9) ?³, and Z = 4. Two crystalline forms (II and III) reported herein, are polymorphs of the reported monoclinic form (I). Form II exists in the orthorhombic system, space group Pca2₁, with unit cell constants a = 11.631 (2) ?, b = 13.163 (3) ?, c = 7.3977 (14) ?, V = 1132.6 (4) ?³, and Z = 4. Form III also crystallizes in the orthorhombic system, however in space group Pbca, with unit cell parameters a = 11.8100(8) ?, b = 7.4075(5) ?, c = 25.8729(19) ?, V = 2263.4(3) ?³, and Z = 8. Variations in the hydrogen bonding connectivity help to distinguish these two forms from the monoclinic, whereas crystal packing differentiates the two orthorhombic forms. The conformation of the C=C (C2–C3) is E for both orthorhombic forms.     

The Structure of the Antioxidant 2,3,4-Trihydroxybenzoic Acid Dihydrate

Abstract  

The structure of 2,3,4-trihydroxybenzoic acid dihydrate has been determined at 120 K from a twinned crystal. The compound crystallizes in the centrosymmetric space group \textP[`1] \text{P}\bar{1} with Z = 2 and unit cell parameters a = 6.6165(14), b = 7.2341(14), c = 9.716(2) Å, α = 75.632(16), β = 76.818(17), γ = 77.520(16)°. There is extensive hydrogen bonding within the structure and evidence for intermolecular π–π interactions between parallel aromatic rings. The compound does not display the familiar carboxylic acid hydrogen-bonded dimer found in many similar compounds. The 2,3,4-trihydroxybenzoic acid molecules are however arranged in a head-to-tail chain and linked through two water molecules in an unusual intermolecular hydrogen bonding motif.     

Histamine Molecule and Dianion Oxalate are Efficient Blocks for Building 2D Supramolecular Networks

Abstract  

One salt and two Cu(II) complexes (H₂hsm)(ox), 1, [Cu(hsm)(ox)], 2, and [Cu(hsm)(ox)H₂O], 3, have been synthesized and X-ray characterized (hsm is histamine and ox²⁻ is the oxalate dianion). Starting from the prochiral tetracoordinated complex 2, pentacoordinated complex 3 crystallizes as a racemic mixture of the enantiomeric Δ and Λ isomers, in space group P2₁/c. In all cases, the side chain of the hsm group is gauche, allowing the formation of strong hydrogen bonds in the salt 1, and to chelate the metal center in complexes 2 and 3. The combination hsm/ox seems to favor the formation of 2D supramolecular structures (planes or wavy planes), through efficient networks of N–H···O hydrogen bonds. Cell parameters: 1, P2₁/c, a = 6.260 (2) ?, b = 11.500 (4) ?, c = 12.525 (4) ?, β = 104.047 (17)o; 2, C2/c, a = 10.7966 (13) ?, b = 15.5622 (16) ?, c = 11.3996 (15) ?, β = 106.261 (11)o; 3, P2₁/c, a = 7.0627 (6) ?, b = 7.1323 (6) ?, c = 20.0296 (19) ?, β = 91.529 (7)o.