Network hydrogen bonding: the crystal and molecular structure of cubane-1,3,5,7-tetracarboxylic acid dihydrate

The structure of cubane-1,3,5,7-tetracarboxylic acid dihydrate (1) has been determined. It crystallizes in the space groupP2₁/c with cell dimensionsa=6.503(1),b=19.173(1),c=10.527(1) Å, β=101.60(1). The details of this structure have reaffirmed the fact that the cubane skeleton is a flexible entity which reflects its steric and electronic environment. Of the four carboxylic acid groups three adopt asyn conformation while the fourth adopts ananti conformation. The orientation of these groups with respect to the cubane skeleton is reflected in the C?C bond lengths. Those C?C bonds which are perpendicular to the carboxylic acid groups are the longest and those which are most nearly eclipsed are the shortest in the cubane skeleton. In all cases it is the C=O rather than the C?O bond which is most nearly eclipsed with a C?C bond. The tetrahedral orientation of the substitutents does not express itself in a three dimensional supramolecular assembly; however, all four carboxylic acid groups are involved in very strong donor hydrogen bonds which result in a two dimensional array parallel to (100). An additional surprising results is the fact that none of the four substituents participate in traditional hydrogen bonded carboxylic acid dimeric moieties.     

Intra- vs intermolecular hydrogen bonding. The crystal structure of 5-methyl-2-hydroxyacetophenone thiosemicarbazone monohydrate and salicylaldehyde-2-methylthiosemicarbazone monohydrate

The crystal structure of 5-methyl-acetophenonethiosemicarbazone monohydrate,A, and salicylaldehyde-2-methylthiosemicarbazone monohydrate,B, were determined using single crystal X-ray diffraction.A crystallizes in the monoclinic space groupC2/c, with lattice parametersa=14.161(2),b=15.753(1) ?,c=11.084(1) ?, β=112.59(1)° andZ=4, yielding a calculated density ofD _calc=1.352 mg/m³.B crystallizes in the triclinic space groupP1, witha=7.233(2) ?,b=7.371(2) ?,c=11.841(2) ?, α=82.77(2)°, β=78.33(2)°, γ=63.06(2)° andD _calc=1.371 mg/m³ forZ=2,. In bothA andB the immine nitrogen and the sulfur atom areanti with respect to N2-C8. WhileA presents the usual intramolecular six membered hydrogen bond ring,B has instead an intermolecular hydrogen bond between the hydroxy moiety of the salicyladehyde and a water molecule. AM1 calculations agree with the experimental conformations observed in both compounds. Contribution No. 1619 of the Instituto de Química, UNAM.     

Hydrogen bonding patterns in bis(pyrimethamine hydrogen sulfate) monohydrate

The crystal structure of the compound bis [2,4-diamino-5-(p-chlorophenyl)-6-ethyl pyrimidinium hydrogen sulfate] monohydrate was studied by X-ray diffraction methods. The compound crystallises in orthorhombic system, space group P2₁2₁2₁, a=18.531(2) ?, b=16.190(2) ?, c=10.777(2) ?, V=3233.3(8), Z=4. The asymmetric unit shows the presence of two crystallographically independent pyrimethamine molecules, two hydrogen sulfate anions, and a water molecule. The hydrogen sulfate anions form a cyclic hydrogen bonded motif R₂ ²(8) with the 2-amino pyrimidine of the respective protonated pyrimethamine cations, through N–H···O hydrogen bonds. Thus the sulfate anions mimic the role of carboxylate anions observed in many aminopyrimidine-carboxylate interactions. This motif self assembles through DDAA array of quadruple hydrogen bonds, N–H···Cl, O–H···O and C–H···O hydrogen bonds.Supplementary material CCDC-293607 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge at www.ccdc.cam.ac.uk/conts/retrieving.html [or from the Cambridge Crystallographic Data Centre (CCDC), 12 Union Road, Cambridge CB2 IEZ, UK; fax: C44 (0) 1223-336033; e-mail: deposit@ccdc.cam.ac.uk].     

The hydrogen bonding in 1-ethynyl-2-(2′-carbethoxy-1′-vinyl)-2,3-dimethyl-6-isopropyl-cyclohexan-1-ol

The X-ray crystal structure of the title compound, C₁₈H₂₈O₃, is determined. The hydrogen bond scheme does not follow considerations based on hierarchies of donor and acceptor strengths. The hydroxyl group of the molecule accepts only very weak C–H···O interactions.     

Crystal and molecular structure of 2,7-di-tert-butyl-9,9-dimethyl-4,5-xanthenedicarboxylic acid

The crystal and molecular structure of molecular cleft 2,7-di-tert-butyl-9,9-dimethyl-4,5-xanthenedicarboxylic acid (1) is reported. Crystal data for 1: triclinic, space group P, a = 7.934(2), b = 10.387(2), c = 14.084(3) Å, = 96.049(3), = 101.231(4), = 95.635(4)°, V = 1123.7(4) ų, and D _c = 1.21 g/cm³, for Z = 2. The molecule crystallizes as a cyclic, hydrogen-bonded dimer held together by four O–H······O hydrogen bonds involving four carboxyl groups each of which interact by way of a cyclic hydrogen-bonded motif. The complex organizes in the solid state to form a 2D layered structure.     

Network hydrogen bonding in two new cocrystals sustained by 731-1731-1731-1, a tetrahedral hydrogen bond donor

We report details of the synthesis and X-ray crystal structures of two new cocrystals that are sustained by the tetrahedral hydrogen bond donor [Mn(CO)₃(₃-OH)]₄. [Mn(CO)₃(₃-OH)]₄· 2(2,3,5,6-tetramethylpyrazine)·2H₂O·2MeCN,a=21.503(3),b=12.674(1),c=17.318(2), =102.15(2), C2/c,D _calc=1.46 mg/m³,Z=4,4188 observed reflns,R _f=0.047,R _w=0.040; 1.[Mn(CO)₃(₃-OH)]₄·4,4-dipyridyl·2MeCn,a=16.942(6),b=12.395(2),c=18.790(6), =114.88(3), C 2/c,D _calc=1.60 mg/m³,Z=4,2430 observed reflns,R _f=0.043,R _w=0.051;2. 1 crystallizes as a 2-D grid, whereas2 forms 1-D strands. The hydrogen bond patterns exhibited by1 and2 are analyzed in the context of our earlier studies involving [Mn(CO)₃(₃-OH)]₄ and other relevant literature.     

Structure determination and hydrogen bonding of 1-naphthoxyacetic acid, a potential plant growth hormone

1-Napthoxyacetic acid crystallizes in the centrosymmetric space group C2/c (No. 15) with cell dimensions of a=14.273(2)Å, b=5.845(1)Å, c=24.211(1)Å, =105.815(2)°. The structure of the title compound reveals a carboxyl group-naphthalene ring dihedral angle of 4.85(14)°, O—H- - -O hydrogen bonded dimer, hydrogen bond distance of 2.640(2)Å, hydrogen bond angle of 172(2)°, and a cis configuration of O2 (double bond) and O3 relative to the C11—C12 bond all of which indicate that the title compound may be effective as a plant growth hormone.     

Liquid crystalline G phase of self assembled donor-acceptor molecules by intermolecular hydrogen bonding

The interaction with donor p-n-alkylbenzoic acid and acceptor nonyl-p-hydroxy benzoate molecules was studied. The likely association of these molecules to complexes is studied by intermolecular hydrogen bonding. The textures are observed by polarizing optical microscope with corresponding transitions confirmed by differential scanning calorimetry. The molecular complexes exhibited enantiotropic crystal G phases in both heating and cooling cycles. The relevant functional groups C═O, C-O and OH in formation of molecular complexes are attributed with spectral shifts in infrared spectra and further with absorption studies. The proton NMR studies convinced the structural aspects of hydrogen bonded structure. Crystal parameters were studied with powdered X-ray diffraction. The results show that constituent molecules self organize through intermolecular hydrogen bonding in the formation of crystal G phase.     

The crystal structure of a bis(2,6-pyridinedicarboxylato)chromate(III) anion with an elaborate network of hydrogen bonding and π stacking

The synthesis, X-ray crystallography, spectroscopic, and electrochemical properties of the title compound, [Hdpa][Cr(dipic)₂]·3H₂O, 1, are reported. Compound 1 crystallized in the triclinic space group P-1 with a = 7.1057(11) ?, b = 12.965(2) ?, c = 14.269(2) ?, α = 80.306(3)°, β = 82.101(2)°, γ = 83.799(2)°, and V = 1278.6(4) ?³ with Z = 2. The distorted octahedral chromium anions are part of an elaborate network of hydrogen bonding formed by the waters of solvation, the anion, and cation as well as π-stacking interactions.     

Structural characterization of oxidized lumiflavin hydrochloride hydrate: Comparison with the hydrogen bonding at the cofactor of flavoproteins

In order to examine the possibility of hydrogen bonding around the flavin ring, an X-ray diffraction study of the title compound was undertaken. Crystals of lumiflavin hydrochloride hydrate [2(C₁₃H₁₂N₄O₂) 4 HCl 7 H₂O] are triclinic, space group ,Z=2,a=11.064(1),b=17.903(1),c=9.891(1)Å, =111.9(6), -96.4(8), =91.6(7)°. We present the crystal structure of this compound and compare it with other flavin derivatives and with the structure of the active site of some flavoproteins.     

Hydrogen bonding in proton-transfer compounds of 5-sulfosalicylic acid with ortho-substituted monocyclic heteroaromatic Lewis bases

The crystal structures of the 1:1 proton-transfer compounds of 5-sulfosalicylic acid with the ortho-substituted monocyclic heteroaromatic Lewis bases, 2-aminopyridine, 2-hydroxypyridine and 2-aminopyrimidine, viz. 2-aminopyridinium 5-sulfosalicylate (1), 2-hydroxypyridinium 5-sulfosalicylate monohydrate (2) and 2-aminopyrimidinium 5-sulfosalicylate monohydrate (3) have been determined and their hydrogen-bonding patterns described. All compounds are monoclinic, space group P2₁/c, with Z=4 in cells with dimensions a=7.898(5), b=11.159(11), c=14.912(7) ?, β=96.849(11)° (1);=7.260(2), b=15.292(3), c=12.615(2) ?, β=102.45(5)° (2) and a=7.0430(7), b=12.1871(16), c=16.2825(12) ?, β=101.364(7)° (3). All three compounds show some molecular disorder, in 1 within the cation species and with both 2 and 3, a similar rotational disorder in the anion sulfonate group. Hydrogen bonding in all three compounds together with significant cation-anion or cation-cation inter-ring π–π interactions generate three-dimensional layered polymer structures.     

Hydrogen bonding in labdane diterpenoids, labda-7,12(E),14-triene-17-oic acid and labda-12(Z),14,17-triene-18-oic acid

Two labdane diterpenoids, labda-7,12(E),14-triene-17-oic acid (1) and labda-12(Z),14,17-triene-18-oic acid (2), C₂₀H₃₀O₂, have been isolated from Croton oblongifolius. Both 1 and 2 crystallized in the monoclinic system, space group C2, with cell dimensions of a = 21.912(1) Å, b = 7.4002(4) Å, c = 11.5079(7) Å, = 101.999(1)^o and a = 21.308(2) Å, b = 11.9067(9) Å, c = 7.5606(6) Å, = 100.763(1)^o, respectively. Compound 1, a rare example of carboxylic group bound to a cyclohexene ring, forms an infinite intermolecular hydrogen-bonded polymer [O1 O2(–x + 1/2, y + 1/2, –z + 2) 2.697(2) Å], whereas molecules of compound 2 are linked to form an asymmetric hydrogen-bonded dimer [O1 O2(–x, y, –z) 2.657(3) Å].     

Crystal structure and hydrogen bonding of propargylammonium hexafluorosilicate, 2(C3H6N)+ (SiF6)2?

The X-ray crystal structure of propargylammonium hexafluorosilicate, 2(C₃H₆N)⁺ (SiF₆)²⁻, is determined. The SiF₆ anion is involved in N−H...F and C−H...F interactions with eight surrounding cations. This involves two-three-and four-center N−H...F hydrogen bonds, and additional C−H...F interactions with C...F distances down to 2.963(6) ?. The alkynyl C−H donors form only C−H...F interactions of unfavorable geometries.     

Influence of flexible chain,polar substitution and hydrogen bonding on phase stability in Shiff based (4)PyBD(4I)BrA-nOBA series of liquid crystals

Shiff based Linear Hydrogen Bonded Liquid Crystalline homologues, viz., (4)PyBD(4^I)BrA-nOBAs for n = 2,3,4,5,6,7,8,10,11 and 12 are synthesized. ¹H-NMR and ¹³C-NMR studies confirm the formation of HBLC and IR confirms the linear hydrogen bonding. Liquid crystal phase abundance, transition temperatures, enthalpy and order of transition are investigated by Polarized Optical Microscopy textural studies and Differential Scanning Calorimetry. Nematic, Smectic-A, -D, -C, B_hexatic, -B_Crystal, -F, -I and –G phases are identified. Large LC phase variances, viz., NAB_hexFG and NACFG are exhibited by intermediate chain length with n = 5 and 6. A-C transition exhibited unique II-order nature. II-order nature for G-Solid transition explained. Phase diagram drawn with flexible chain length infers INA, and ACF and CIF MultiCritical Points and Lifshitz behaviour. NA TriCiritical Point predicted in [3+7] binary. Influences of chain length, linear HB and end polar(-Br) substitution for LC phase stability are is discussed. Results of Phase stability are discussed in the wake of the body of the data and reports in other LCs. DSC enthalpy suggests for utility of intermediate and higher homologues for device savvy tilted Smectic LC phases.     

The hydrogen bonding in 2-amino-3-cyano-4-(3-nitrophenyl)-4,6-dihydro-5H-pyrano[3,2-c]quinolin-5-one N,N-dimethylformamide solvate monohydrate

The crystal structure of 2-amino-3-cyano-4,6-dihydro-4-(3-nitrophenyl)-5H-pyrano[3,2-c]quinolin-5-one N,N-dimethylformamide solvate monohydrate is determined by room temperature X-ray diffraction. The title compound 1, C₂₂H₂₁N₅O₆, is triclinic, space group P-1, a=9.109(2) ?, b=11.340(2) ?, c=12.485(2) ?, α=70.02(1)°, β=69.36(1)°, γ=67.32(1)°, Z=2, V=1081.4(4) ?³. It is interesting that a bridge-like hydrogen bond O–H···O is formed between the title compound and solvent molecules of water with molecular ratio of 2:2 building a bi-layer framework. In addition, there are two other types of classical hydrogen bonds N–H···N and N–H···O in the crystal structure.Supplementary material Crystallographic data for the structure reported in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication no. CCDC-275001. Copies of available material can be obtained, free of charge, on application to the Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK, (fax: +44-(0) 1223–336033 or e-mail: deposit@ccdc.cam.ac.uk).     

Synthesis of liquid crystals based on hydrogen-bonding of 4-(Octyloxy)benzoic acid with 4-alkylbenzoic acids

A molecular recognition process has been used to form new mesogenic molecular structures, where intermolecular hydrogen bonding occurs between 4-(octyloxy)benzoic acid (8BAO) and four 4-alkylbenzoic acids (nBAs, n = 2, 5, 6, 7). The synthesis of these complexes has been attained by resorting to mechanochemistry. The resulting materials have been characterized by polarizing optical thermal microscopy, differential scanning calorimetry, vibrational spectroscopy, X-ray powder diffraction, and ¹H NMR relaxometry. All the elements of the series show the formation of a mesophase. For one of the complexes, its electro-optical properties have also been assessed, resulting comparable to those of other widely used liquid crystals.     

Strychnine-8-ammonio-2-naphthalenesulfonate-water (1/1/3.5): The first structure of a strychnine or brucine compound with a zwitterionic species

The crystal structure of the 1:1 adduct hydrate of strychnine with 1,7-Cleve's acid (8-amino-2-naphthalenesulfonic acid), namely strychnine-8-ammonio-2-naphthalenesulfonate-water (1/1/3.5) has been determined and provides a unique example of a neutral association involving strychnine and an achiral zwitterionic acid species, previously unobserved in the structures of either strychnine or brucine addition compounds. Crystals are orthorhombic, space group P2₁2₁2₁, with Z=4 in a cell with dimensions a=10.4484(8), b=30.850(3), c=9.4998(11) ?. Hydrogen bonding involving all available proton-donor and acceptor sites on all species gives rise to a three-dimensional framework polymer structure. The crystallographic literature for strychnine and brucine and their compounds is also reviewed.     

N‐H⋅⋅⋅O,O‐H⋅⋅⋅O hydrogen bonded supramolecular formation in the cocrystal of salicylic acid with N‐containing bases

Cocrystals of salicylic acid (derived from reaction between aspirin and coformers) with 4,4′dipyridyl, nicotinamide, isonicotinamide, N,N′‐diacetylpiperazine and piperazine have been examined with intent to improve physicochemical properties of antipyretic agent. All of the resulting cocrystals, salicylic acid/4,4′dipyridyl (2:1), salicylic acid/nicotinamide (1:1), salicylic acid/isonicotinamide (1:1), salicylic acid/piperazine (1:0.5) and salicylic acid/ N,N′‐diacetylpiperazine (2:1) (derived from reaction between aspirin and piperazine) are obtained solution cooling/evaporation experiments. The structural analysis has shown that the well‐known COOH ⋅⋅⋅ N heterosynthon was considered the key element in the cocrystals design strategy. The carboxylic acid ⋅⋅⋅ pyridine hydrogen bond is an often used supramolecular synthon. The results from X‐ray Powder Diffraction, DSC, Raman and single‐crystal X‐ray analysis revealed the formation of cocrystal of salicylic acid with several coformers.     

Low temperature powder diffraction and DFT solid state computational study of hydrogen bonding in NH4VO3

The crystal structure of NH₄VO₃ was refined by the geometry optimization done by total energy minimization in solid state using DFT/plane waves approach. The lattice parameters were derived by the Le Bail technique from the low temperature X‐ray (40‐293 K) and synchrotron (100‐293 K) powder diffraction data. The structure is formed by the infinite chains of irregular VO₄ tetrahedra running approximately parallel to the c‐axis, which are interlinked by the ammonium ions placed between them. The ammonium ions link to the [VO₄]_∞ chains through one linear, one bifurcated and two trifurcated N‐H…O hydrogen bonds. Considering their stability there are six distinct N‐H…O hydrogen bonds: two strong with the N‐H…O bond angles close to the straight, two medium with the bond angles of 123° and 148° and two very bent (105° and 107°) and hence weak hydrogen bonds. There is a reasonable agreement between the energies of the stretching ν(NH) modes estimated using the optimised N…O contact distances and those obtained experimentally. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Studies of homogeneous-nucleation-based crystal growth: significant role of phenyl ring in the structure formation

Low-temperature crystal growth was investigated in the fragile liquids of iso-propylbenzene, dimethylphthalate, diphenylphthalate, and 2-methyltetrahydrofuran by using an optical microscope. Homogeneous-nucleation-based (HNB) crystal growth was observed to proceed in the supercooled liquids of the former three substances around and below their glass-transition temperatures, as in the cases of o-terphenyl, toluene, and other fragile liquids, but not detected in 2-methyltetrahydrofuran. Thus far, the growth has been observed only for the substances possessing phenyl group(s) in the molecule. The maximum rates of the growth were found to decrease with increasing the size of substituents to the phenyl ring(s). It was concluded from this fact that the C-H?π(electron) intermolecular interaction between phenyl rings enhances to generate an ordered region required for the crystal nucleation and thereby the HNB crystal growth. Among all the observations of the HNB growth, a rough relation was found that the maximum growth rate increases with an increasing maximum-rate temperature normalized by the respective glass transition temperatures.