Two-dimensional Hydrogen-bonded Network Research Articles

Effect of high pressure on the typical 2D hydrogen-bonded crystal azodicarbonamide

We have performed in situ Raman scattering and synchrotron angle-dispersive X-ray diffraction (ADXRD) investigations to explore high-pressure behaviors of azodicarbonamide (C2N4O2H4, ADC) to 21.6 and 23.8 GPa, respectively. ADC exhibits the representative two-dimensional (2D) hydrogen-bonded networks, and is the most hugely used foaming agent in industry both under ambient and high pressures. Careful identification of external modes and indexation of Bragg diffraction peaks under different pressures demonstrate ADC crystal remains the P21/c symmetry in this study. The bulk modulus (B0) and its pressure derivative (B0’) are determined to be 13.2(7) GPa and 8.2(2) by fitting the isothermal third Vinet equation of state (EOS). The conformation change of ADC molecule has been observed at 12.7 GPa. And this is evidenced by the splitting of skeleton atoms vibrations and the discontinuous evolutions with respect to hydrogen bond donor (NH) vibrations. First principle calculation reveals the observed confirmation change arises from the discontinuous variation of the torsion angel between H2NC=O and CN=NC skeleton groups. Hirshfeld surface analysis indicates that the extensive hydrogen bonds within 2D networks dominate the intermolecular close contacts even under high pressures. The intermolecular interaction energy calculation also implies that the energy between neighboring molecules in the 2D layer dominates the networks stability, whereas the energy between neighboring molecules in the second nearest adjacent layer is the primary factor for crystal instability. The cooperativity of the molecular flexibility and directional hydrogen bonds is responsible for structural stability under high pressures.

Crystal structure, vibrational and optic properties of 2-N-methylamino-3-methylpyridine N-oxide – Its X-ray and spectroscopic studies as well as DFT quantum chemical calculations

The crystal and molecular structure and physicochemical properties of 2-N-methylamino-3-methylpyridine N-oxide (MA3MPO) have been studied. MA3MPO was synthesized from 2-amino-3-methylpyridine by several steps to form colorless crystals suitable for crystallographic analysis. The data reveal that MA3MPO crystallizes in the monoclinic space group P21/n. The studied compound contains a nearly flat triply substituted pyridine skeleton whose structure is stabilized by an intramolecular N–H⋅⋅⋅O hydrogen bond. The N-oxide molecules are connected together by weak C–H⋯O hydrogen bonds, an acceptor of which is the oxygen atom from the N-oxide group. This leads to creation of two-dimensional network of hydrogen bonds. Its IR, Raman, UV–Vis and luminescence spectra have been measured and analyzed on the basis of DFT and NBO quantum chemical calculations in which the B3LYP/6-311++G(d,p) approach was applied. The distribution of the electron levels in the studied compound has been analyzed in terms of the possibility of its participation in the ligand-to-lanthanide ion energy transfer.

Stepwise Synthesis, Hydrogen-Bonded Supramolecular Structure, and Magnetic Property of a Co–Mn Heterodinuclear Complex

A cobalt(III)–manganese(II) heterometallic dinuclear complex, [MnII{CoIII(µ-Himn)3}Cl2(CH3OH)], was prepared by a metalloligand approach. X-ray crystallographic analysis indicated that the metalloligand [CoIII(Himn)3] underwent mer/fac geometrical isomerization upon coordination to a Mn ion. Owing to the non-coordinating N–H bonds in the [CoIII(Himn)3] moiety, the heterodinuclear complex exhibited hydrogen bond interactions with the Cl− ligand of the neighboring complex to construct two-dimensional hydrogen-bond networks. The bond distances around the Mn center and the χMT value at 300 K indicate that the Mn center is in a divalent state. The temperature dependence of the χMT product and field dependence of the magnetization showed the isotropic nature of the MnII center.

Unraveling Anhydrous Proton Conduction in Hydroxygraphane.

We predict that graphane functionalized with hydroxyl groups, hydroxygraphane, can conduct protons in the complete absence of water, as shown from density functional theory calculations. Hydroxygraphane's anhydrous intrinsic proton conductivity results from the self-assembling two-dimensional network of hydrogen bonds on its surface. We show that the proton conduction occurs through a Grotthuss-like mechanism, as protons hop between neighboring hydroxyl groups, aided by their rotation. Our calculations predict that hydroxygraphane has a direct bandgap of 3.43 eV, a phonon dispersion spectrum with no instabilities, and a 2-D Young's modulus and Poisson's ratio stiffer than those for graphane-the parent material for hydroxygraphane. Hence, hydroxygraphane has the desired electronic and mechanical properties to make it a viable candidate for a proton exchange membrane material capable of operating under anhydrous or low-humidity conditions.

The crystal structures of benzyl-ammonium phenyl-acetate and its hydrate.

The title compounds benzyl-ammonium phenyl-acetate, C7H10N+·C8H7O2 - (1), and its monohydrate, C7H10N+·C8H7O2 -·H2O (2), can be obtained by evaporating methano-lic solutions containing equimolar amounts of benzyl-amine and phenyl-acetic acid in the absence and presence of water, respectively. N-H⋯O hydrogen bonds in the crystal structure of 1 lead to the formation of hydro-philic channels running along the b-axis direction. The hydrogen-bonding system is best described by fused R 3 4(10) ring patterns, often observed in ammonium carboxyl-ate salts. In 2, the presence of the crystal water leads to the formation of a two-dimensional hydrogen-bonding network. The benzyl moieties in 1 and 2 form hydro-phobic layers in the crystal structures with the aromatic rings adopting edge-to-face arrangements.

Structures of the hydrate and dihydrate forms of the DNA-binding radioprotector methyl-pro-amine.

Methyl pro-amine {N,N,3-trimethyl-4-[6-(4-methyl-piperazin-1-yl)-1H,3'H-[2,5'-bibenzo[d]imidazol]-2'-yl]aniline}, C28H35N7O2, crystallized as both a dihydrate, C28H31N7·2H2O, and monohydrate, C28H31N7·H2O, form from water in the presence of β-cyclo-dextrin, in the P21/c and P21/n space groups, respectively. The two structures adopt different conformations and tautomeric forms as a result of the differing crystal packing as dictated by hydrogen-bonding inter-actions. The dihydrate crystallizes as a three-dimensional hydrogen-bonded network, while the monohydrate crystallizes as a two-dimensional hydrogen-bonded network.

Controllable Density of Atomic Bromine in a Two-Dimensional Hydrogen Bond Network

Using atomic bromine (Br) and pentacene molecules, we successfully constructed and characterized a large-scale Br atom-mediated two-dimensional (2D) organic network on a Ag(111) surface by combining molecular beam epitaxy with scanning tunneling microscopy. The Br atoms form −C–H···Br hydrogen bonds with pentacene molecules in the network, and the number of Br atoms among pentacene molecules can be tuned from one to five by increasing the pressure or exposure time of hydrogen bromide (HBr) gas. In addition, all of the Br atoms of five 2D organic networks fill themselves in the position of maximum number of hydrogen bonds.

Fast Rotational Diffusion of Water Molecules in a 2D Hydrogen Bond Network at Cryogenic Temperatures.

Individual water molecules or small clusters of water molecules contained within microporous minerals present an extreme case of confinement where the local structure of hydrogen bond networks are dramatically altered from bulk water. In the zinc silicate hemimorphite, the water molecules form a two-dimensional hydrogen bond network with hydroxyl groups in the crystal framework. Here, we present a combined experimental and theoretical study of the structure and dynamics of water molecules within this network. The water molecules undergo a continuous phase transition in their orientational configuration analogous to a two-dimensional Ising model. The incoherent dynamic structure factor reveals two thermally activated relaxation processes, one on a subpicosecond timescale and another on a 10-100ps timescale, between 70 and 130K. The slow process is an in-plane reorientation of the water molecule involving the breaking of hydrogen bonds with a framework that, despite the low temperatures involved, is analogous to rotational diffusion of water molecules in the bulk liquid. The fast process is a localized motion of the water molecule with no apparent analogs among known bulk or confined phases of water.

Crystal structure of methylprednisolone acetate form II, C24H32O6

The crystal structure of methylprednisolone acetate form II, C24H32O6, has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional techniques. Methylprednisolone acetate crystallizes in space group P212121 (#19) with a = 8.17608(2), b = 9.67944(3), c = 26.35176(6) Å, V = 2085.474(6) Å3, and Z = 4. Both hydroxyl groups act as hydrogen bond donors, resulting in a two-dimensional hydrogen bond network in the ab plane. C–H⋯O hydrogen bonds also contribute to the crystal energy. The powder pattern is included in the Powder Diffraction File™ as entry 00-065-1412.

Sulfur as hydrogen-bond acceptor in cocrystals of 2-thio-modified thymine.

Doubly and triply hydrogen-bonded supramolecular synthons are of particular interest for the rational design of crystal and cocrystal structures in crystal engineering since they show a high robustness due to their high stability and good reliability. The compound 5-methyl-2-thiouracil (2-thiothymine) contains an ADA hydrogen-bonding site (A = acceptor and D = donor) if the S atom is considered as an acceptor. We report herein the results of cocrystallization experiments with the coformers 2,4-diaminopyrimidine, 2,4-diamino-6-phenyl-1,3,5-triazine, 6-amino-3H-isocytosine and melamine, which contain complementary DAD hydrogen-bonding sites and, therefore, should be capable of forming a mixed ADA-DAD N-H...S/N-H...N/N-H...O synthon (denoted synthon 3sN·S;N·N;N·O), consisting of three different hydrogen bonds with 5-methyl-2-thiouracil. The experiments yielded one cocrystal and five solvated cocrystals, namely 5-methyl-2-thiouracil-2,4-diaminopyrimidine (1/2), C5H6N2OS·2C4H6N4, (I), 5-methyl-2-thiouracil-2,4-diaminopyrimidine-N,N-dimethylformamide (2/2/1), 2C5H6N2OS·2C4H6N4·C3H7NO, (II), 5-methyl-2-thiouracil-2,4-diamino-6-phenyl-1,3,5-triazine-N,N-dimethylformamide (2/2/1), 2C5H6N2OS·2C9H9N5·C3H7NO, (III), 5-methyl-2-thiouracil-6-amino-3H-isocytosine-N,N-dimethylformamide (2/2/1), (IV), 2C5H6N2OS·2C4H6N4O·C3H7NO, (IV), 5-methyl-2-thiouracil-6-amino-3H-isocytosine-N,N-dimethylacetamide (2/2/1), 2C5H6N2OS·2C4H6N4O·C4H9NO, (V), and 5-methyl-2-thiouracil-melamine (3/2), 3C5H6N2OS·2C3H6N6, (VI). Synthon 3sN·S;N·N;N·O was formed in three structures in which two-dimensional hydrogen-bonded networks are observed, while doubly hydrogen-bonded interactions were formed instead in the remaining three cocrystals whereby three-dimensional networks are preferred. As desired, the S atoms are involved in hydrogen-bonding interactions in all six structures, thus illustrating the ability of sulfur to act as a hydrogen-bond acceptor and, therefore, its value for application in crystal engineering.

Copper(II) bis(4,4,4-trifluoro-1-phenylbutane-1,3-dionate) complexes with pyridin-2-one, 3-hydroxypyridine and 3-hydroxypyridin-2-one ligands: molecular structures and hydrogen-bonded networks.

Copper(II) bis(4,4,4-trifluoro-1-phenylbutane-1,3-dionate) complexes with pyridin-2-one (pyon), 3-hydroxypyridine (hpy) and 3-hydroxypyridin-2-one (hpyon) were prepared and the solid-state structures of (pyridin-2-one-κO)bis(4,4,4-trifluoro-3-oxo-1-phenylbutan-1-olato-κ2O,O')copper(II), [Cu(C10H6F3O2)2(C5H5NO)] or [Cu(tfpb-κ2O,O')2(pyon-κO)], (I), bis(pyridin-3-ol-κO)bis(4,4,4-trifluoro-3-oxo-1-phenylbutan-1-olato-κ2O,O')copper(II), [Cu(C10H6F3O2)2(C5H5NO)2] or [Cu(tfpb-κ2O,O')2(hpy-κO)2], (II), and bis(3-hydroxypyridin-2-one-κO)bis(4,4,4-trifluoro-3-oxo-1-phenylbutan-1-olato-κ2O,O')copper(II), [Cu(C10H6F3O2)2(C5H5NO2)2] or [Cu(tfpb-κ2O,O')2(hpyon-κO)2], (III), were determined by single-crystal X-ray analysis. The coordination of the metal centre is square pyramidal and displays a rare example of a mutual cis arrangement of the β-diketonate ligands in (I) and a trans-octahedral arrangement in (II) and (III). Complex (II) presents the first crystallographic evidence of κO-monodentate hpy ligation to the transition metal enabling the pyridine N atom to participate in a two-dimensional hydrogen-bonded network through O-H...N interactions, forming a graph-set motif R22(7) through a C-H...O interaction. Complex (III) presents the first crystallographic evidence of monodentate coordination of the neutral hpyon ligand to a metal centre and a two-dimensional hydrogen-bonded network is formed through N-H...O interactions facilitated by C-H...O interactions, forming the graph-set motifs R22(8) and R22(7).

Isomorphous rare-earth bis[bis(2,6-diisopropylphenyl)phosphate] complexes and their self-assembly into two-dimensional frameworks by intramolecular hydrogen bonds.

The crystal structures of rare-earth diaryl- or dialkylphosphate derivatives are poorly explored. Crystals of bis[bis(2,6-diisopropylphenyl)phosphato-κO]chloridotetrakis(methanol-κO)neodymium methanol disolvate, [Nd(C24H34O4P)Cl(CH4O)4]·2CH3OH, (1), and of the lutetium, [Lu(C24H34O4P)Cl(CH4O)4]·2CH3OH, (2), and yttrium, [Y(C24H34O4P)Cl(CH4O)4]·2CH3OH, (3), analogues have been obtained by reactions between lithium bis(2,6-diisopropylphenyl)phosphate and LnCl3(H2O)6 (in a 2:1 ratio) in methanol. Compounds (1)-(3) crystallize in the C2/c space group. Their crystal structures are isomorphous. The molecule possesses C2 symmetry with a twofold crystallographic axis passing through the Ln and Cl atoms. The bis(2,6-diisopropylphenyl)phosphate ligands all display a κ1O-monodentate coordination mode. The coordination polyhedron for the metal atom [coordination number (CN) = 7] is a distorted pentagonal bipyramid. Each [Ln{O2P(O-2,6-iPr2C6H3)2}2Cl(CH3OH)4] molecular unit exhibits two intramolecular O-H...O hydrogen bonds, forming six-membered rings, and two intramolecular O-H...Cl interactions, forming four-membered rings. Intermolecular O-H...O hydrogen bonds connect each unit via four noncoordinating methanol molecules with four other units, forming a two-dimensional hydrogen-bond network. Crystals of bis[bis(2,6-diisopropylphenyl)phosphato-κO]tetrakis(methanol-κO)(nitrato-κ2O,O')neodymium methanol disolvate, [Nd(C24H34O4P)(NO3)(CH4O)4]·2CH3OH, (4), have been obtained in an analogous manner from NdCl3(H2O)6. Compound (4) also crystalizes in the C2/c space group. Its crystal structure is similar to those of (1)-(3). The κ2O,O'-bidentate nitrate anion is disordered over a twofold axis, being located nearly on it. Half of the molecule is crystallographically unique (CNNd = 8). Unlike (1)-(3), complex (4) exhibits disorder of all three methanol molecules, one isopropyl group of the phosphate ligand and the NO3- ligand. The structure of (4) displays intra- and intermolecular O-H...O hydrogen bonds similar to those in (1)-(3). Compounds (1)-(4) represent the first reported mononuclear bis[bis(diaryl/dialkyl)phosphate] rare-earth complexes.

Face-to-Face Stacking and Saddle Distortion of 5,10,15,20-Tetra(4-hydroxyphenyl)porphyrinatocopper(II) in Two New Solvates

The crystal structures of the methanol nitrobenzene sesquisolvate hemihydrate (1) and the 3.75-dimethyl sulfoxide solvate monohydrate (2) of 5,10,15,20-tetra(4-hydroxyphenyl)porphyrinatocopper(II) (CuTOHPP) are reported. Both 1 and 2 crystallise in the triclinic system with two molecules of the metalloporphyrin in the asymmetric unit (Z′ = 2). Compound 1 exhibits an extended two-dimensional hydrogen-bonded network in the crystal, whereas discrete hydrogen-bonded assemblies of CuTOHPP and solvent molecules are found in 2. Face-to-face stacking of the metalloporphyrin units and O–H⋯O hydrogen bonding interactions are identified as the most important solid-state organisational features in both 1 and 2. Saddle distortion of the metalloporphyrin units is encountered in both new solvates and there are no Cu⋯O interactions, despite four hydroxy groups on each porphyrin ligand and the presence of oxygen donor solvent molecules. The methanol nitrobenzene sesquisolvate hemihydrate and the 3.75-dimethyl sulfoxide solvate monohydrate of 5,10,15,20-tetra(4-hydroxyphenyl)porphyrinatocopper(II) both crystallise in the triclinic system with two molecules in the asymmetric unit (Z′ = 2), featuring face-to-face stacking of the saddle-distorted metalloporphyrin units.

Crystal structures of N'-amino-pyridine-2-carboximidamide and N'-{[1-(pyridin-2-yl)ethyl-idene]amino}-pyridine-2-carboximidamide.

The crystal structures of N'-amino-pyridine-2-carboximidamide (C6H8N4), 1, and N'-{[1-(pyridin-2-yl)ethyl-idene]amino}-pyridine-2-carboximidamide (C13H13N5), 2, are described. The non-H atoms in compound 1 are nearly planar (r.m.s. deviation from planarity = 0.0108 Å), while 2 is twisted about the central N-N bond by 17.8 (2)°. Both mol-ecules are linked by inter-molecular N-H⋯N hydrogen-bonding inter-actions; 1 forms a two-dimensional hydrogen-bonding network and for 2 the network is a one-dimensional chain. The bond lengths of these mol-ecules are similar to those in other literature reports of azine and di-imine systems.

Reversible water uptake by a porous molecular crystal from metal complex of gemini surfactant

We present a novel porous molecular crystal (PMC) constructed using metal complexes, which shows a striking feature, namely that such a crystal exhibits a reversible transition in the crystal structure when subjected to water removal/uptake cycles. It was found that the dehydrated crystal adsorbed a given quantity of water, that is, each complex assembling block, derived from two gemini surfactant molecules with a bipyridyl spacer and two copper ions (Cu2+) coordinated, stuck to 10 molecules of water. Also, the water included in crystals might generate a unique two-dimensional (2D) hydrogen bond network, including metal–ligand complex units, counter ions and crystalline water. Specially, the crystalline structure was not destroyed upon desolvation, which is ascribed to the metal ion introduced as well as the counter ion (Br−) providing additional electrostatic interactions and hydrogen bonds. Our findings indicate that the introduction of metal ions may provide an alternative to the common weak interactions when designing PMCs. In addition, this crystal material is sensitive to moisture, extending the scope of such a gemini species for potential applications in chemical sensors and in humid environments.

Self-Assembly and External Modulation of a Flexible Porphyrin Derivative on Highly Oriented Pyrolytic Graphite.

With the aid of scanning tunneling microscopy, we have examined the two-dimensional hydrogen-bonded networks of carboxyl-functionalized porphyrin derivative H2TCPp molecules at the heptanoic acid/HOPG interface. Moreover, we have successfully modulated the self-assembly structure of H2TCPp by introducing 1,2-di(4-pyridyl)ethylene molecules into the assembled system. By performing density functional theory calculations, we also revealed the formation mechanisms of the different assemblies and the modulation process. Comparing the self-assembly structures at the liquid/solid interface with those in bulk crystals, we have obtained deep insight into the differences in H2TCPp assemblies between 2D and 3D networks. Furthermore, this research is expected to deepen our understanding of on-surface phenomena and to provide a feasible process toward 2D assembly regulation.

Significantly Dense Two-Dimensional Hydrogen-Bond Network in a Layered Zirconium Phosphate Leading to High Proton Conductivities in Both Water-Assisted Low-Temperature and Anhydrous Intermediate-Temperature Regions.

A highly stable layered zirconium phosphate, (NH4)2[ZrF2(HPO4)2] (ZrP-1), was synthesized by an ionothermal method and contains an extremely dense two-dimensional hydrogen-bond network that is thermally stable up to 573 K, leading to combined ultrahigh water-assisted proton conductivities of 1.45 × 10-2 S cm-1 at 363 K/95% relative humidity and sustainable anhydrous proton conductivity of 1.1 × 10-5 S cm-1 at 503 K.

Commensurate Superstructure of the {Cu(NO3)(H2O)}(HTae)(Bpy) Coordination Polymer: An Example of 2D Hydrogen-Bonding Networks as Magnetic Exchange Pathway.

The average and commensurate superstructures of the one-dimensional coordination polymer {Cu(NO3)(H2O)}(HTae)(Bpy) (H2Tae = 1,1,2,2-tetraacetylethane, Bpy = 4,4'-bipyridine) were determined by single-crystal X-ray diffraction, and the possible symmetry relations between the space group of the average structure and the superstructure were checked. The crystal structure consists in parallel and oblique {Cu(HTae)(Bpy)} zigzag metal-organic chains stacked along the [100] crystallographic direction. The origin of the fivefold c axis in the commensurate superstructure is ascribed to a commensurate modulation of the coordination environment of the copper atoms. The commensurately ordered nitrate groups and coordinated water molecules establish a two-dimensional hydrogen-bonding network. Moreover, the crystal structure shows a commensurate to incommensurate transition at room temperature. The release of the coordination water molecules destabilizes the crystal framework, and the compound shows an irreversible structure transformation above 100 °C. Despite the loss of crystallinity, the spectroscopic studies indicate that the main building blocks of the crystal framework are retained after the transformation. The hydrogen-bonding network not only plays a crucial role stabilizing the crystal structure but also is an important pathway for magnetic exchange transmission. In fact, the magnetic susceptibility curves indicate that after the loss of coordinated water molecules, and hence the collapse of the hydrogen-bonding network, the weak anti-ferromagnetic coupling observed in the initial compound is broken. The electron paramagnetic resonance spectra are the consequence of the average signals from Cu(II) with different orientations, indicating that the magnetic coupling is effective between them. In fact, X- and Q-band data are reflecting different situations; the X-band spectra show the characteristics of an exchange g-tensor, while the Q-band signals are coming from both the exchange and the molecular g-tensors.

Proton Hopping Mechanisms in a Protic Organic Ionic Plastic Crystal

We elucidate the dynamics and mechanism of proton transport in a protic organic ionic plastic crystal (POIPC) [TAZ][pfBu] by means of Born–Oppenheimer molecular dynamics simulations at 400 K and zero humidity. The arrangement of ionic species in the crystal offers a two-dimensional hydrogen bond network along which an acidic proton can travel from one cation to another through a sequence of molecular reorientations. The results suggest spontaneous autodissociation of the N–HN bond in the cation and multiple proton shuttle events from the cation’s nitrogen to the anion’s oxygen site in a native crystal. A complete proton transfer event is observed in simulations of a defective crystal with a single proton hole created in the cation. The barrier for proton transfer is determined using ab initio metadynamics simulations to be 7 kcal/mol, in agreement with experimental conductivity data. Using gas phase quantum chemical calculations, we propose [TAZ][CF3CF2CH2CF2SO3] as a compound that can show enhanced conductivity compared to that of [TAZ][pfBu].

Crystal structure of bis-(azido-κN)bis-(quinolin-8-amine-κ2N,N')iron(II).

The search for new mol-ecular materials with inter-esting magnetic properties using the pseudohalide azide ion and quinolin-8-amine (aqin, C9H8N2) as a chelating ligand, led to the synthesis and structure determination of the title complex, [Fe(N3)2(C9H8N2)2]. The complex shows an octa-hedral geometry, with the FeII atom surrounded by six N atoms; the two N3- anions coordinate in a cis configuration, while the remaining N atoms originate from the two quinolin-8-amine ligands with the quinoline N atoms lying on opposite sides of the Fe atom. The crystal packing is dominated by layers of hydro-philic and aromatic regions parallel to the ac plane, stabilized by a two-dimensional hydrogen-bonded network and π-π stacking.