scholarly journals Engineering short, strong hydrogen bonds in urea di-carboxylic acid complexes

CrystEngComm ◽  
2014 ◽  
Vol 16 (35) ◽  
pp. 8177-8184 ◽  
Author(s):  
Andrew O. F. Jones ◽  
Charlotte K. Leech ◽  
Garry J. McIntyre ◽  
Chick C. Wilson ◽  
Lynne H. Thomas
Keyword(s):  
Hydrogen Bond ◽  
Carboxylic Acid ◽  
Hydrogen Bonds ◽  
Neutron Diffraction ◽  
Structural Changes ◽  
Acid Amide ◽  
Molecular Complexes ◽  
Temperature Dependent ◽  
X Ray ◽  
Methyl Substitution

The persistence of the acid⋯amide heterodimer and the effect of methyl substitution on the short strong O–H⋯O hydrogen bond is investigated in urea and methylurea di-carboxylic acid molecular complexes. Temperature dependent structural changes are also reported utilising X-ray and neutron diffraction in tandem.

scholarly journals Variable-temperature neutron diffraction studies of the short, strong hydrogen bonds in the crystal structure of pyridine-3,5-dicarboxylic acid

2005 ◽  
Vol 61 (6) ◽  
pp. 724-730 ◽  
Author(s):  
John. A. Cowan ◽  
Judith A. K. Howard ◽  
Garry, J. McIntyre ◽  
Samuel M.-F Lo ◽  
Ian D. Williams
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Carboxylic Acid ◽  
Hydrogen Bonds ◽  
Neutron Diffraction ◽  
Dicarboxylic Acid ◽  
Bond Length ◽  
Variable Temperature ◽  
Temperature Dependent ◽  
Proton Migration

Pyridine-3,5-dicarboxylic acid has been studied by single-crystal neutron diffraction at 15 and 296 K. Pyridine-3,5-dicarboxylic acid, in which the carboxylic acid protons have been replaced by deuterons, has also been studied at 15, 150 and 296 K. The protonated structure contains a short N...H...O hydrogen bond [N...O 2.523 (2) Å at 15 K]. Temperature-dependent proton migration occurs where the N—H distance in the hydrogen bond changes from 1.213 (4) Å at 15 K to 1.308 (6) Å at 300 K. In the deuterated structure the overall hydrogen-bond length increased [N...O 2.538 (3) Å at 15 K] and the magnitude of the migration increased so that the N—D distance changes from 1.151 (3) Å at 15 K to 1.457 (4) Å at 300 K.

The whole range of hydrogen bonds in one crystal structure: neutron diffraction and charge-density studies of N,N-dimethylbiguanidinium bis(hydrogensquarate)

2011 ◽  
Vol 67 (6) ◽  
pp. 552-559 ◽  
Author(s):  
Mihaela-Diana Şerb ◽  
Ruimin Wang ◽  
Martin Meven ◽  
Ulli Englert
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
High Resolution ◽  
Hydrogen Bonds ◽  
Neutron Diffraction ◽  
Electron Density ◽  
Organic Salt ◽  
X Ray Diffraction ◽  
Covalent Character ◽  
X Ray

N,N-Dimethylbiguanidinium bis(hydrogensquarate) features an impressive range of hydrogen bonds within the same crystal structure: neighbouring anions aggregate to a dianionic pair through two strong O—H...O interactions; one of these can be classified among the shortest hydrogen bonds ever studied. Cations and anions in this organic salt further interact via conventional N—H...O and nonclassical C—H...O contacts to an extended structure. As all these interactions occur in the same sample, the title compound is particularly suitable to monitor even subtle trends in hydrogen bonds. Neutron and high-resolution X-ray diffraction experiments have enabled us to determine the electron density precisely and to address its properties with an emphasis on the nature of the X—H...O interactions. Sensitive criteria such as the Laplacian of the electron density and energy densities in the bond-critical points reveal the incipient covalent character of the shortest O—H...O bond. These findings are in agreement with the precise geometry from neutron diffraction: the shortest hydrogen bond is also significantly more symmetric than the longer interactions.

scholarly journals On hydrogen bonding in 1,6-anhydro-β-D-glucopyranose (levoglucosan): X-ray and neutron diffraction and DFT study

2006 ◽  
Vol 62 (5) ◽  
pp. 912-918 ◽  
Author(s):  
Ľubomír Smrčok ◽  
Mariana Sládkovičová ◽  
Vratislav Langer ◽  
Chick C. Wilson ◽  
Miroslav Koóš
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Solid State ◽  
Hydrogen Bonds ◽  
Neutron Diffraction ◽  
Dft Calculations ◽  
Diffraction Data ◽  
Neutron Diffraction Study ◽  
Single Crystal Diffraction ◽  
X Ray

The geometry of hydrogen bonds in 1,6-anhydro-β-D-glucopyranose (levoglucosan) is accurately determined by refinement of time-of-flight neutron single-crystal diffraction data. Molecules of levoglucosan are held together by a hydrogen-bond array formed by a combination of strong O—H...O and supporting weaker C—H...O bonds. These are fully and accurately detailed by the neutron diffraction study. The strong hydrogen bonds link molecules in finite chains, with hydroxyl O atoms acting as both donors and acceptors of hydroxyl H atoms. A comparison of molecular and solid-state DFT calculations predicts red shifts of O—H and associated blue shifts of C—H stretching frequencies due to the formation of hydrogen bonds in this system.

Neutron diffraction of a complex of 1,8-bis(dimethylamino)naphthalene with 1,2-dichloromaleic acid

1996 ◽  
Vol 52 (4) ◽  
pp. 691-696 ◽  
Author(s):  
K. Wozniak ◽  
C. C. Wilson ◽  
K. S. Knight ◽  
W. Jones ◽  
E. Grech
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Neutron Diffraction ◽  
Strong Correlation ◽  
Equivalent Temperature ◽  
Neutron Data ◽  
Crystalline Complex ◽  
X Ray ◽  
Temperature Factors ◽  
Atom Temperature

A neutron study of the crystalline complex of 1,8-bis(dimethylamino)naphthalene (DMAN) with 1,2-dichloromaleic acid (ClMH2) has been carried out at 100 K using the Laue time-of-flight technique. The moieties are planar. The neutron data indicate that both [N—H...N]+ and [O—H...O]− hydrogen bonds in the complex are asymmetric. There are significant differences between the neutron and X-ray temperature factors, C—H, N—H and O—H bond lengths. There is a strong correlation between the neutron and X-ray temperature factors for non-H atoms and no correlation for H-atom temperature factors. According to the neutron data the involvement of a given H atom in a weak C—H...O hydrogen bond can be correlated with the ratio of equivalent temperature factors of the H and non-H atoms to which they are attached.

Hirshfeld atom refinement for modelling strong hydrogen bonds

2014 ◽  
Vol 70 (5) ◽  
pp. 483-498 ◽  
Author(s):  
Magdalena Woińska ◽  
Dylan Jayatilaka ◽  
Mark A. Spackman ◽  
Alison J. Edwards ◽  
Paulina M. Dominiak ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Atom ◽  
Low Temperature ◽  
Hydrogen Bonds ◽  
Neutron Diffraction ◽  
Electron Density ◽  
Diffraction Experiment ◽  
Neutron Diffraction Experiment ◽  
X Ray ◽  
Atom Model

High-resolution low-temperature synchrotron X-ray diffraction data of the salt L-phenylalaninium hydrogen maleate are used to test the new automated iterative Hirshfeld atom refinement (HAR) procedure for the modelling of strong hydrogen bonds. The HAR models used present the first examples ofZ′ > 1 treatments in the framework of wavefunction-based refinement methods. L-Phenylalaninium hydrogen maleate exhibits several hydrogen bonds in its crystal structure, of which the shortest and the most challenging to model is the O—H...O intramolecular hydrogen bond present in the hydrogen maleate anion (O...O distance is about 2.41 Å). In particular, the reconstruction of the electron density in the hydrogen maleate moiety and the determination of hydrogen-atom properties [positions, bond distances and anisotropic displacement parameters (ADPs)] are the focus of the study. For comparison to the HAR results, different spherical (independent atom model, IAM) and aspherical (free multipole model, MM; transferable aspherical atom model, TAAM) X-ray refinement techniques as well as results from a low-temperature neutron-diffraction experiment are employed. Hydrogen-atom ADPs are furthermore compared to those derived from a TLS/rigid-body (SHADE) treatment of the X-ray structures. The reference neutron-diffraction experiment reveals a truly symmetric hydrogen bond in the hydrogen maleate anion. Only with HAR is it possible to freely refine hydrogen-atom positions and ADPs from the X-ray data, which leads to the best electron-density model and the closest agreement with the structural parameters derived from the neutron-diffraction experiment,e.g.the symmetric hydrogen position can be reproduced. The multipole-based refinement techniques (MM and TAAM) yield slightly asymmetric positions, whereas the IAM yields a significantly asymmetric position.

The crystal structure of deuterated trans-Tetraamminedinitronickel(II) at 4.2 K by neutron diffraction

1981 ◽  
Vol 34 (5) ◽  
pp. 993 ◽  
Author(s):  
BN Figgis ◽  
PA Reynolds ◽  
GA Williams ◽  
N Lehner
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Neutron Diffraction ◽  
Rigid Body ◽  
Large Amplitude ◽  
Translational Motion ◽  
Axial Direction ◽  
Full Matrix ◽  
X Ray

The crystal structure of deuterated trans-tetraamminedinitronickel(II), Ni(ND3)4(NO2)2, has been determined by single-crystal neutron diffraction methods at 4·2 K. Crystals are monoclinic, C2/m, a 1058(l), b 672(1), c 586.3(3) pm, β 114.82(5)�, Z = 2. Diffractometry has provided Bragg intensities for 219 independent reflections; and the structure has been refined by full-matrix least-squares methods to R(F2) 0·070 and χ2 3·8. There are slight differences in the molecular geometries determined by neutron diffraction and earlier X-ray determinations of Ni(NH3)4(NO2)2 at 295 and 130 K. Small, but significant, decreases are evident in all non-hydrogen bond lengths on decrease in temperature from 295 to 4·2 K, up to a maximum of 2·0(4) pm for the Ni-NH3/ND3 bond. The magnitudes of these decreases are correlated with the force constants of the bonds. The intermolecular geometry and thermal parameters show that in the ab plane there is a network of relatively strong, linear N-D···O hydrogen bonds. In the c* direction there is a slightly bent, longer, N-D(1)···O bond which is weaker. This causes a large amplitude of rigid-body translational motion in the c* direction, together with high thermal motion of D(1) in the b axial direction.

The Effect of Different Hydrogen Bonding Schemes on Melting Points of Two Isomeric 2-Hydroxy-bornane-3-carboxylic Acids

2000 ◽  
Vol 55 (8) ◽  
pp. 671-676 ◽  
Author(s):  
Maciej Kubicki ◽  
Teresa Borowiak ◽  
Wiesław Z. Antkowiak
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Melting Point ◽  
Carboxylic Acid ◽  
Hydrogen Bonds ◽  
Intermolecular Hydrogen Bond ◽  
Melting Points ◽  
Intermolecular Hydrogen Bonds ◽  
X Ray ◽  
Single Crystal Analysis

Abstract The crystal structures of two isomeric compounds, 2-endo-hydroxybornane-3-endo-carboxylic acid and 2 -exo -hydroxybomane-3 -endo-carboxylic acid, have been determined by X-ray single crystal analysis. The only difference between these two compounds is the disposition of the 2-hydroxy group with respect to the bomane skeleton. Both compounds show quite different hydrogen bonding schemes. In the endo-hydroxy-endo-carboxy isomer there is one intramolecular and one intermolecular hydrogen bond, which connects molecules into infinite chains, while in the exo-hydroxy-endo-carboxy isomer there are two intermolecular hydrogen bonds that form a more stable architecture of two kinds of chains which interconnect to close rings comprising four molecules. Due to these differences the melting point of 2 is ca. 30° higher than for 1 .

Crystal structure of tofacitinib dihydrogen citrate (Xeljanz®), (C16H21N6O)(H2C6H5O7)

2021 ◽  
pp. 1-8
Author(s):  
James A. Kaduk ◽  
Amy M. Gindhart ◽  
Thomas N. Blanton
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Carboxylic Acid ◽  
Hydrogen Bonds ◽  
Powder Diffraction ◽  
Density Functional ◽  
Acid Group ◽  
Dimensional Network ◽  
Van Der Waals Contacts ◽  
Citrate Anion

The crystal structure of tofacitinib dihydrogen citrate (tofacitinib citrate) has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional techniques. Tofacitinib dihydrogen citrate crystallizes in space group P212121 (#19) with a = 5.91113(1), b = 12.93131(3), c = 30.43499(7) Å, V = 2326.411(6) Å3, and Z = 4. The crystal structure consists of corrugated layers perpendicular to the c-axis. Within the layers, cation⋯anion and anion⋯anion hydrogen bonds link the fragments into a two-dimensional network parallel to the ab-plane. Between the layers, there are only van der Waals contacts. A terminal carboxylic acid group in the citrate anion forms a strong charge-assisted hydrogen bond to the ionized central carboxylate group. The other carboxylic acid acts as a donor to the carbonyl group of the cation. The citrate hydroxy group forms an intramolecular charge-assisted hydrogen bond to the ionized central carboxylate. Two protonated nitrogen atoms in the cation act as donors to the ionized central carboxylate of the anion. These hydrogen bonds form a ring with the graph set symbol R2,2(8). The powder pattern has been submitted to ICDD® for inclusion in the Powder Diffraction File™ (PDF®).

scholarly journals Acemetacin cocrystals and salts: structure solution from powder X-ray data and form selection of the piperazine salt

IUCrJ ◽  
2014 ◽  
Vol 1 (2) ◽  
pp. 136-150 ◽  
Author(s):  
Palash Sanphui ◽  
Geetha Bolla ◽  
Ashwini Nangia ◽  
Vladimir Chernyshev
Keyword(s):  
Hydrogen Bonds ◽  
Dissolution Rate ◽  
Aqueous Medium ◽  
Acid Amide ◽  
Three Dimensional ◽  
X Ray Diffraction ◽  
Reference Drug ◽  
X Ray ◽  
Time Period ◽  
Solid Form

Acemetacin (ACM) is a non-steroidal anti-inflammatory drug (NSAID), which causes reduced gastric damage compared with indomethacin. However, acemetacin has a tendency to form a less soluble hydrate in the aqueous medium. We noted difficulties in the preparation of cocrystals and salts of acemetacin by mechanochemical methods, because this drug tends to form a hydrate during any kind of solution-based processing. With the objective to discover a solid form of acemetacin that is stable in the aqueous medium, binary adducts were prepared by the melt method to avoid hydration. The coformers/salt formers reported are pyridine carboxamides [nicotinamide (NAM), isonicotinamide (INA), and picolinamide (PAM)], caprolactam (CPR),p-aminobenzoic acid (PABA), and piperazine (PPZ). The structures of an ACM–INA cocrystal and a binary adduct ACM–PABA were solved using single-crystal X-ray diffraction. Other ACM cocrystals, ACM–PAM and ACM–CPR, and the piperazine salt ACM–PPZ were solved from high-resolution powder X-ray diffraction data. The ACM–INA cocrystal is sustained by the acid...pyridine heterosynthon and N—H...O catemer hydrogen bonds involving the amide group. The acid...amide heterosynthon is present in the ACM–PAM cocrystal, while ACM–CPR contains carboxamide dimers of caprolactam along with acid–carbonyl (ACM) hydrogen bonds. The cocrystals ACM–INA, ACM–PAM and ACM–CPR are three-dimensional isostructural. The carboxyl...carboxyl synthon in ACM–PABA posed difficulty in assigning the position of the H atom, which may indicate proton disorder. In terms of stability, the salts were found to be relatively stable in pH 7 buffer medium over 24 h, but the cocrystals dissociated to give ACM hydrate during the same time period. The ACM–PPZ salt and ACM–nicotinamide cocrystal dissolve five times faster than the stable hydrate form, whereas the ACM–PABA adduct has 2.5 times faster dissolution rate. The pharmaceutically acceptable piperazine salt of acemetacin exhibits superior stability, faster dissolution rate and is able to overcome the hydration tendency of the reference drug.

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