scholarly journals Synthesis and structure of tricarbonyl(η6-arene)chromium complexes of phenyl and benzyl D-glycopyranosides

2012 ◽  
Vol 8 ◽  
pp. 1059-1070 ◽  
Author(s):  
Thomas Ziegler ◽  
Ulrich Heber
Keyword(s):  
Hydrogen Bonds ◽  
X Ray Diffraction ◽  
Chromium Complexes ◽  
X Ray ◽  
Tricarbonylchromium Complexes

A series of 15 glycoside-derived tricarbonyl(η6-arene)chromium complexes were prepared in 19–87% yield by heating fully acetylated or methylated aryl O-, S-, N- and C-glycosides of D-glucopyranose and D-mannopyranose with hexacarbonylchromium. All tricarbonylchromium complexes were fully characterized. The structures of nine crystalline complexes were determined by X-ray diffraction, revealing unusual intra- and intermolecular nonclassical hydrogen bonds.

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.

scholarly journals Crystal structure of 3-benzyl-2-[(E)-2-(furan-2-yl)ethenyl]-2,3-dihydroquinazolin-4(1H)-one and 3-benzyl-2-[(E)-2-(thiophen-2-yl)ethenyl]-2,3-dihydroquinazolin-4(1H)-one from synchrotron X-ray diffraction

2018 ◽  
Vol 74 (1) ◽  
pp. 10-14
Author(s):  
Flavien A. A. Toze ◽  
Vladimir P. Zaytsev ◽  
Lala V. Chervyakova ◽  
Elisaveta A. Kvyatkovskaya ◽  
Pavel V. Dorovatovskii ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Axial Position ◽  
Isatoic Anhydride ◽  
X Ray Diffraction ◽  
X Ray ◽  
Bond Angles ◽  
Pyramidal Geometry ◽  
Three Component Reaction ◽  
Racemic Crystals

The chiral title compounds, C21H18N2O2, (I), and C21H18N2OS, (II) – products of the three-component reaction between benzylamine, isatoic anhydride and furyl- or thienyl-acrolein – are isostructural and form isomorphous racemic crystals. The tetrahydropyrimidine ring in (I) and (II) adopts a sofa conformation. The amino N atom has a trigonal–pyramidal geometry [sum of the bond angles is 347.0° for both (I) and (II)], whereas the amido N atom is flat [sum of the bond angles is 359.3° for both (I) and (II)]. The furyl- and thienylethenyl substituents in (I) and (II) are planar and the conformation about the bridging C=C bond isE. These bulky fragments occupy the axial position at the quaternary C atom of the tetrahydropyrimidine ring, apparently, due to steric reasons. In the crystals, molecules of (I) and (II) form hydrogen-bonded helicoidal chains propagating along [010] by strong intermolecular N—H...O hydrogen bonds.

Crystal and molecular structure of diorganoammonium oxalatotrimethylstannate, [R2NH2][Me3Sn(C2O4)] (R=i-Bu, cyclohexyl)

2011 ◽  
Vol 34 (5-6) ◽  
pp. 127-130 ◽  
Author(s):  
Yaya Sow ◽  
Libasse Diop ◽  
Kieran C. Molloy ◽  
Gabrielle Kociok-Köhn
Keyword(s):  
Molecular Structure ◽  
Hydrogen Bonds ◽  
Diffraction Study ◽  
Crystal And Molecular Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Trigonal Bipyramidal ◽  
Trans Complex ◽  
A Chain ◽  
Distorted Trigonal Bipyramidal

Abstract The title compounds [R2NH2][C2O4SnMe3](R=i-Bu, Cy), in which tin atoms adopt a distorted trigonal bipyramidal configuration, have been prepared and submitted to an X-ray diffraction study. These compounds have been obtained from the reaction of (Cy2NH2)2C2O4·H2O or (i-Bu2NH2)2C2O4 with SnMe3Cl. In both [R2NH2][C2O4SnMe3] compounds, the trans complex has an almost regular trigonal bipyramidal geometry around the tin atom. The SnMe3 residues are connected as a chain with bridging oxalate anions in a trans-SnC3O2 framework, the oxygen atoms being in axial positions. The cations connect linear adjacent chains through NH…O hydrogen bonds giving layered structures.

Salts of purine alkaloids caffeine and theobromine with 2,6-dihydroxybenzoic acid as coformer: structural, theoretical, thermal and spectroscopic studies

2021 ◽  
Vol 77 (11) ◽  
Author(s):  
Mateusz Gołdyn ◽  
Anna Komasa ◽  
Mateusz Pawlaczyk ◽  
Aneta Lewandowska ◽  
Elżbieta Bartoszak-Adamska
Keyword(s):  
Hydrogen Bonds ◽  
Water Solubility ◽  
Theoretical Calculations ◽  
Spectroscopic Studies ◽  
X Ray Diffraction ◽  
Dihydroxybenzoic Acid ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Purine Alkaloids ◽  
Vis Spectroscopy

The study of various forms of pharmaceutical substances with specific physicochemical properties suitable for putting them on the market is one of the elements of research in the pharmaceutical industry. A large proportion of active pharmaceutical ingredients (APIs) occur in the salt form. The use of an acidic coformer with a given structure and a suitable pK a value towards purine alkaloids containing a basic imidazole N atom can lead to salt formation. In this work, 2,6-dihydroxybenzoic acid (26DHBA) was used for cocrystallization of theobromine (TBR) and caffeine (CAF). Two novel salts, namely, theobrominium 2,6-dihydroxybenzoate, C7H9N4O2 +·C7H5O4 − (I), and caffeinium 2,6-dihydroxybenzoate, C8H11N4O2 +·C7H5O4 − (II), were synthesized. Both salts were obtained independently by slow evaporation from solution, by neat grinding and also by microwave-assisted slurry cocrystallization. Powder X-ray diffraction measurements proved the formation of the new substances. Single-crystal X-ray diffraction studies confirmed proton transfer between the given alkaloid and 26DHBA, and the formation of N—H...O hydrogen bonds in both I and II. Unlike the caffeine cations in II, the theobromine cations in I are paired by noncovalent N—H...O=C interactions and a cyclic array is observed. As expected, the two hydroxy groups in the 26DHBA anion in both salts are involved in two intramolecular O—H...O hydrogen bonds. C—H...O and π–π interactions further stabilize the crystal structures of both compounds. Steady-state UV–Vis spectroscopy showed changes in the water solubility of xanthines after ionizable complex formation. The obtained salts I and II were also characterized by theoretical calculations, Fourier-transform IR spectroscopy (FT–IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and elemental analysis.

Thermal-induced transformation of glutamic acid to pyroglutamic acid and self-cocrystallization: a charge–density analysis

2022 ◽  
Vol 78 (2) ◽  
Author(s):  
Sehrish Akram ◽  
Arshad Mehmood ◽  
Sajida Noureen ◽  
Maqsood Ahmed
Keyword(s):  
Hydrogen Bonds ◽  
Glutamic Acid ◽  
Single Crystal ◽  
Diffraction Data ◽  
Density Functional ◽  
Quantitative Estimation ◽  
Topological Analysis ◽  
Pyroglutamic Acid ◽  
X Ray Diffraction ◽  
X Ray

Thermal-induced transformation of glutamic acid to pyroglutamic acid is well known. However, confusion remains over the exact temperature at which this happens. Moreover, no diffraction data are available to support the transition. In this article, we make a systematic investigation involving thermal analysis, hot-stage microscopy and single-crystal X-ray diffraction to study a one-pot thermal transition of glutamic acid to pyroglutamic acid and subsequent self-cocrystallization between the product (hydrated pyroglutamic acid) and the unreacted precursor (glutamic acid). The melt upon cooling gave a robust cocrystal, namely, glutamic acid–pyroglutamic acid–water (1/1/1), C5H7NO3·C5H9NO4·H2O, whose structure has been elucidated from single-crystal X-ray diffraction data collected at room temperature. A three-dimensional network of strong hydrogen bonds has been found. A Hirshfeld surface analysis was carried out to make a quantitative estimation of the intermolecular interactions. In order to gain insight into the strength and stability of the cocrystal, the transferability principle was utilized to make a topological analysis and to study the electron-density-derived properties. The transferred model has been found to be superior to the classical independent atom model (IAM). The experimental results have been compared with results from a multipolar refinement carried out using theoretical structure factors generated from density functional theory (DFT) calculations. Very strong classical hydrogen bonds drive the cocrystallization and lend stability to the resulting cocrystal. Important conclusions have been drawn about this transition.

Silver(I)-Saccharinato Complexes with 2-(Aminomethyl)pyridine and 2-(2-Aminoethyl)pyridine Ligands: [Ag(sac)(ampy)] and [Ag2(sac)2(μ-aepy)2]

2005 ◽  
Vol 60 (9) ◽  
pp. 978-983 ◽  
Author(s):  
Sevim Hamamci ◽  
Veysel T. Yilmaz ◽  
William T. A. Harrison
Keyword(s):  
Thermal Analysis ◽  
Hydrogen Bonds ◽  
Monoclinic Space Group ◽  
Stacking Interactions ◽  
Coordination Geometry ◽  
X Ray Diffraction ◽  
Triclinic Space Group ◽  
Space Group ◽  
X Ray ◽  
Pyridine Ligands

Two new saccharinato-silver(I) (sac) complexes, [Ag(sac)(ampy)] (1), and [Ag2(sac)2(μ-aepy)2] (2), [ampy = 2-(aminomethyl)pyridine, aepy = 2-(2-aminoethyl)pyridine], have been prepared and characterized by elemental analysis, IR spectroscopy, thermal analysis and single crystal X-ray diffraction. Complexes 1 and 2 crystallize in the monoclinic space group P21/c and triclinic space group P1̄, respectively. The silver(I) ions in both complexes 1 and 2 exhibit a distorted T-shaped AgN3 coordination geometry. 1 consists of individual molecules connected into chains by N-H···O hydrogen bonds. There are two crystallographically distinct dimers in the unit cell of 2 and in each dimer, the aepy ligands act as a bridge between two silver(I) centers, resulting in short argentophilic contacts [Ag1···Ag1 = 3.0199(4) Å and Ag2···Ag2 = 2.9894(4) Å ]. Symmetry equivalent dimers of 2 are connected by N-H···O hydrogen bonds into chains, which are further linked by aromatic π(py)···π(py) stacking interactions into sheets.

6π-Tricarbonyl-Komplexe von Pyridin-Derivaten, Synthesen und Reaktionen / 6π-Tricarbonyl-Chromium Complexes of Pyridine Derivatives, Syntheses and Reactions

1984 ◽  
Vol 39 (2) ◽  
pp. 207-212 ◽  
Author(s):  
Karl Dimroth ◽  
Rüdiger Thamm ◽  
Hans Kaletsch
Keyword(s):  
Hydrogen Atom ◽  
Phosphorus Atom ◽  
Nmr Spectra ◽  
Pyridine Derivatives ◽  
Chromium Complexes ◽  
X Ray ◽  
Chromium Hexacarbonyl ◽  
Allyl Rearrangement ◽  
Tricarbonylchromium Complexes ◽  
C Nmr

New 6π-tricarbonylchromiumpyrnftne complexes 5c and 5d could be synthesized from 2,6-di-rbutyl- and 2,4,6-tri-f-butylpyridines (3c and 3d) with chromium hexacarbonyl. They are characterized by their 1H and 13C NMR Spectra and their CO-frequencies which are rather similar to those of 6π-tricarbonylchromium-2,4 ,6-triphenyl [1] or 2,4,6-trw-butyl- [2] λ3-phosphorins. When 5d is reacted with lithiumphenyl, the phenyl residue adds to C-4, giving probably compound 7, which by methanolysis and allyl rearrangement of the hydrogen atom from position 4 to position 2 affords tricarbonylchromium-2,6-di-f-butyl-4-phenyl-1,2-dihydropyridine (8) in 56% yield. The 6π-tricarbonylchromium complexes of 2,4,6-triphenyl- or 2,4,6-tn-t-butyl-λ3-phosphorins react with lithiumorganic compounds by addition only to the phosphorus atom whose reaction with methyliodide lead to tricarbonylchromium-λ5-phosphorin-ylid complexes [2], 5 d is a well crystallized compound, the X-ray analysis of the first 6π-tricarbonylchromium pyridine derivate could be performed [3] and compared with the results of the X-ray analysis of 6π-tricarbonylchromiumx 2,4,6-triphenyl-λ3-phosphorin [4]

Evolution structurale de la nacrite en fonction de la nature des molécules organiques intercalees

2000 ◽  
Vol 33 (6) ◽  
pp. 1351-1359 ◽  
Author(s):  
A. Ben Haj Amara ◽  
H. Ben Rhaiem ◽  
A. Plançon
Keyword(s):  
Ir Spectroscopy ◽  
Hydrogen Bonds ◽  
Dimethyl Sulfoxide ◽  
Organic Molecules ◽  
Interlayer Space ◽  
X Ray Diffraction ◽  
X Ray ◽  
Intercalated Compounds ◽  
Xrd Study ◽  
Intercalation Process

Nacrite has been intercalated with two polar organic molecules: dimethyl sulfoxide (DMSO) andN-methylacetamide (NMA). The homogeneous nacrite complexes have been studied by X-ray diffraction (XRD) and infrared (IR) spectroscopy. The XRD study is based on a comparison between experimental and calculated patterns. The structures of the intercalated compounds have been determined, including the mutual positions of the layers after intercalation and the positions of the intercalated molecules in the interlayer space. It has been shown that the intercalation process causes not only a swelling of the interlayer space but also a shift in the mutual in-plane positions of the layers. This shift depends on the nature of the intercalated molecules and is related to their shape and the hydrogen bonds which are established with the surrounding surfaces. For a given molecule, the intercalation process is the same for the different polytypes of the kaolinite family. These XRD results are consistent with those of IR spectroscopy.

Improved Enzymatic Depolymerization of Chitosan by Ionic Liquid Pretreatment and the Effect of Oligo-Chitosan on Intestinal Flora In Vitro

2011 ◽  
Vol 391-392 ◽  
pp. 1319-1323
Author(s):  
Cui Zheng ◽  
Lin Li ◽  
Hao Pang ◽  
Zhao Mei Wang ◽  
Na Li
Keyword(s):  
Ionic Liquid ◽  
Hydrogen Bonds ◽  
Molecular Hydrogen ◽  
Intestinal Flora ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hydrolysis Of ◽  
Positive Effect ◽  
Enzymatic Depolymerization

It still remains challenging for effective hydrolysis of chitosan into chitosan oligomers. In this work, a pretreatment was conducted on chitosan by an ionic liquid 1-butyl-3-methylimidazolium chloride ([C4mim]Cl), aiming at improving enzymatic depolymerization of chitosan. X-ray diffraction analysis indicated that the inter- and intra-molecular hydrogen bonds within chitosan molecules were broken by [C4mim]Cl and the crystalline was destroyed. The oligo-chitosan hydrolyzed from IL-pretreated chitosan, coded as COS-IL, showed a DP of 3~5, in contrast to DP 5~8 with oligo-chitosan obtained from untreated chitosan(coded as COS-UN). COS-IL was more effective than COS-UN in inhibiting intestinal spoilage bacterials growth and it has positive effect on the growth of intestinal probiotic bacterials.

Synthese und Kristallstrukturen einiger Tetramethylstibonium-Hydrogendicarboxylate / Synthesis and Crystal Structures of Some Tetramethylstibonium Hydrogendicarboxylates

1982 ◽  
Vol 37 (11) ◽  
pp. 1393-1401 ◽  
Author(s):  
Beatrix Milewski-Mahrla ◽  
Hubert Schmidbaur
Keyword(s):  
Hydrogen Bonds ◽  
Crystal Structures ◽  
Spectroscopic Data ◽  
Molar Ratio ◽  
Ionic Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Carboxylate Oxygen ◽  
Donor Acceptor ◽  
New Compounds

Reactions of pentamethylantimony (CH3)5Sb with carboxylic acids in the molar ratio 1:2 afford one equivalent of methane and essentially quantitative yields of crystalline tetramothylstibonium hydrogendicarboxylates. Six new compounds of this series have been synthesized using benzoic, o-phthalic, salicylic, 4-ethoxy-salicylic, oxalic, and malic acid, and characterized by analytical and spectroscopic data. An ionic structure with strong hydrogen bonds in the anionic components is proposed.The crystal structures of the hydrogen-dibenzoato (1), hydrogen-ortho-plithalato (2) and 4-ethoxy-hydrogen-salicylate (3) were determined by single crystal X-ray diffraction. The compounds can be described as having ionic lattices with some donor-acceptor inter­actions between the stibonium centers and the carboxylate oxygen atoms. The anions are characterized by strong hydrogen bonds O...H...O. Thus, the (CH3)4Sb-tetrahedron in 1 is distorted by two benzoate oxygon atoms (at 304(2) and 340(2) pin). The cation in 2 is largely undistorted and the anion has a hydrogenphthalate hydrogen bond of d(O...H...O) = 232 pm. The cation-anion contact in 3 is as short as d(Sb-O) = 289 pm rendering the Sb atom pentacoordinate.

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