scholarly journals Cocrystals Based on 4,4’-bipyridine: Influence of Crystal Packing on Melting Point

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 191
Author(s):  
Daniel Ejarque ◽  
Teresa Calvet ◽  
Mercè Font-Bardia ◽  
Josefina Pons
Keyword(s):  
Melting Point ◽  
Carboxylic Acids ◽  
Crystal Packing ◽  
Hirshfeld Surface ◽  
X Ray Diffraction ◽  
Lower Strength ◽  
X Ray ◽  
Molar Ratios ◽  
Acid Acid ◽  
The Difference

The reactions of piperonylic acid (HPip) and cinnamic acid (HCinn) with 4,4’-bipyridine (4,4’-bipy) have been assayed using the same synthetic methodology, yielding two binary cocrystals with different acid:4,4’-bipy molar ratios, (HPip)(4,4’-bipy) (1) and (HCinn)2(4,4’-bipy) (2). The melting point (m.p.) of these cocrystals have been measured and a remarkable difference (ΔT ≈ 78 °C) between them was observed. Moreover, the two cocrystals have been characterized by powder X-ray diffraction (PXRD), elemental analysis (EA), FTIR-ATR, 1H NMR spectroscopies, and single-crystal X-ray diffraction. The study of their structural packings via Hirshfeld surface analysis and energy frameworks revealed the important contribution of the π···π and C-H···π interactions to the formation of different structural packing motifs, this being the main reason for the difference of m.p. between them. Moreover, it has been observed that 1 and 2 presented the same packing motifs as the crystal structure of their corresponding carboxylic acids, but 1 and 2 showed lower m.p. than those of the carboxylic acids, which could be related to the lower strength of the acid-pyridine heterosynthons respect to the acid-acid homosynthons in the crystal structures.

scholarly journals Pressure-induced polymorphism in cyclopropylamine

2005 ◽  
Vol 61 (6) ◽  
pp. 717-723 ◽  
Author(s):  
Patricia Lozano-Casal ◽  
David R. Allan ◽  
Simon Parsons
Keyword(s):  
Crystal Structure ◽  
Crystal Packing ◽  
Hirshfeld Surface ◽  
Amino Group ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
X Ray ◽  
Cell Dimensions ◽  
Graph Set ◽  
Unit Cell Dimensions

The crystal structure of cyclopropylamine at 1.2 GPa has been determined by X-ray diffraction methods. The structure of this phase is orthorhombic, space group Pbca and the unit-cell dimensions are a =  5.0741 (10), b  =  9.7594 (10) and c  =  13.305 (2) Å. Only one of the two H atoms of the amino group actively participates in the formation of the hydrogen-bonded chains, C(2) in graph-set notation, which lie parallel to the crystallographic a axis. Additionally, the topology of the crystal packing is studied using both Voronoi–Dirichlet polyhedra and Hirshfeld surface analyses for the low-temperature and the high-pressure structures of cyclopropylamine and the results are compared.

Three new amidophosphoric acid esters with a P(O)[OCH2C(CH3)2CH2O] segment: X-ray diffraction, DFT, AIM and Hirshfeld surface investigations of bi- and tri-furcated (three and four-center) hydrogen bond interactions

2020 ◽  
Vol 235 (3) ◽  
pp. 69-84 ◽  
Author(s):  
Marjan Sadat Bozorgvar ◽  
Atekeh Tarahhomi ◽  
Arie van der Lee
Keyword(s):  
Hydrogen Bond ◽  
Crystal Packing ◽  
Closed Shell ◽  
Hirshfeld Surface ◽  
Asymmetric Unit ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hydrogen Bond Interactions ◽  
Amidophosphoric Acid ◽  
Acid Esters

AbstractStructural and packing features of three new amidophosphoric acid esters having a common part XP(O)[OCH2C(CH3)2CH2O], with X = [(CH3)3CNH] (1), [(CH3)2HCNH] (2) and [C6H11(CH3)N] (3), are investigated by single crystal X-ray diffraction. The results illustrate that the compounds 1 and 3 crystallize with one independent molecule in the asymmetric unit; whereas, for 2, the compound crystallizes with three independent molecules in the asymmetric unit. The crystal structures are mostly stabilized via tri-furcated hydrogen bond interactions (C–H · · ·)2(N–H · · ·)O=P in 1 and (C–H · · ·)3O=P in 3, while the stability is given by bi-furcated hydrogen bond interactions (C–H · · ·)(N–H · · ·)O=P in 2. For a better understanding of the nature, strength and energetics associated with the formation of the quoted multi-center hydrogen bond interactions, the Natural Bond Order (NBO) method from Density Functional Theory (DFT) and a topological analysis by means of Atoms In Molecules (AIM) and Hirshfeld surface procedures were performed. These studies reveal that the studied multi-center hydrogen bond interactions of the type O · · · H are favoured in the crystal packing displaying enrichment ratios larger than unity. The detailed nature of the different interactions in these multi-center interactions is studied for the first time in such compounds. It is shown that the N–H · · · O interaction is rather non-covalent closed-shell whereas the C–H · · · O interaction is more van der Waals closed-shell. Stronger hydrogen bond interactions are observed for a lower multiple H-atom acceptor oxygen in three-center hydrogen bond interactions (C–H · · ·)(N–H · · ·)O=P of 2 than for four-center interactions in 1 [i.e. (C–H · · ·)2(N–H · · ·)O=P] and 3 [i.e. (C–H · · ·)3O=P]. The better H-atom acceptability of the O atom of P=O compared with the esteric O atom is explained by the richer s-character of the hybrid orbital of the O atom acceptor of P=O coupled with enhance of the polarization and charge. The obtained results are also confirmed by Molecular Electrostatic Potential (MEP).

scholarly journals Crystal structure, optical property and Hirshfeld surface analysis of bis[1-(prop-2-en-1-yl)-1H-imidazol-3-ium] hexachloridostannate(IV)

2020 ◽  
Vol 76 (10) ◽  
pp. 1624-1628
Author(s):  
Hela Ferjani
Keyword(s):  
Surface Analysis ◽  
Crystal Packing ◽  
Three Dimensional ◽  
Hirshfeld Surface ◽  
Molecular Surface ◽  
Hirshfeld Surface Analysis ◽  
X Ray Diffraction ◽  
Visible Absorption ◽  
X Ray ◽  
Uv Visible

A new 0D organic–inorganic hybrid material bis[1-(prop-2-en-1-yl)-1H-imidazol-3-ium] hexachloridostannate(IV), (C6H9N2)2[SnCl6], has been prepared and characterized by single-crystal X-ray diffraction, Hirshfeld surface analysis and UV–visible spectroscopy. The structure consists of isolated [SnCl6]2− octahedral anions separated by layers of organic 1-(prop-2-en-1-yl)-1H-imidazol-3-ium cations. The 1-(prop-2-en-1-yl) fragment in the organic cation exhibits disorder over two sets of atomic sites having occupancies of 0.512 (9) and 0.488 (9). The crystal packing of the title compound is established by intermolecular N/C–H...Cl hydrogen bond and π– π stacking interactions. Hirshfeld surface analysis employing three-dimensional molecular surface contours and two-dimensional fingerprint plots has been used to analyse the intermolecular interactions present in the structure. The optical properties of the crystal were studied using UV–visible absorption spectroscopy, showing one intense band at 208 nm, which is attributed to π–π* transitions in the cations.

scholarly journals Structure cristalline et analyses thermique et de surface Hirshfeld du diperchlorate de 4-azaniumyl-2,2,6,6-tétraméthylpipéridin-1-ium

2017 ◽  
Vol 73 (10) ◽  
pp. 1453-1457 ◽  
Author(s):  
Hammouda Chebbi ◽  
Abdessalem Boumakhla ◽  
Mohamed Faouzi Zid ◽  
Abderrahmen Guesmi
Keyword(s):  
Crystal Packing ◽  
Chair Conformation ◽  
Hirshfeld Surface ◽  
Piperidine Ring ◽  
Dsc Analysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dimensional Network ◽  
Graph Set ◽  
Mixed Layers

The synthesis of 4-azaniumyl-2,2,6,6-tetramethylpiperidin-1-ium diperchlorate, C9H22N22+·2ClO4−, was carried out from an aqueous reaction of perchloric acid with 4-amino-2,2,6,6-tetramethylpiperidine. This compound was characterized by TGA–DSC analysis and single-crystal X-ray diffraction. The piperidine ring of the dication adopts a chair conformation and the orientation of the C—NH3bond is equatorial. One of the two crystallographically independent perchlorate anions exhibits disorder [occupancies 0.625 (7) and 0.375 (7)]. The crystal packing is constituted by a succession of mixed layers parallel to the (-102) plane, made up of C9H22N22+dications and ClO4−anions. These ions are linked by normal and bifurcated N—H...O hydrogen bonds withR44(12) graph-set motifs, generating a two-dimensional network. The intermolecular interactions in the crystal structure were quantified and analysed using Hirshfeld surface analysis.

Supramolecular synthesis based on piperidone derivatives and pharmaceutically acceptable co-formers

2013 ◽  
Vol 69 (4) ◽  
pp. 421-427 ◽  
Author(s):  
Bhupinder Sandhu ◽  
Sergiu Draguta ◽  
Tiffany L. Kinnibrugh ◽  
Victor N. Khrustalev ◽  
Tatiana V. Timofeeva
Keyword(s):  
Crystal Structure ◽  
Melting Point ◽  
Ir Spectroscopy ◽  
Hydrogen Bonds ◽  
Crystal Packing ◽  
Aqueous Solubility ◽  
Active Pharmaceutical Ingredient ◽  
Ethanol Solution ◽  
X Ray Diffraction ◽  
X Ray

The target complexes, bis{(E,E)-3,5-bis[4-(diethylamino)benzylidene]-4-oxopiperidinium} butanedioate, 2C27H36N3O+·C4H4O42−, (II), and bis{(E,E)-3,5-bis[4-(diethylamino)benzylidene]-4-oxopiperidinium} decanedioate, 2C27H36N3O+·C10H16O42−, (III), were obtained by solvent-mediated crystallization of the active pharmaceutical ingredient (API) (E,E)-3,5-bis[4-(diethylamino)benzylidene]-4-piperidone and pharmaceutically acceptable dicarboxylic (succinic and sebacic) acids from ethanol solution. They have been characterized by melting point, IR spectroscopy and single-crystal X-ray diffraction. For the sake of comparison, the structure of the starting API, (E,E)-3,5-bis[4-(diethylamino)benzylidene]-4-piperidone methanol monosolvate, C27H35N3O·CH4O, (I), has also been studied. Compounds (II) and (III) represent salts containing H-shaped centrosymmetric hydrogen-bonded synthons, which are built from two parallel piperidinium cations and a bridging dicarboxylate dianion. In both (II) and (III), the dicarboxylate dianion resides on an inversion centre. The two cations and dianion within the H-shaped synthon are linked by two strong intermolecular N+—H...−OOC hydrogen bonds. The crystal structure of (II) includes two crystallographically independent formula units,AandB. The cation geometries of unitsAandBare different. The main N—C6H4—C=C—C(=O)—C=C—C6H4—N backbone of cationAhas a C-shaped conformation, while that of cationBadopts an S-shaped conformation. The same main backbone of the cation in (III) is practically planar. In the crystal structures of both (II) and (III), intermolecular N+—H...O=C hydrogen bonds between different H-shaped synthons further consolidate the crystal packing, forming columns in the [100] and [10\overline 1] directions, respectively. Salts (II) and (III) possess increased aqueous solubility compared with the original API and thus enhance the bioavailability of the API.

Antiphase Boundaries in Ordered Ni3FE Crystals

1969 ◽  
Vol 27 ◽  
pp. 62-63
Author(s):  
Y. H. Liu
Keyword(s):  
Domain Size ◽  
Antiphase Domain ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hardening Mechanism ◽  
Superlattice Structure ◽  
Disordered Phase ◽  
Domain Boundaries ◽  
Atomic Scattering ◽  
The Difference

Ordered Ni3Fe crystals possess a LI2 type superlattice similar to the Cu3Au structure. The difference in slip behavior of the superlattice as compared with that of a disordered phase has been well established. Cottrell first postulated that the increase in resistance for slip in the superlattice structure is attributed to the presence of antiphase domain boundaries. Following Cottrell's domain hardening mechanism, numerous workers have proposed other refined models also involving the presence of domain boundaries. Using the anomalous X-ray diffraction technique, Davies and Stoloff have shown that the hardness of the Ni3Fe superlattice varies with the domain size. So far, no direct observation of antiphase domain boundaries in Ni3Fe has been reported. Because the atomic scattering factors of the elements in NijFe are so close, the superlattice reflections are not easily detected. Furthermore, the domain configurations in NioFe are thought to be independent of the crystallographic orientations.

scholarly journals Photocatalytic Reduction of CO2 to Methanol Using a Copper-Zirconia Imidazolate Framework

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 346
Author(s):  
Sonam Goyal ◽  
Maizatul Shima Shaharun ◽  
Ganaga Suriya Jayabal ◽  
Chong Fai Kait ◽  
Bawadi Abdullah ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Catalyst Support ◽  
Oxidation Potential ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
X Ray ◽  
Molar Ratios ◽  
Optimum Parameters ◽  
Reduction Of Co2 ◽  
Enhanced Yield

A set of novel photocatalysts, i.e., copper-zirconia imidazolate (CuZrIm) frameworks, were synthesized using different zirconia molar ratios (i.e., 0.5, 1, and 1.5 mmol). The photoreduction process of CO2 to methanol in a continuous-flow stirred photoreactor at pressure and temperature of 1 atm and 25 °C, respectively, was studied. The physicochemical properties of the synthesized catalysts were studied using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectroscopy. The highest methanol activity of 818.59 µmol/L.g was recorded when the CuZrIm1 catalyst with Cu/Zr/Im/NH4OH molar ratio of 2:1:4:2 (mmol/mmol/mmol/M) was employed. The enhanced yield is attributed to the presence of Cu2+ oxidation state and the uniformly dispersed active metals. The response surface methodology (RSM) was used to optimize the reaction parameters. The predicted results agreed well with the experimental ones with the correlation coefficient (R2) of 0.99. The optimization results showed that the highest methanol activity of 1054 µmol/L.g was recorded when the optimum parameters were employed, i.e., stirring rate (540 rpm), intensity of light (275 W/m2) and photocatalyst loading (1.3 g/L). The redox potential value for the CuZrIm1 shows that the reduction potential is −1.70 V and the oxidation potential is +1.28 V for the photoreduction of CO2 to methanol. The current work has established the potential utilization of the imidazolate framework as catalyst support for the photoreduction of CO2 to methanol.

Local atomic structure in tetragonal pure ZrO2nanopowders

2010 ◽  
Vol 43 (2) ◽  
pp. 227-236 ◽  
Author(s):  
Leandro M. Acuña ◽  
Diego G. Lamas ◽  
Rodolfo O. Fuentes ◽  
Ismael O. Fábregas ◽  
Márcia C. A. Fantini ◽  
...  
Keyword(s):  
Tetragonal Phase ◽  
Local Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Atomic Structures ◽  
Crystallite Sizes ◽  
Exafs Study ◽  
The Difference ◽  
X Ray Absorption ◽  
Good Agreement

The local atomic structures around the Zr atom of pure (undoped) ZrO2nanopowders with different average crystallite sizes, ranging from 7 to 40 nm, have been investigated. The nanopowders were synthesized by different wet-chemical routes, but all exhibit the high-temperature tetragonal phase stabilized at room temperature, as established by synchrotron radiation X-ray diffraction. The extended X-ray absorption fine structure (EXAFS) technique was applied to analyze the local structure around the Zr atoms. Several authors have studied this system using the EXAFS technique without obtaining a good agreement between crystallographic and EXAFS data. In this work, it is shown that the local structure of ZrO2nanopowders can be described by a model consisting of two oxygen subshells (4 + 4 atoms) with different Zr—O distances, in agreement with those independently determined by X-ray diffraction. However, the EXAFS study shows that the second oxygen subshell exhibits a Debye–Waller (DW) parameter much higher than that of the first oxygen subshell, a result that cannot be explained by the crystallographic model accepted for the tetragonal phase of zirconia-based materials. However, as proposed by other authors, the difference in the DW parameters between the two oxygen subshells around the Zr atoms can be explained by the existence of oxygen displacements perpendicular to thezdirection; these mainly affect the second oxygen subshell because of the directional character of the EXAFS DW parameter, in contradiction to the crystallographic value. It is also established that this model is similar to another model having three oxygen subshells, with a 4 + 2 + 2 distribution of atoms, with only one DW parameter for all oxygen subshells. Both models are in good agreement with the crystal structure determined by X-ray diffraction experiments.

Problems Associated with Kα Doublet in Residual Stress Measurements

1979 ◽  
Vol 23 ◽  
pp. 333-339
Author(s):  
S. K. Gupta ◽  
B. D. Cullity
Keyword(s):  
Residual Stress ◽  
Silicon Powder ◽  
Lattice Parameter ◽  
Diffraction Peak ◽  
Parameter Determination ◽  
X Ray Diffraction ◽  
X Ray ◽  
Analysis Techniques ◽  
The Difference ◽  
Similar Accuracy

Since the measurement of residual stress by X-ray diffraction techniques is dependent on the difference in angle of a diffraction peak maximum when the sample is examined consecutively with its surface at two different angles to the diffracting planes, it is important that these diffraction angles be obtained precisely, preferably with an accuracy of ± 0.01 deg. 2θ. Similar accuracy is desired in precise lattice parameter determination. In such measurements, it is imperative that the diffractometer be well-aligned. It is in the context of diffractometer alignment with the aid of a silicon powder standard free of residual stress that the diffraction peak analysis techniques described here have been developed, preparatory to residual stress determinations.

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