Special Issue "Characterisation and Study of Compounds by Single Crystal X-Ray Diffraction"

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Crystal Engineering".

Deadline for manuscript submissions: 1 October 2019.

Special Issue Editor

Guest Editor
Dr. Josefina Perles Website E-Mail
Laboratorio de Difracción de Rayos X de Monocristal, SIdI, Universidad Autónoma de Madrid, 28049 Madrid, Spain
Interests: single crystal X-ray diffraction; structure-properties relationship; supramolecular interactions; topological studies

Special Issue Information

Dear Colleagues,

X-ray diffraction has been widely regarded as the most powerful technique for the structural study of crystalline samples during the last century, as it provides detailed information about the atomic structure of ordered solids regardless of the chemical nature of the sample. Although in the early days it was mostly applied to mineral samples, the crystallisation of natural biological molecules and new synthetic compounds has extended the application of this technique to other disciplines such as chemistry, biology, materials science or pharmacology.

In particular, single crystal X-ray diffraction (SCXRD) has played a crucial role in the interpretation of the physicochemical properties of many substances, determining with high precision the location of the atoms in the crystal as well as the strength of interatomic bonds and supramolecular interactions. Advances in data collection and treatment have overcome many of the initial limitations such as small crystal size, twinning or poor crystallinity of the sample, and today SCXRD is a unique characterisation tool for many scientists.

In this Special Issue, on the topic “Characterisation and Study of Compounds by Single Crystal X-ray Diffraction”, we want to highlight the importance of this technique in scientific research, alone or in combination with other analytical methods. All contributions involving SCXRD are welcome, and especially those studies in which SCXRD has provided key information to solve experimental problems.

Kind regards,

Dr. Josefina Perles
Guest Editor

Manuscript Submission Information

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Keywords

  • crystal structure
  • SCXRD
  • X-ray crystallography
  • structural study

Published Papers (4 papers)

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Research

Open AccessArticle
Site Selectivity of Halogen Oxygen Bonding in 5- and 6-Haloderivatives of Uracil
Crystals 2019, 9(9), 467; https://doi.org/10.3390/cryst9090467 - 06 Sep 2019
Abstract
Seven 5-and 6-halogenated derivatives of uracil or 1-methyluracil (halogen = Cl, Br, I) were studied by single crystal X-ray diffraction. In contrast with pure 5-halouracils, where the presence of N-HO and C-HO hydrogen bonds prevents the formation of other [...] Read more.
Seven 5-and 6-halogenated derivatives of uracil or 1-methyluracil (halogen = Cl, Br, I) were studied by single crystal X-ray diffraction. In contrast with pure 5-halouracils, where the presence of N-HO and C-HO hydrogen bonds prevents the formation of other intermolecular interactions, the general ability of pyrimidine nucleobases to provide electron donating groups to halogen bonding was confirmed in three crystals and cocrystals containing uracil with the halogen atom at the C6 position. In the latter compounds, among the two nucleophilic oxygen atoms in the C=O moiety, only the urea carbonyl oxygen O1 can act as halogen bond acceptor, being not saturated by conventional hydrogen bonds. The halogen bonds in pure 6-halouracils are all rather weak, as supported by Hirshfeld surface analysis. The strongest interaction was found in the structure of 6-iodouracil, which displayed the largest (13%) reduction of the sum of van der Waals (vdW) radii for the contact atoms. Despite this, halogen bonding plays a role in determining the crystal packing of 6-halouracils, acting alongside conventional hydrogen bonds. Full article
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Open AccessArticle
Preparation and Single Crystal Structure Determination of the First Biobased Furan-Polydiacetylene Using Topochemical Polymerization
Crystals 2019, 9(9), 448; https://doi.org/10.3390/cryst9090448 - 29 Aug 2019
Abstract
Crystal structure elucidations of bio-based polymers provide invaluable data regarding structure–property relationships. In this work, we achieved synthesis and Single Crystal X-ray Diffraction (SCXRD) structural determination of a new furan-based polydiacetylene (PDA) derivative with carbamate (urethane) functionality. Firstly, diacetylene (DA) monomers were found [...] Read more.
Crystal structure elucidations of bio-based polymers provide invaluable data regarding structure–property relationships. In this work, we achieved synthesis and Single Crystal X-ray Diffraction (SCXRD) structural determination of a new furan-based polydiacetylene (PDA) derivative with carbamate (urethane) functionality. Firstly, diacetylene (DA) monomers were found to self-assemble in the crystalline state in such a way that the polymerization theoretically occurred in two different directions. Indeed, for both directions, geometrical parameters for the reactive alignment of DA are satisfied and closely related with the optimal geometrical parameters for DA topochemical polymerization (d(1) = 4.7–5.2 Å, d(2) ≤ 3.8 Å, θ ≈ 45°). However, within the axis of hydrogen bonds (HB), the self-assembling monomers display distances and angles (d(1) = 4.816 Å, d(2) = 3.822 Å, θ = 51°) that deviate more from the ideal values than those in the perpendicular direction (d(1) = 4.915Å, d(2) = 3.499Å, θ ≈ 45°). As expected from these observations, the thermal topochemical polymerization occurs in the direction perpendicular to the HB and the resulting PDA was characterized by SCXRD. Full article
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Open AccessArticle
Elucidation of the Structure of the 2-amino-3,5-Dibromochalcone Epoxides in Solution and Solid State
Crystals 2019, 9(6), 277; https://doi.org/10.3390/cryst9060277 - 28 May 2019
Cited by 1
Abstract
The conformation of the title compounds was determined in solution by 1H-NMR spectroscopy and in solid state by single-crystal X-ray diffraction (XRD) complemented with density functional theory. The compounds were found to exist exclusively in solution and solid state as trans-2-aminochalcone [...] Read more.
The conformation of the title compounds was determined in solution by 1H-NMR spectroscopy and in solid state by single-crystal X-ray diffraction (XRD) complemented with density functional theory. The compounds were found to exist exclusively in solution and solid state as trans-2-aminochalcone epoxides with strong intramolecular hydrogen bonding interaction between the amino and carbonyl groups. These 2-aminochalcone epoxides experienced a solvent effect in DMSO-d6, which resulted in an anomalous chemical shift for the α-hydrogen signal, presumably due to complexation of solute molecules with DMSO. The solute–solvent interaction would probably fix the trans conformation of epoxyketone such that α-H is more accessible to both aryl rings, and in turn, experience their combined anisotropic effect. Intermolecular interactions in the crystal structures were confirmed and quantified using the Hirshfeld surface analysis. Moreover, the trans stereochemistry of the α-epoxyketones facilitated direct one-pot sequential sulfuric acid-mediated ring opening and aryl migration to afford the corresponding 3-arylquinolin-4(1H)-ones (azaisoflavones). Full article
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Open AccessArticle
Substituent Effects in the Crystal Packing of Derivatives of 4′-Phenyl-2,2′:6′,2″-Terpyridine
Crystals 2019, 9(2), 110; https://doi.org/10.3390/cryst9020110 - 20 Feb 2019
Abstract
We report the preparation of a series of new 4′-substituted 2,2′:6′,2″-terpyridines: 4′-(3,5-dimethylphenyl)-2,2′:6′,2″-terpyridine (2), 4′-(3-fluoro-5-methylphenyl)-2,2′:6′,2″-terpyridine (3), 4′-(3,5-difluorophenyl)-2,2′:6′,2″-terpyridine (4), and 4′-(3,5- bis(trifluoromethyl)phenyl)-2,2′:6′,2″-terpyridine (5). The compounds have been characterized by mass spectrometry, solid-state IR spectroscopy and solution NMR [...] Read more.
We report the preparation of a series of new 4′-substituted 2,2′:6′,2″-terpyridines: 4′-(3,5-dimethylphenyl)-2,2′:6′,2″-terpyridine (2), 4′-(3-fluoro-5-methylphenyl)-2,2′:6′,2″-terpyridine (3), 4′-(3,5-difluorophenyl)-2,2′:6′,2″-terpyridine (4), and 4′-(3,5- bis(trifluoromethyl)phenyl)-2,2′:6′,2″-terpyridine (5). The compounds have been characterized by mass spectrometry, solid-state IR spectroscopy and solution NMR and absorption spectroscopies. The single-crystal X-ray diffraction structures of 3, 5 and 6·EtOH (6 = 4′-(3,5-bis(tert-butyl)phenyl)-2,2′:6′,2″-terpyridine) have been elucidated. The molecular structures of the compounds are unexceptional. Since 3 and 5 crystallize without lattice solvent, we are able to understand the influence of introducing substituents in the 4′-phenyl ring and compare the packing in the structures with that of the previously reported 4′-phenyl-2,2′:6′,2″-terpyridine (1). On going from 1 to 3, face-to-face π-stacking of pairs of 3-fluoro-5-methylphenyl rings contributes to a change in packing from a herringbone assembly in 1 with no ring π-stacking to a layer-like packing. The latter arises through a combination of π-stacking of aromatic rings and N…H–C hydrogen bonding. On going from 3 to 5, N…H–C and F…H–C hydrogen-bonding is dominant, supplemented by π-stacking interactions between pairs of pyridine rings. A comparison of the packing of molecules of 6 with that in 1, 3 and 5 is difficult because of the incorporation of solvent in 6·EtOH. Full article
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