A Classical Example of a Disappearing Polymorph and the Shortest Intermolecular H⋅⋅⋅H Separation Ever Found in an Organic Crystal Structure

Bombicz, Petra; Czugler, Mátyás; Tellgren, R.; Kàlmán, Alajos

doi:10.1002/anie.200219504

Cited by 28 publications

(6 citation statements)

References 37 publications

(52 reference statements)

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“…Unusually short contacts are rare but not unknown. For example, a very short but real contact of = 1.02 Å is observed in the crystal structure of pyrene-II, and to our knowledge the shortest intermolecular H···H contact in an organic crystal structure is that of the unstable polymorph of 1,2,3,5-tetra- O -acetyl- β - d -ribofuranose, with a H···H distance of 1.949(7) Å . The existence of these short contacts, usually thought to be repulsive in nature, appears to be in accordance with the recent concept of H···H interactions as bonding and stabilizing interactions in a crystal structure …”

Section: Resultssupporting

confidence: 85%

Comparison of Polymorphic Molecular Crystal Structures through Hirshfeld Surface Analysis

McKinnon

Fabbiani

Spackman

2007

Crystal Growth & Design

306

200

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Graphical tools based on Hirshfeld surfaces and two-dimensional (2D) fingerprint plots are shown to be valuable for visualizing and analyzing intermolecular interactions in polymorphs of molecular crystals and make the task of polymorph comparison easier and considerably faster. This is the direct result of the underlying principle behind the Hirshfeld surface, which embraces a “whole of structure” view of intermolecular interactions, rather than concentrating exclusively on assumed important (i.e., short) interactions. The subtle relationships between polymorphs of tetrathiafulvalene and p-dichlorobenzene are more easily discernible through comparison of Hirshfeld surfaces and fingerprint plots, rather than solely through conventional structure viewing, and differences and similarities among clearly distinct polymorphs of oxalic acid, terephthalic acid, and p-dichlorobenzene more readily emerge and can be easily catalogued in terms of specific atom···atom interaction types. Conformational polymorphism makes the comparisons more challenging, and Hirshfeld surfaces provide sufficient information for piracetam, while for ROY (5-methyl-2-((2-nitrophenyl)amino)-3-thiophenecarbonitrile, nicknamed ROY due to its red, orange, and yellow crystal forms) fingerprint plots are preferred, summarizing the major features of each crystal structure in a single, colored 2D plot. In addition to the successful applications to polymorph discrimination, improvements to the Hirshfeld surface approach are identified, the most notable being the breakdown of 2D fingerprint plots into specific atom···atom contacts in the crystal.

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Section: Resultssupporting

confidence: 85%

Comparison of Polymorphic Molecular Crystal Structures through Hirshfeld Surface Analysis

McKinnon

Fabbiani

Spackman

2007

Crystal Growth & Design

306

200

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“…However, they are related by a center of symmetry, and so their corresponding H-atoms are oriented either face to face (that is, angle, O−H···H 177°) or away from each other and are not considered hydrogen-bonded. The H···H separation of 1.144 Å is, however, shorter compared to the shortest intermolecular H···H separation (1.949 Å) found in the polymorph A of 1,2,3,5-tetra- O -acetyl-β- d -ribofuranose …”

Section: Resultsmentioning

confidence: 62%

Mn(II) Staircase Structures Stitched by Water Clusters to a 3D Metal-Organic Open Framework: X-ray Structural and Magnetic Studies

et al. 2005

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4-Hydroxypyridine-2,6-dicarboxylic acid (chelidamic acid, cdaH2) reacts with Mn(OAc)2 x 4H2O to form a 1D staircase structure with dimeric Mn(II) units connected by water clusters to form a 3D framework, {[Mn2(cda)2 x 4H2O] x 4H2O}n, 1, in aqueous pyridine at room temperature. The compound crystallizes in the triclinic space group P1 with a = 9.495(3), b =10.733(5), c = 11.065(4) A, alpha = 87.42(5), beta = 74.14(5), gamma = 80.07(2) degrees, U = 1068.5(9) A3, Z = 2, rho(calcd) = 1.915 g cm(-3), T = 100 K, mu = 1.28 mm(-1), R1 = 0.0453 (I > 2sigma(I)), wR2 = 0.1046, GOOF = 1.282. Upon removal of the water molecules by heating, the 3D structure breaks down. Thermogravimetric analysis, infrared, X-ray powder diffraction studies, and X-ray crystallography were performed to characterize this compound. Since the coordination polymer has diaqua-bridged Mn(II) centers, it was subjected to variable-temperature magnetic studies.

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“…After isolation of form 3, we were unable to recover transient phase 2 under different experimental conditions, such as solvents of crystallization, new glassware, and change to another laboratory. Form 2 belongs to the anecdotal category of disappearing polymorphs . Interconversion and stability of forms 1−3 was examined by differential scanning calorimetry (Figure ).…”

Section: Resultsmentioning

confidence: 99%

Kinetic and Thermodynamic Conformational Polymorphs of Bis(p-tolyl) Ketone p-Tosylhydrazone: The Curtin−Hammett Principle in Crystallization

Roy

Nangia

2007

Crystal Growth & Design

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Bis(p-tolyl) ketone p-tosylhydrazone (2) crystallized as three conformational polymorphs, forms 1-3, under different conditions. The crystal structure of form 1 has an N-H‚‚‚OdS dimer synthon, but forms 2 and 3 have no strong hydrogen bonds even though the molecule contains an SO 2 NH group. Polymorphs 1 and 3 are assigned as kinetic and thermodynamic forms on the basis of the criteria of lower energy, higher melting point, and higher density for the latter modification. Calculation of both intramolecular (E conf ) and intermolecular energy (U latt ) gave a crystal energy difference (∆E total ) of 2.54 kcal mol -1 between forms 1 and 3, whereas metastable and disappearing form 2 has much a higher energy of 8.71 kcal mol -1 . Sulfonamide 2 is a rare example of a polymorph cluster wherein strong hydrogen bonds stabilize kinetic form 1 whereas thermodynamic polymorph 2 has excellent close packing but no hydrogen bonds. A Curtin-Hammett energy profile for the crystallization of conformational polymorphs 1 and 3 is proposed that is consistent with structural, thermochemical, and computational data. Hydrogen bonding in tolyl compound 2 is compared with other benzophenone hydrazones varying at the para-position (e.g., H, F, Cl, Br). The bimolecular N-H‚‚‚OdS dimer is present in crystal structures 3-6 as well as in the CH 2 Cl 2 solvate of 2 and benzene solvates of chloro 5 and bromo 6 hydrazones.

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A Classical Example of a Disappearing Polymorph and the Shortest Intermolecular H⋅⋅⋅H Separation Ever Found in an Organic Crystal Structure

Cited by 28 publications

References 37 publications

Comparison of Polymorphic Molecular Crystal Structures through Hirshfeld Surface Analysis

Comparison of Polymorphic Molecular Crystal Structures through Hirshfeld Surface Analysis

Mn(II) Staircase Structures Stitched by Water Clusters to a 3D Metal-Organic Open Framework: X-ray Structural and Magnetic Studies

Kinetic and Thermodynamic Conformational Polymorphs of Bis(p-tolyl) Ketone p-Tosylhydrazone: The Curtin−Hammett Principle in Crystallization

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