The crystal structure of the molecular complex of 4:4'-dinitrodiphenyl with diphenyl

Niekerk, J. N. van; Saunder, D. H.

doi:10.1107/s0365110x48000107

Cited by 24 publications

(5 citation statements)

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“…The sensitive balance between these factors is reflected in available experimental data of model systems such as 2,2‘- and 4,4‘-bipyridine which are known to be planar in the crystalline state but twisted in the gaseous phase as well as in benzene solution (>20° and 37.2°, respectively 47 ). Furthermore, X-ray crystallographic data of pyridinium ylides 42 and pyridinium cations 13a show coplanar as well as twisted pyridinium rings depending on the substitution pattern.…”

Section: Resultsmentioning

confidence: 99%

Charged and Betainic Nucleobases. On Syntheses and Properties of First Mesomeric Uracilylbetaines, Uracilates, and Novel Uracilium Salts

Schmidt

Kindermann

1997

J. Org. Chem.

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Nucleophilic heteroaromatic substitution of DMAP and 1-methylimidazole on the 6-chlorouracil 1 gave the uracilyl hetarenium salts 2 and 4, respectively. Depending on the nucleophile, the substitution could be catalyzed by interception of the leaving group either with sodium tetraphenylborate or with antimony pentachloride in a non-coordinating solvent. Catalysis with other Lewis acids failed due to the formation of stable coordination compounds 3. Surprisingly, Finkelsteintype reaction conditions provide an efficient approach to the imidazolium iodide 4. Depending on the reaction conditions, treatment of the 6-chlorouracil 5 with DMAP resulted in the formation of the pyridinium uracilate 6, the uracilyl pyridinium chloride 7a, and the novel pyridinium-uracilate 8 which is a cross-conjugated mesomeric betaine (CCMB). Alkylation of the mesomeric betaine 8 with 1,2-dichloroethane/SbCl 5 gave the biscation 9. Analogously, 1-methylimidazole or 2,4,6trimethylpyridine as nucleophiles formed the salts 10a and 12, respectively, and the imidazoliumuracilate 11. This is the first representative of a cross-conjugated heterocyclic mesomeric betaine isoconjugate with odd nonalternant hydrocarbon anions. PM3 calculations were performed on the cation 2 and on the mesomeric betaine 8. Whereas the cation 2 was found to have an essentially perpendicular torsional angle Φ around the CN + bond linking the uracil and the pyridinium units, the mesomeric betaine 8 adopts a nearly planar conformation, thus allowing stabilizing π interactions. Accordingly, upon rotation about the CN + bond, the expected maxima were found at essentially perpendicular conformations. Due to the balance between three effects which act in opposite directions, (i) stabilizing p overlap, (ii) N(8)/2-H attractive interaction, and (iii) steric repulsion between 6-H and 12-H, two additional small minima were surprisingly found at Φ ) 36.6°and 219.3°. The charge separation in the ground state of the mesomeric betaine 11, and the ground-state ion-pair complexes of the hetarenium iodides 2d, 4, 7c, and 10b were confirmed by the effect of negative solvatochromism. X

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Section: Resultsmentioning

confidence: 99%

Charged and Betainic Nucleobases. On Syntheses and Properties of First Mesomeric Uracilylbetaines, Uracilates, and Novel Uracilium Salts

Schmidt

Kindermann

1997

J. Org. Chem.

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“…At least one of these compounds is molecular (the cocrystal former) and forms supramolecular synthons(s) with the remaining component(s) . If one uses this definition then the first cocrystals were reported in the 1800s, and they have had various terms applied to them: addition compounds, organic molecular compounds, complexes and heteromolecular crystals. − Cocrystals are also distinct from solvates, salts, and inclusion compounds if one employs this definition. APIs are a natural target for cocrystals since the solid state chemistry of APIs represents an area of scientific, commercial, regulatory and legal interest .…”

Section: Introductionmentioning

confidence: 99%

Hierarchy of Supramolecular Synthons: Persistent Carboxylic Acid···Pyridine Hydrogen Bonds in Cocrystals That also Contain a Hydroxyl Moiety

Shattock

Arora

Vishweshwar

et al. 2008

Crystal Growth & Design

442

284

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A Cambridge Structural Database (CSD) analysis was conducted in order to evaluate the hierarchy of supramolecular heterosynthons that involve two of the most relevant functional groups in the context of active pharmaceutical ingredients, carboxylic acids and alcohols, in competitive environments. The study revealed that 34% of the 5690 molecular carboxylic acid entries and 26% of the 25 035 molecular alcohol entries form supramolecular homosynthons, whereas the remaining entries form supramolecular heterosynthons with other functional groups, in particular Narom, CONH2, C−O−C, CO, and chloride anions. Further refinement of this raw data revealed the following: 98% occurrence of the COOH···Narom supramolecular heterosynthon in the 126 crystal structures that contain acid and pyridine moieties in the absence of other hydrogen bond donors or acceptors; and 78% occurrence of the OH···Narom supramolecular heterosynthon in 228 crystal structures that contain hydroxyl and pyridine moieties (excluding intramolecular hydrogen bonding). Such high frequencies indicate that these supramolecular heterosynthons are strongly favored over their respective COOH···COOH and OH···OH supramolecular homosynthons. However, the CSD does not contain enough information to evaluate the predictability of even common supramolecular heterosynthons in the presence of competing hydrogen bonding moieties; for example, there are only 15 entries when -COOH, -OH, and Narom moieties are present exclusively (no other hydrogen bond donors and acceptors groups) in a molecule. We have addressed the competition between the COOH···Narom and the OH···Narom supramolecular heterosynthons by analyzing these 15 entries in CSD and characterizing 15 new compounds (cocrystals 1−13; salts 14 and 15) that are composed of cocrystal formers which contain a permutation of -COOH, -OH and Narom functional groups. Analysis of this group of compounds reveals that supramolecular heterosynthons are favored over the respective supramolecular homosynthons. We also address the methodologies that can be used to prepare 1−15 in the context of solvent evaporation, solvent-drop grinding, and slurrying.

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“…46,47 We 9-11 and others 48 have operated under the assumption that a cocrystal is a multiple component crystal in which all components when pure are solid under ambient conditions. Such compounds have been described using various terms, e.g., molecular compounds, 49 organic molecular compounds, 50 addition compounds, 51 molecular complexes, 52 solid-state complexes, 53 or heteromolecular crystals. 54 Although such compounds are long known, as exemplified by the prototypal cocrystal quinhydrone (1844), 55 cocrystals are not as widely studied as single-component crystals or solvates.…”

Section: Introductionmentioning

confidence: 99%

Hierarchy of Supramolecular Synthons: Persistent Hydroxyl···Pyridine Hydrogen Bonds in Cocrystals That Contain a Cyano Acceptor

et al. 2007

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An analysis of the Cambridge Structural Database reveals >99% occurrence of the hydroxyl...pyridine supramolecular heterosynthon in crystal structures that contain hydroxyl and pyridine moieties in the absence of other hydrogen-bonding moieties. The occurrence of the hydroxyl...cyano supramolecular heterosynthon in crystal structures that contain hydroxyl and cyano moieties is ca. 77%. Such high frequencies indicate that these heterosynthons are strongly favored over the competing hydroxyl...hydroxyl supramolecular homosynthon. However, the CSD does not contain enough information to evaluate which supramolecular heterosynthon prevails when only OH, pyridine, and CN moieties are present in a crystal structure. We have addressed the competition between the hydroxyl...pyridine and the hydroxyl...cyano supramolecular heterosynthons by characterizing a series of 17 cocrystals that are composed of cocrystal formers which contain a permutation of OH, pyridine, and CN functional groups. Structural analysis reveals that all cocrystals are sustained by the hydroxyl...pyridine heterosynthon.

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The crystal structure of the molecular complex of 4:4'-dinitrodiphenyl with diphenyl

Cited by 24 publications

References 0 publications

Charged and Betainic Nucleobases. On Syntheses and Properties of First Mesomeric Uracilylbetaines, Uracilates, and Novel Uracilium Salts

Charged and Betainic Nucleobases. On Syntheses and Properties of First Mesomeric Uracilylbetaines, Uracilates, and Novel Uracilium Salts

Hierarchy of Supramolecular Synthons: Persistent Carboxylic Acid···Pyridine Hydrogen Bonds in Cocrystals That also Contain a Hydroxyl Moiety

Hierarchy of Supramolecular Synthons: Persistent Hydroxyl···Pyridine Hydrogen Bonds in Cocrystals That Contain a Cyano Acceptor

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