Weak Intermolecular Forces, but High Melting Points

Gao, Jun; Djaidi, Djamal; Marjo, Christopher E.; Bhadbhade, Mohan; Ung, Alison T.; Bishop, Roger

doi:10.1071/ch16565

Cited by 6 publications

(5 citation statements)

References 30 publications

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“…Our synthetic target was the new hexabromodiquinoline 8 , which is a positional isomer of an earlier compound 5 that showed an exclusive preference for including aromatic hydrocarbon guests . The racemic diquinoline derivative 6 was subjected to electrophilic aromatic bromination following the procedure originally devised for quinoline by de la Mare, and much later applied by us to bridged diquinoline derivatives. , The resulting tetrabromodiquinoline 7 then underwent Wohl–Ziegler benzylic bromination , with N -bromosuccinimide (NBS) to produce the hexabromodiquinoline 8 . The yields of these reactions were modest and lower than those obtained for earlier diquinoline derivatives.…”

Section: Resultsmentioning

confidence: 99%

Multimolecular Weak-Force Tectons and Their Alternative Clathrate Forms

Gao

Bhadbhade

Bishop

2020

Crystal Growth & Design

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diquinoline 8 forms clathrate compounds on crystallization from benzene, acetone, or diethyl ether. Their crystal structures are analyzed in crystal engineering terms. Molecules of 8 form robust dimers, containing swivel angles around 110°, and assembled through a combination of seven intermolecular attractions. Two enantiomeric dimers assemble around an inversion center by means of eight further attractions. A cyclic R 2 2 (8) motif utilizing −CBr−H•••N weak hydrogen bonds is the key construction element used in both the intra-and interdimer assembly. These resulting tetramers are multimolecular tectons that generate the host lattice on propagation. In contrast to the usual unimolecular model, each multimolecular tecton is constructed from 4 molecules and 22 intermolecular attractions. All three clathrates involve crystallographically independent molecules, and the latter two crystals each employ two isomeric multimolecular tectons. The diethyl ether crystal contains a further independent host molecule that shores up its guest-containing substructure.

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Section: Resultsmentioning

confidence: 99%

Multimolecular Weak-Force Tectons and Their Alternative Clathrate Forms

Gao

Bhadbhade

Bishop

2020

Crystal Growth & Design

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“…Perhaps the most striking case is the crystal structure of racemic diquinoline 7 , in which considerable enantiomer ordering has taken place to produce homochiral layers. The fully eclipsed stacked columns of homochiral 7 require endo,exo -interactions with parallel aromatic long axes (swivel angle 180°) …”

Section: Results and Discussionmentioning

confidence: 99%

“…Crystal Structure of (6) 4 •(benzene) 3 . 40 The inclusion compound (6) 4 •(benzene) 3 contains two independent molecules of 6 (A and B) and their enantiomers (A* and B*). Pairs of host molecules (A/B* and A*/B) associate by means of a Type I endo,endo-facial π•••π interaction K with a swivel angle of 104.9°(Figure 12, upper).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Swivel and Tilt Interactions: Directional Change in Aromatic π···π Crystal Packing

Bishop

Bhadbhade

Scudder

et al. 2018

Crystal Growth & Design

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Offset interfacial π•••π overlap between two aromatic groups of unequal length and breadth often occurs with unidirectional alignment of their molecular long axes. However, π•••π interaction can also occur with directional change. Analysis of diquinoline crystal structure data reveals π•••π swivel angles from 0°(antiparallel alignment) through to 180°( parallel long axes). Swivel angles in the range 0−35°are commonplace and are compatible with the formation of linear and layer assemblies. Larger swivel angle values are less frequent, and their appearance is encouraged through competition with other weak attractive forces. These higher angular values are associated with formation of zigzag chains, corrugated layers, unusual building blocks, homochiral assemblies, and other less common crystal packing modes. Directional change also occurs in structures where the planes of the interacting π-systems are nonparallel, and the consequences of these tilt angles are described. The principles described herein are applicable to aromatic systems in general.

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“…The locking of molecules in the herringbone pattern of C-HÁ Á Á contacts between the naphthalene groupings and the the adjacent thiophene rings may explain the significantly higher melting point of (3) (441 K) compared to (4) (410 K). Although these interactions are not considered to be strong, this herringbone pattern of interlocking molecules is known to result in a higher melting point in aromatic systems with a similar V-shaped geometry (Gao et al, 2017).…”

Section: Supramolecular Featuresmentioning

confidence: 99%

Structure of racemic duloxetine hydrochloride

et al. 2023

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Duloxetine hydrochloride (trade name Cymbalta) is marketed as a single enantiomer (S)-N-methyl-3-(naphthalen-1-yloxy)-3-(thiophen-2-yl)propylaminium chloride, C18H20NOS+·Cl−, which is twice as effective as the (R)-enantiomer in serotonin uptake. Here, we report the crystal structure of duloxetine hydrochloride in its racemic form (space group Pna21), where it shows significant differences in the molecular conformation and packing in its extended structure compared to the previously reported (S)-enantiomer crystal structure. Molecules of this type, comprising aromatic groups with a single side chain terminated in a protonated secondary amine, are commonly found in active antidepressants. A Cambridge Structural Database survey of molecules with these features reveals a strong correlation between side-chain conformation and the crystal packing: an extended side chain leads to molecules packed into separated layers of hydrophobic and ionic hydrophilic phases. By comparison, molecules with bent side chains, such as racemic duloxetine hydrochloride, lead to crystal-packing motifs where an ionic hydrophilic phase is encapsulated within a hydrophobic shell.

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Weak Intermolecular Forces, but High Melting Points

Abstract: Figure S1. ORTEP diagram showing the crystallographic numbering used for the crystal structure of 4. Figures S2, S3 and S4 depicting aspects of the crystal structure of 2.

Cited by 6 publications

References 30 publications

Multimolecular Weak-Force Tectons and Their Alternative Clathrate Forms

Multimolecular Weak-Force Tectons and Their Alternative Clathrate Forms

Swivel and Tilt Interactions: Directional Change in Aromatic π···π Crystal Packing

Structure of racemic duloxetine hydrochloride

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