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Crystallographic observation of 'induced fit' in a cryptophane host-guest model system.

Taratula O, Hill PA, Khan NS, Carroll PJ, Dmochowski IJ - Nat Commun (2010)

Bottom Line: Cryptophane-A, comprised of two cyclotriguaiacylenes joined by three ethylene linkers, is a prototypal organic host molecule that binds reversibly to neutral small molecules via London forces.Of note are trifunctionalized, water-soluble cryptophane-A derivatives, which exhibit exceptional affinity for xenon in aqueous solution.Cryptophane internal volume varied by more than 20% across this series, which exemplifies 'induced fit' in a model host-guest system.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104, USA.

ABSTRACT
Cryptophane-A, comprised of two cyclotriguaiacylenes joined by three ethylene linkers, is a prototypal organic host molecule that binds reversibly to neutral small molecules via London forces. Of note are trifunctionalized, water-soluble cryptophane-A derivatives, which exhibit exceptional affinity for xenon in aqueous solution. In this paper, we report high-resolution X-ray structures of cryptophane-A and trifunctionalized derivatives in crown-crown and crown-saddle conformations, as well as in complexes with water, methanol, xenon or chloroform. Cryptophane internal volume varied by more than 20% across this series, which exemplifies 'induced fit' in a model host-guest system.

No MeSH data available.


Related in: MedlinePlus

X-ray crystal structures of cryptophanes and inclusion complexes in side view. (a) Cryptophane-A with Xe, and b, with water, oxygen shaded red; both in CC conformation. (c) Tripropargyl cryptophane (1), with Xe, and d, partially occupied; both in CC conformation. (e) Triallyl cryptophane (2),  with Xe, in CC conformation. Xe atom is shaded blue; and f, collapsed, in CS conformation.
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f2: X-ray crystal structures of cryptophanes and inclusion complexes in side view. (a) Cryptophane-A with Xe, and b, with water, oxygen shaded red; both in CC conformation. (c) Tripropargyl cryptophane (1), with Xe, and d, partially occupied; both in CC conformation. (e) Triallyl cryptophane (2), with Xe, in CC conformation. Xe atom is shaded blue; and f, collapsed, in CS conformation.

Mentions: For crystallization of cryptophane–guest complexes, it was necessary to avoid solvents that compete for binding inside the cryptophane cavity. Fluorobenzene is a sterically bulky solvent that adequately solubilizes 1 and 2 to allow for crystal growth by vapour diffusion of diethyl ether or n-pentane. Cryptophane-A, 1 and 2 as racemic mixtures cocrystallized with xenon exhibited the CC conformation (Fig. 2a,c,e). Moreover, in the absence of suitable guests, the crystal structure of 1 revealed cryptophane in the CC conformation (Fig. 2d), in agreement with solution 1H NMR data. Either without guests or with xenon, 1 crystallized in the triclinic space group P1. The chirality of cryptophane-A arises from the anti relationship of the methoxy groups relative to the ethylene oxide bridges, as was also observed in previous cryptophane X-ray structures611.


Crystallographic observation of 'induced fit' in a cryptophane host-guest model system.

Taratula O, Hill PA, Khan NS, Carroll PJ, Dmochowski IJ - Nat Commun (2010)

X-ray crystal structures of cryptophanes and inclusion complexes in side view. (a) Cryptophane-A with Xe, and b, with water, oxygen shaded red; both in CC conformation. (c) Tripropargyl cryptophane (1), with Xe, and d, partially occupied; both in CC conformation. (e) Triallyl cryptophane (2),  with Xe, in CC conformation. Xe atom is shaded blue; and f, collapsed, in CS conformation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3105606&req=5

f2: X-ray crystal structures of cryptophanes and inclusion complexes in side view. (a) Cryptophane-A with Xe, and b, with water, oxygen shaded red; both in CC conformation. (c) Tripropargyl cryptophane (1), with Xe, and d, partially occupied; both in CC conformation. (e) Triallyl cryptophane (2), with Xe, in CC conformation. Xe atom is shaded blue; and f, collapsed, in CS conformation.
Mentions: For crystallization of cryptophane–guest complexes, it was necessary to avoid solvents that compete for binding inside the cryptophane cavity. Fluorobenzene is a sterically bulky solvent that adequately solubilizes 1 and 2 to allow for crystal growth by vapour diffusion of diethyl ether or n-pentane. Cryptophane-A, 1 and 2 as racemic mixtures cocrystallized with xenon exhibited the CC conformation (Fig. 2a,c,e). Moreover, in the absence of suitable guests, the crystal structure of 1 revealed cryptophane in the CC conformation (Fig. 2d), in agreement with solution 1H NMR data. Either without guests or with xenon, 1 crystallized in the triclinic space group P1. The chirality of cryptophane-A arises from the anti relationship of the methoxy groups relative to the ethylene oxide bridges, as was also observed in previous cryptophane X-ray structures611.

Bottom Line: Cryptophane-A, comprised of two cyclotriguaiacylenes joined by three ethylene linkers, is a prototypal organic host molecule that binds reversibly to neutral small molecules via London forces.Of note are trifunctionalized, water-soluble cryptophane-A derivatives, which exhibit exceptional affinity for xenon in aqueous solution.Cryptophane internal volume varied by more than 20% across this series, which exemplifies 'induced fit' in a model host-guest system.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104, USA.

ABSTRACT
Cryptophane-A, comprised of two cyclotriguaiacylenes joined by three ethylene linkers, is a prototypal organic host molecule that binds reversibly to neutral small molecules via London forces. Of note are trifunctionalized, water-soluble cryptophane-A derivatives, which exhibit exceptional affinity for xenon in aqueous solution. In this paper, we report high-resolution X-ray structures of cryptophane-A and trifunctionalized derivatives in crown-crown and crown-saddle conformations, as well as in complexes with water, methanol, xenon or chloroform. Cryptophane internal volume varied by more than 20% across this series, which exemplifies 'induced fit' in a model host-guest system.

No MeSH data available.


Related in: MedlinePlus