Crystal and molecular structure of a crown-bridgedp-t-butyl-calix[4]arene (1:1) pyridine complex. Host-guest interaction model based on molecular mechanics analysis [1]

Andreetti, G. D.; Ori, O.; Ugozzoli, Franco; Alfieri, C.; Pochini, Andrea; Ungaro, Rocco

doi:10.1007/bf00660750

Cited by 63 publications

(21 citation statements)

References 16 publications

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“…These interactions are electrostatically reasonable, since the benzene carbons have partial negative charges, -0.115 e, and the methoxy methyl groups have charges of +0.25 e in the OPLS model (Table 1). This type of methyl-aryl interaction has also been noted recently in other host-guest systems (41,42). In the mutation from p-xylene to benzene, no water slipped into the cavity, though there often appears to be room for one water molecule.…”

Section: Consistent Withsupporting

confidence: 66%

Modeling the complexation of substituted benzenes by a cyclophane host in water.

Jorgensen

Nguyen

1993

Proc. Natl. Acad. Sci. U.S.A.

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Monte Carlo statistical mechanics simulations have been used to study the complexation of disubstituted benzenes by Diederich's octamethoxy tetraoxaparacyclophane host. Relative free energies of binding were obtained in water at 250C for benzene, p-xylene, p-cresol, p-dicyanobenzene, and hydroquinone from statistical perturbation theory. The computed results agree well with experimental data, including the binding affinity of benzene, which was determined after the calculations were completed. The computed structures for the complexes reveal details that are important for understanding the order of binding affinities. It is found that hydroquinone protrudes from one side of the complex and participates in hydrogen bonds between one hydroxyl group and two water molecules and in an intracomplex hydrogen bond between the other hydroxyl group and ether oxygens. The calculations also show a clear preference for binding p-cresol with the hydroxyl group hydrated rather than inside the host's cavity.The central role of intermolecular binding events in biochemistry and the potential for developing synthetic catalysts and novel materials have helped foster great experimental (1-5) and computational (6-19) interest in host-guest chemistry. The interplay between theory and experiment has been aided by the development of methodology that allows computation ofrelative and absolute free energies ofbinding (6,15,16) and by the ability of fluid simulations to provide exquisite structural details. Much computational effort has been directed at enzyme-ligand binding and the complexation of atomic ions by organic hosts (6-14), though complexes of neutral guests with organic hosts are now receiving increased attention (17-19). Water-soluble hosts that bind neutral guests are of particular interest as models of biological systems and as starting points for the design of nonenzymatic catalysts. Important contributions have been made in this area by many researchers, as reviewed by Diederich (4). The most common examples feature cyclodextrins and cyclophanes, which have relatively hydrophobic binding cylinders or slots. We have chosen to direct computational efforts at the cyclophanes in view oftheir potential structural diversity and the availability of experimental binding data for many systems. They also provide a rich venue for investigating the factors that control binding in water and the opportunity to complement the experimental studies by helping characterize the structures of the complexes, including specific interactions between host, guest, and water.Our first effort has been aimed at Diederich's octamethoxy tetraoxaparacyclophane, 1, which binds substituted benzenes in its slot-like cavity (20)(21)(22)

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Section: Consistent Withsupporting

confidence: 66%

Modeling the complexation of substituted benzenes by a cyclophane host in water.

Jorgensen

Nguyen

1993

Proc. Natl. Acad. Sci. U.S.A.

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“…13 They first suggested the importance of CH/p interaction in supramolecular chemistry on the basis of crystallographic data of various calix [4]arene complexes. [14][15][16][17] Sigel reported that certain ternary metal complexes are favoured in the folded conformation when at least one of the ligands is aromatic. 18 Okawa recognized the importance of CH/ p interaction in determining the configuration of coordination complexes.…”

Section: Motohiro Nishiomentioning

confidence: 99%

CH/? hydrogen bonds in crystals

Nishio¹

2004

CrystEngComm

1,389

781

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The nature and characteristics of the CH/p interaction are discussed by comparison with other weak molecular forces such as the CH/O and OH/p interaction. The CH/p interaction is a kind of hydrogen bond operating between a soft acid CH and a soft base p-system (double and triple bonds, C 6 and C 5 aromatic rings, heteroaromatics, convex surfaces of fullerenes and nanotubes). The consequences of CH/p hydrogen bonds in supramolecular chemistry are reviewed on grounds of recent crystallographic findings and database analyses. The topics include intramolecular interactions, crystal packing (organic and organometallic compounds), host/ guest complexes (cavity-type inclusion compounds of cyclodextrins and synthetic macrocyclic hosts such as calixarenes, catenanes, rotaxanes and pseudorotaxanes), lattice-inclusion type clathrates (including liquid crystals, porphyrin derivatives, cyclopentadienyl compounds and C 60 fullerenes), enantioselective clathrate formation, catalytic enantioface discriminating reactions and solid-state photoreaction. The implications of the CH/p concept for crystal engineering and drug design are evident.

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“…The presence of the tert-butyl groups appears to be essential for the precipitation of the complex, 10 revealing that a crucial role could be played by a delocalizative interaction between the nonbonded hydrogen atoms of CH 3 and the C 60 carbon atoms bearing electrons. 12 Although the energy involved in this hydrogen-bond-like CHinteraction is small, cooperativity can occur in supramolecular systems, enhancing its role during the formation of the complex.…”

Section: ͓S0163-1829͑97͒08009-0͔mentioning

confidence: 99%

“…Andreetti et al 12 have pointed out the importance of the CHinteraction between the CH groups of the host and the included aromatic guest molecules. Direct experimental evidence that such an elusive interaction exists was, however, not available up to now.…”

Section: ͓S0163-1829͑97͒08009-0͔mentioning

confidence: 99%

Vibrational spectrum ofC60sin the p-tert-butylcalix[8]arene(1:1)C60
Paci
¹
,
Amoretti
²
,
Arduini
³

et al. 1997
Phys. Rev. B
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We report the results of Raman, infrared, and inelastic neutron scattering investigations of the vibrational spectrum of the complex p-tert-butylcalix͓8͔arene͑1:1͒fullerene, a system with almost isolated C 60 molecules confined inside neutral cages. All the internal optical-active modes of the C 60 guest have been identified, and further modes which can be attributed to C 60 intramolecular vibrations appear in the neutron scattering function. A comparison with the vibrational spectrum of empty p-tert-butylcalix͓8͔arene indicates that the hostguest interaction is very weak. As solid-state effects are also practically suppressed, the investigated complex gives the unique opportunity to study almost free fullerene balls confined in the solid state.A huge number of theoretical and experimental studies followed the discovery of the new fullerene allotropes of carbon. Much of the interest has been focused on the dynamical properties of C 60 , and a comprehensive picture of the vibrational behavior has been obtained by a combination of neutron, Raman, and infrared scattering experiments. 1-6 However, it is not yet clear to what extent the presence of solid-state effects complicates the comparison of the experimental results with quantum-mechanical calculations performed for isolated C 60 molecules. The splitting of the degenerate molecular modes deserves further investigation as well, being not only a consequence of the crystal field, 6 but also the result of 12 C/ 13 C isotopic effects 7 and of merohedral orientational disorder in crystalline C 60 . 8 Here we present light and neutron spectroscopy results which reveal the existence of a unique opportunity of studying the behavior of fullerene in a quasifree environment. Actually, the experimental findings show that the C 60 molecules, confined in the solid-state complex with p-tert-butylcalix͓8͔arene, are almost isolated.Calixarenes are cup-shaped macrocyclic phenolic oligomers which find increasing applications as building blocks of receptors for the selective complexation of alkali and alkaline-based metal cations. Moreover, for their ability to form inclusion complexes with neutral organic molecules, calixarenes have been the subject of a number of investigations in the framework of the host-guest or supramolecular chemistry. 9 Among this class of synthetic matrices, the p-tert-butylcalix͓n͔arene ͑where nϭ8 refers to the number of phenolic units͒, is able to include the fullerene molecule, and recently a ͑1:1͒ complex of p-tert-butylcalix͓8͔arene with C 60 has been obtained. 10,11 This is an important breakthrough in fullerene chemistry, offering an economic means of C 60 purification and providing, on the other hand, an interesting inclusion system for the study of the C 60 dynamics. Actually, infrared ͑IR͒, visible, and ultraviolet spectra, together with 13 C NMR results, strongly indicate that the C 60 is weakly bound to the upper edge of the calix͓8͔arene cavity ͑Fig. 1͒ and that interactions among the fullerene molecules PHYSICAL

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Crystal and molecular structure of a crown-bridgedp-t-butyl-calix[4]arene (1:1) pyridine complex. Host-guest interaction model based on molecular mechanics analysis [1]

Cited by 63 publications

References 16 publications

Modeling the complexation of substituted benzenes by a cyclophane host in water.

Modeling the complexation of substituted benzenes by a cyclophane host in water.

CH/? hydrogen bonds in crystals

Vibrational spectrum ofC60sin the p-tert-butylcalix[8]arene(1:1)C60
Paci
¹
,
Amoretti
²
,
Arduini
³

et al. 1997
Phys. Rev. B
Self Cite
25
1
15
0
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Crystal and molecular structure of a crown-bridgedp-t-butyl-calix[4]arene (1:1) pyridine complex. Host-guest interaction model based on molecular mechanics analysis [1]

Cited by 63 publications

References 16 publications

Modeling the complexation of substituted benzenes by a cyclophane host in water.

Modeling the complexation of substituted benzenes by a cyclophane host in water.

CH/? hydrogen bonds in crystals

Vibrational spectrum ofC60sin the p-tert-butylcalix[8]arene(1:1)C60Paci1, Amoretti2, Arduini3 et al. 1997Phys. Rev. BSelf Cite251150View full textAdd to dashboardCite

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Vibrational spectrum ofC60sin the p-tert-butylcalix[8]arene(1:1)C60
Paci
¹
,
Amoretti
²
,
Arduini
³

et al. 1997
Phys. Rev. B
Self Cite
25
1
15
0
View full text Add to dashboard Cite