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Host Cavity (host + cavity)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

Symmetric Stretching Vibration of CH4 in Clathrate Hydrate Structures

CHEMPHYSCHEM, Issue 14 2010
Dr. Hiroshi Ohno
Movers and shakers: Vibrational states of CH4 molecules encaged in three clathrate hydrate structures are studied (see picture). Guest methane distribution in the structure-H 512 and 435663 host cavities is revealed for the first time. Raman profiles of the CH4 vibration are dependent not only on types of water cages, but also on clathrate structures (guest compositions), suggesting distinctive differences in molecular interactions between the three hydrate systems. [source]

Encapsulation and Stabilization of Reactive Aromatic Diazonium Ions and the Tropylium Ion Within a Supramolecular Host

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 24 2004
Julia L. Brumaghim
Abstract Supramolecular assemblies with internal cavities are being developed as nanoscale reaction vessels to protect or modify the reactivity of guest species through encapsulation. Diazonium cations and the tropylium cation were examined for their ability to encapsulate in the tetrahedral [Ga4L6]12, supramolecular assembly. The 4-(diethylamino)benzenediazonium cation 1 readily formed a 1:1 host,guest complex with this assembly, and this encapsulation prevented 1 from reacting with 2,4-pentanedione in D2O. The tropylium cation also formed a 1:1 host,guest complex with the [Ga4L6]12, assembly, greatly slowing its decomposition in D2O. Encapsulation in the protected environment of this host cavity alters the reactivity of these guest molecules, giving them greater stability. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

Mechanism of Selective and Unselective Enclathration by a Host Compound Possessing Open, Flexible Host Frameworks

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 13 2003
Kazunori Nakano
Abstract Molecular recognition of o -, m -, and p -xylenes (oX, mX, and pX) through enclathration of cholic acid (CA) is described. All of the xylenes give lattice inclusion crystals with CA, and crystallographic studies reveal that they are included in different open host frameworks. In particular, oX has two polymorphs, depending on the recrystallization temperatures. Competitive recrystallization from mixtures of xylenes resulted in selective enclathrations and the formation of racemic mixed crystals. In the presence of an equimolar amount of oX, CA selectively includes mX or pX in the host frameworks, which are identical to those obtained from the pure mX or pX, respectively. The low affinity of oX is explained in terms of a lower stability of CA·oX than of the other two complexes, as judged from the low PCcavity, the volume ratio of the guest compound to the host cavity. Meanwhile, mixtures of mX and pX yield inclusion crystals that accommodate both of the guests. These have the same open host framework as obtained from pure mX, and the guest components are disordered statically in the host cavity. The ratios of the xylene mixtures in the single crystals are similar to those in the original recrystallization mixtures, and also in the bulk crystals, indicating that CA forms mixed crystals of mX and pX. This non-selectivity is attributed to the similar stabilities of CA·mX and CA·pX, according to the moderate PCcavity. The inclusion behavior of CA from mixtures of xylenes is quite similar to chiral recognition by diastereomer-salt methods. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

Spectroscopic Study on Interaction of , -Cyclodextrin with Triprolidine Hydrochloride

CHINESE JOURNAL OF CHEMISTRY, Issue 5 2006
Syed Mashhood Ali
Abstract The complexation of triprolidine hydrochloride (TRP) and , -cyclodextrin (, -CD) in deuterium oxide was investigated by 400 MHz 1H NMR spectroscopy. The 800 MHz 2D ROESY data revealed that two 1:1 and one 2:1 , -CD-TRP inclusion complexes were formed. Both aromatic moieties (p -tolyl and pyridyl ring) has entered into the , -CD cavity, confirming the existence of two different equilibria for 1:1 inclusion complexes in which p -tolyl ring of the guest is more tightly held by the host cavity. The ROE intermolecular interactions provided the plausible structures of these 1:1 and 2:1 stoichiometric inclusion complexes of , -CD-triprolidine hydrochloride in solution. [source]

Chiral recognition of dipeptide methyl esters by an anionic ,-cyclodextrin

CHIRALITY, Issue 8 2001
Koji Kano
Abstract Chiral recognition of dipeptide methyl esters by anionic heptakis[6-carboxymethylthio-6-deoxy]-,-cyclodextrin (per-CO2, -,-CD) was studied in D2O at pD 7.0 by means of 1H NMR spectroscopy. The methyl esters of alanylalanine (Ala-Ala-OMe), alanylleucine (Ala-Leu-OMe), alanyltryptophan (Ala-Trp-OMe), glycyltryptophan (Gly-Trp-OMe), valyltryptophan (Val-Trp-OMe), leucyltryptophan (Leu-Trp-OMe), and tryptophylalanine (Trp-Ala-OMe) were used as the dipeptides. The binding constant (K) determined from NMR titration increases in the order Ala-Ala-OMe < Ala-Leu-OMe < Ala-Trp-OMe, suggesting that van der Waals interactions between the host and the guest participate in complexation. Coulomb interactions between the protonated dipeptide methyl esters and the anionic host seem to be another attractive force. Per-CO2, -,-CD interacts with the (R,R)-enantiomers of the dipeptide methyl esters more strongly than the (S,S)-enantiomers. Such enantioselectivity corresponds to that for ,-amino acid methyl esters such as Leu-OMe and Trp-OMe, whose (R)-enantiomers are the preferable guests. The enantioselectivity is mainly dominated by amino acid residue at the C -terminal and chirality at the N -terminal residue plays an assistant role. An asymmetrically twisted shape of the host cavity may be essential for chiral recognition. Chirality 13:474,482, 2001. © 2001 Wiley-Liss, Inc. [source]