10016-20-3Relevant articles and documents
NMR Detection of Simultaneous Formation of [2]- and [3]Pseudorotaxanes in Aqueous Solution between α-Cyclodextrin and Linear Aliphatic α,ω-Amino acids, an α,ω-Diamine and an α,ω-Diacid of Similar Length, and Comparison with the Solid-State Structures
Eliadou, Kyriaki,Yannakopoulou, Konstantina,Rontoyianni, Aliki,Mavridis, Irene M.
, p. 6217 - 6226 (1999)
The interactions of 11-aminoundecanoic acid (1), 12-aminododecanoic acid (2), 1,12-diaminododecane (3), and 1,13-tridecanoic diacid (4) with α-cyclodextrin (αCD) were studied in aqueous solution by NMR spectroscopy. The association modes were established with titration and continuous variation plots, variable temperature NMR spectra, and dipolar interactions as recorded in 2D ROESY spectra. The studies were carried out at pH 7.3 and 13.6. These long, linear bifunctional molecules were found to form simultaneously [2]- and [3]pseudorotaxanes with αCD in the aqueous solution. At the higher pH the 1:1 adducts were present at concentrations higher than at the neutral pH. The longer guests formed complexes enriched in the 2:1 constituent at both pH values. There were clear indications that the [2]pseudorotaxanes are present in two isomeric forms. The presence of isomers also in the [3]pseudorotaxanes was not ruled out. Various exchange rate regimes were observed; clearly in neutral solutions the formation of the 1:1 complexes was fast in the NMR time scale, whereas the threading of a second αCD ring was a slower process. In the solid state, the adduct of αCD/2 had the structure of a [3]pseudorotaxane, in accordance with previously solved crystal structures of αCD/3 and βCD/4. The species in solution, in contrast with those present in the solid state, are therefore of varying nature, and thus the frequently and conveniently assumed 1:1 stoichiometry in similar systems is an oversimplification of the real situation.
Solid state polycondensation within cyclodextrin channels leading to watersoluble polyamide rotaxanes
Wenz, Gerhard,Steinbrunn, Marc Boris,Landfester, Katharina
, p. 15575 - 15592 (1997)
α,ω-Aminocarboxylic acids form microcrystalline inclusion compounds with α-cyclodextrin. In these inclusion compounds cyclodextrins build up channel structures, in which the α,ω-aminocarboxylic acids can be polycondensed at 200-240°C. As the resulting pol
Thermodynamic and nuclear magnetic resonance study of the reactions of α- and β-cyclodextrin with acids, aliphatic amines, and cyclic alcohols
Rekharsky, Mikhail V.,Mayhew, Martin P.,Goldberg, Robert N.,Ross, Philip D.,Yamashoji, Yuko,Inoue, Yoshihisa
, p. 87 - 100 (1997)
Titration calorimetry was used to determine equilibrium constants and standard molar enthalpy, Gibbs energy, and entropy changes for the reactions of a series of acids, amines, and cyclic alcohols with α- and β-cyclodextrin. The results have been examined in terms of structural features in the ligands such as the number of alkyl groups, the charge number, the presence of a double bond, branching, and the presence of methyl and methoxy groups. The values of thermodynamic quantities, in particular the standard molar Gibbs energy, correlate well with the structural features in the ligands. These structural correlations can be used for the estimation of thermodynamic quantities for related reactions. Enthalpy-entropy compensation is evident when the individual classes of substances studied herein are considered, but does not hold when these various classes of ligands are considered collectively. The NMR results indicate that the mode of accommodation of the acids and amines in the α-cyclodextrin cavity is very similar, but that the 1-methyl groups in 1-methylhexylamine and in 1-methylheptylamine and the N-methyl group in N-methylhexylamine lie outside the α-cyclodextrin cavity. This latter finding is consistent with the calorimetric results. Many of the thermodynamic and NMR results can be qualitatively understood in terms of van der Waals forces and hydrophobic effects.
Kinetics of the self-assembly of α-cyclodextrin [2]pseudorotaxanes with 1,12-bis(4-(α-alkyl-α-methylmethanol)pyridinium)dodecane dications in aqueous solution
Smith, A. Catherine,Macartney, Donal H.
, p. 9243 - 9251 (1998)
The kinetics and thermodynamics of the self-assembly of a series of [2]pseudorotaxanes comprised of α-cyclodextrin (α-CD) and racemic 1,12- bis(4-(α-alkyl-α-methylmethanol)pyridinium)dodecane dications (L(CH2)12L2+) in aqueous solutions have been investigated using 1H NMR spectroscopy. The mechanism of assembly involves inclusion of the α-methyl- α-alkylmethanol substituent groups (-C(CH3)(OH)R, where R = Me, Et, Pr, Bu, allyl, and 4-butenyl) by α-CD, followed by a rate-determining passage of the cyclodextrin over the pyridinium group onto the dodecamethylene chain. Dicationic threads containing end groups with R = Ph or i-Pr or where L = 4- (α,α-diethylmethanol)-pyridinium did not form α-cyclodextrin pseudorotaxanes, even after prolonged heating. The trends in the rate and activation parameters may be related to the size, shape, and hydrophobicity of the alkyl substituents and are compared with several other systems from the literature. An increase in the length and hydrophobicity of the alkyl group increases the strength of end group inclusion and decreases the rate of threading. In addition, the presence of unsaturation in the alkyl substituent (allyl vs propyl and 4-butenyl vs butyl) results in an increase in the threading rate constant.
Volume Change on Complex Formation Between Anions and Cyclodextrins in Aqueous Solution
Hoeiland, H.,Hald, L.H.,Kvammen, O.J.
, p. 775 - 784 (1981)
Partial molal volume changes during complex formation between SCN(1-), I(1-), and ClO4(1-) and α- and β-cyclodextrin have been determined by two independent methods of measurements; one based on density measurement and subsequent calculation of apparent molal volumes, the other on differentiating the association constants with respect to pressure.Results from the two methods are in good agreement.Negative volume changes were observed for complex formation between the anions and α-cyclodextrin while zero or slightly positive values were observed for complex formation with β-cyclodextrin.The result is consistent with the idea that the anions do not become dehydrated as they form complexes with cyclodextrins.
Retardation of acetal hydrolysis by cyclodextrins and its use in probing cyclodextrin-guest binding
Tee, Oswald S.,Fedortchenko, Alexei A.,Soo, Patrick Lim
, p. 123 - 128 (1998)
Hydrolysis of benzaldehyde dimethyl acetal 1 in aqueous acid is slowed down greatly by cyclodextrins (SDs): α-CD, β-CD, hp-β-CD (hydroxypropyl-β-cyclodextrin) and γ-CD. The variations of the observed first-order rate constants (Kobs) with [CD] exhibit saturation behaviour consistent with 1:1 binding between 1 and the CDs. In the case of β-CD and hp-β-CD, the binding is relatively strong and the CD-bound acetal is unreactive. In contrast, binding of the acetal by α-CD and γ-CD is much weaker, but only with α-CD does the CD-bound form show significant reactivity. The four CD-mediated reaction, have been evaluated as probe reactions for determining dissociation constants of {CD-'guest'} complexes. In this approach, added guests attenuate the retarding effect of CD-substrate binding and cause an increase in the rate of acetal hydrolysis. The method works well for alipharic alcohols and ketones binding to β-CD and hp-β-CD, but it is less successful with α-CD because of the shallow dependence of kobs on [α-CD] in the probe action. With γ-CD, the approach is not applicable at all, because added guests cause a further reduction in the rate of acetal hydrolysis, not an increase. Various implications of these findings are discussed.
Catalysis of ester aminolysis by cyclodextrins. The reaction of alkylamines with p-nitrophenyl alkanoates
Gadosy,Boyd,Tee
, p. 6879 - 6889 (2000)
The effects of four cyclodextrins (α-CD, β-CD, hydroxypropyl-β-CD, and γ-CD) on the aminolysis of p-nitrophenyl alkanoates (acetate to heptanoate) by primary amines (n-propyl to n-octyl, isobutyl, isopentyl, cyclopentyl, cyclohexyl, benzyl) in aqueous solution have been investigated. Rate constants for amine attack on the free and CD-bound esters (k(N) and k(cN)) have ratios (k(cN)/k(N)) varying from 0.08 (retardation) to 180 (catalysis). For the kinetically equivalent process of free ester reacting with CD-bound amine (k(Nc)), the ratios k(Nc)/k(N) vary from 0.2 to 28. Either way, there is evidence of catalysis in some cases and retardation in others. Changes in reactivity parameters with structure indicate more than one mode of transition state binding to the CDs. Short esters react with short alkylamines by attack of free amine on the ester bound by its aryl group, but for longer amines, free ester reacts with CD-bound amine. Reaction of long esters with long amines, which is catalyzed by β-CD and γ-CD, involves inclusion of the alkylamino group and possibly the ester acyl group. The larger cavity of γ-CD may allow the inclusion of the ester aryl group, as well as the alkylamino group, in the transition state. Reaction between an ester bound to the CD by its acyl group and free amine appears not to be important.
Altered product specificity of a cyclodextrin glycosyltransferase by molecular imprinting with cyclomaltododecaose
Kaulpiboon, Jarunee,Pongsawasdi, Piamsook,Zimmermann, Wolfgang
, p. 480 - 485 (2010)
Cyclodextrin glycosyltransferases (CGTases), members of glycoside hydrolase family 13, catalyze the conversion of amylose to cyclodextrins (CDs), circular α-(1,4)-linked glucopyranose oligosaccharides of different ring sizes. The CD containing 12 α-D-gluc
Induced circular dichroism and UV-VIS absorption spectroscopy of cyclodextrin inclusion complexes: Structural elucidation of supramolecular azi-adamantane
Krois, Daniel,Brinker, Udo H.
, p. 11627 - 11632 (1998)
The first induced circular dichroism (ICD) analyses of diazirineγyciodextrin inclusion complexes are reported. The stoichiometries and association constants of the guestηost complexes with α-, β-, and γ- cyclodextrin were determined. In addition, with the α-cyclodextrin complex, UV-vis spectroscopy of water-ethanol solutions showed remarkable fine structure, probably indicating that the diazirine experiences a nonpolar microenvironment. These analytical methods provide details about the architecture and nature of these supramolecular carbene precursors.
Cyclodextrin Inclusion Complexes of 1-Pyrenebutyrate: The Role of Coinclusion of Amphiphiles
Herkstroeter, William G.,Martic, Peter A.,Evans, Ted R.,Farid, Samir
, p. 3275 - 3280 (1986)
Several inclusion complexes with various stoichiometries are formed from 1-pyrenebutyrate ion (P) and the different cyclodextrins (α-, β-, and γ-CD).With α- and β-CD, the initially formed 1:1 complexes lead to the formation of 1:2 complexes (P*α2 and P*β2).As P can be only partially included in the small cavity of α-CD, the equilibrium constants for the formation of both complexes of α-CD are about an order of magnitude smaller than those of β-CD.For the same reason, P*β2, to which we assign a "barrel" configuration, is also an order of magnitude more effective than P*α2 in protecting singlet-excited P against quenching by triethanolamine.We had shown earlier that with γ-CD the 1:1 complex (P*γ) dimerizes to a 2:2 complex (P2*γ2), to which we also assigned a barrel configuration.The lack of efficient 1:2 complex formation in this case is attributed to the large size of the "barrel" enclosed by two γ-CD molecules.The extra space next to a single P molecule in such a cavity would have to be filled with water.However, the formation of a 1:2 inclusion complex between P and γ-CD can be induced by the coinclusion of a molecule with a hydrophobic moiety such as sodium hexanesulfonate (X).This replaces the water within the cavity and leads to the formation of P*X*γ2.This complex provides the highest degree of protection against quenching of excited P in these inclusion complexes.
