Ester Cleavage by Cyclodextrins in Aqueous Dimethyl Sulfoxide Mixtures. Substrate Binding versus Transition State Binding

Tee, Oswald S.; Mazza, Charles; Lozano-Hemmer, Rafael; Giorgi, Javier B.

doi:10.1021/jo00104a014

Cited by 37 publications

(18 citation statements)

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“…Given this observation, one might infer that hydrophobic interactions (27) largely determine the binding of aliphatics to CDs in aqueous solution but one must recognize that the size and surface area of alkyl chains also increase linearly with N, so that van der Waals interactions (4) may contribute to the chain length dependence, as well. Consistent with this latter view, we have found that the binding of nitrophenyl alkanoate esters to both a-CD and P-CD shows a significant, but reduced, dependence on chain length in 60% aqueous DMSO, even though hydrophobic effects are largely absent in this medium (28).…”

Section: Discussionsupporting

confidence: 80%

Dissociation constants of host–guest complexes of alkyl-bearing compounds with β-cyclodextrin and "hydroxypropyl-β-cyclodextrin"

Tee¹,

Gadosy²,

Giorgi³

1996

Can. J. Chem.

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Dissociation constants (Kd) of host-guest complexes formed from P-cyclodextrin or "hydroxypropyl-P-cyclodextrin" (P-CD and Hp-P-CD) and several types of aliphatic guests (alcohols, alkanesulfonate ions, alkylamines, and a-amino acids), with up to eight carbons in a chain, are reported. These constants were determined by inhibition kinetics and by a spectrofluorometric displacement method based on competition with 1-anilino-8-naphthalenesulfonate ion as a fluorescent probe. The value of Kd for a particular amine is close to that for the corresponding alcohol. For linear alkyl derivatives, there are strong correlations between pK, (= -log Kd) and the chain length of the guest, with slopes around 0.5, complementing trends that were noted earlier. Furthermore, the strengths of binding of various aliphatic derivatives to P-CD and to Hp-P-CD are close, with Kd values for the two CDs usually being within a factor of 2 of each other. Overall, for the binding of over 50 alkyl-bearing derivatives, there is a good correlation of pKd for Hp-P-CD with that for P-CD, with unit slope. These observations imply that the binding of simple aliphatic guests to Hp-P-CD is not greatly influenced by the modification of the hydroxyl groups on the primary side of the P-CD cavity but this may not be true for longer aliphatic derivatives (>Cx) or for aromatics that penetrate farther into the CD cavity.

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Section: Discussionsupporting

confidence: 80%

Dissociation constants of host–guest complexes of alkyl-bearing compounds with β-cyclodextrin and "hydroxypropyl-β-cyclodextrin"

Tee¹,

Gadosy²,

Giorgi³

1996

Can. J. Chem.

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“…The last point to emphasize is that complexes may be obtained in mixtures of water and organic solvents such as Dossier Luminescence spectroscopy DMF, acetonitrile, DMSO [61]. In these solutions, the percentage (v/v) of solvent may reach 60 % in the case of DMF and DMSO.…”

Section: Different Complexes May Be Obtained For a Given Analytementioning

confidence: 99%

“…However in chemical applications, the same CDs have been used with other classes of molecules to catalyze various reactions, namely hydrolytic reactions [61,80,81]. In the case of mixed solvents, these reactivity studies show that the organic molecule solvents occupy the cavity of the CD in different ways according to their nature and structure, so that a different space is available for the included analyte [81].…”

Section: Other Applicationsmentioning

confidence: 99%

Luminescence in organized media and supramolecular interactions:physicochemical aspects and applications

Lerner¹,

Martín²

2000

Analusis

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Introduction Molecular luminescence of analytes in organized media or in supramolecular complexes of cyclodextrinsThe photophysical and photochemical behaviour of molecules complexed to cyclodextrins (CD) is generally different from their behaviour in solution. The first observations in the field were qualitative and were related to the increased stabilisation of labile molecules, mostly drugs, against photodegradation when complexed to natural cyclodextrins [1]. Complexation by CD's was then the preferred subject for those involved in supramolecular chemistry and drug vectorisation techniques [2] as well as in separation techniques [3][4][5]. Stabilization of a molecule against photochemical degradation is still very important in the field of pharmaceutical sciences. A recent example is the stabilisation of promazine as an inclusion complex with β-cyclodextrin [6]. Other photochemists were attracted quite early to this field of research and initiated studies, which were mostly photophysical in nature [7,8]. The key observation was that the formation of supramolecular complexes of analytes with cyclodextrins (CDs) resulted in an increase of their fluorescence quantum yield or even in the appearance of room temperature phosphorescence (RTP) [9][10][11][12]. This enhancement has been used to increase the sensitivity and the selectivity in both luminescence and chromatographic techniques [13-15].We will not say more about RTP with CDs as the subject will be developed in another contribution in the same issue of this Journal. However RTP is also observed in the solubilization of analytes in micellar colloïdal solutions and this field will be reviewed hereunder.These properties have been used to develop analytical techniques, which combine the selectivity of complexation with an enhanced emission [16][17][18][19]. In this way an improvement in the detection limits is obtained in many separation techniques such as HPLC, capillary electrophoresis (CE) or planar chromatography. Furthermore these molecular interactions allow to reveal or to stabilize new molecular forms or to turn species which are normally non-emitting into luminescent ones. All these aspects are reviewed hereunder after a short summary on the nature of the intermolecular interactions, which lie at the heart of these effects. Nature of the interactions between an analyte and a CD or a micelleWithout going into a thorough analysis of the origin of the interactions which exist between molecules in dense media which concern us here, it seems useful to recall the most important factors which should be taken into account when any type of luminescence, fluorescence or phosphorescence is involved.

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“…[33,34] Based on the existence of solvent effects, herein twosolvent systems of deionized aqueous solution and ethanol solution were considered. There is evidence that the nature of the solvent can influence or control the structure of the complex.…”

Section: Solvent Effectsmentioning

confidence: 99%

The Determination of Non-covalent Complexes of Diclofenac Sodium and Cyclodextrins by Electrospray Ionization/Time-of-Flight Mass Spectrometry

Guo

2003

Analytical Letters

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The formation of the gas-phase non-covalent complexes of diclofenac sodium with cyclodextrins (CDs) was studied by electrospray ionization/time-of-flight mass spectrometry (ESI/TOFMS). The continuous variation method was utilized to elucidate the stoichiometry. Mass spectrums revealed the stoichiometric ratios of complexes with 1:1, 2:1, 3:1 and 1:2 (b-cyclodextrin:diclofenac sodium) in deionized water or ethanol. The influence of cavity size of CD and the pH values of solution on the mixture system were investigated in detail. Only one complex peak was observed in a-CD, which is different from band g-CD. These results demonstrated that ESI/ TOFMS is a complementary technique for study of the non-covalent complex.

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Ester Cleavage by Cyclodextrins in Aqueous Dimethyl Sulfoxide Mixtures. Substrate Binding versus Transition State Binding

Cited by 37 publications

References 1 publication

Dissociation constants of host–guest complexes of alkyl-bearing compounds with β-cyclodextrin and "hydroxypropyl-β-cyclodextrin"

Dissociation constants of host–guest complexes of alkyl-bearing compounds with β-cyclodextrin and "hydroxypropyl-β-cyclodextrin"

Luminescence in organized media and supramolecular interactions:physicochemical aspects and applications

The Determination of Non-covalent Complexes of Diclofenac Sodium and Cyclodextrins by Electrospray Ionization/Time-of-Flight Mass Spectrometry

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