Control of the Ketone to <i>gem</i>-Diol Equilibrium by Host−Guest Interactions

Rawashdeh, Abdel‐Monem M.; Thangavel, Arumugam; Sotiriou‐Leventis, Chariklia; Leventis, Nicholas

doi:10.1021/ol800021r

Cited by 26 publications

(23 citation statements)

References 23 publications

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“…[19] Recently, Rawashdeh et al have shown the control over the keto-diol equilibrium of Nmethyl-4-[(p-substituted)benzoyl]pyridinium cations through CB7 encapsulation. [28] In the present study, we report on the modulation of the ground-and excited-state proton-transfer processes of 2-…”

Section: Introductionmentioning

confidence: 89%

Modulation of Excited‐State Proton Transfer of 2‐(2′‐Hydroxyphenyl)benzimidazole in a Macrocyclic Cucurbit[7]uril Host Cavity: Dual Emission Behavior and pK_a Shift

Shaikh

Choudhury

Mohanty

et al. 2009

Chemistry A European J

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The effect of the macrocyclic host, cucurbit[7]uril (CB7), on the photophysical properties of the 2-(2'-hydroxyphenyl)benzimidazole (HPBI) dye have been investigated in aqueous solution by using ground-state absorption and steady-state and time-resolved fluorescence measurements. All three prototropic forms of the dye (cationic, neutral, and anionic) form inclusion complexes with CB7, with the largest binding constant found for the cationic form (K approximately 2.4x10(6) M(-1)). At pH approximately 4, the appearance of a blue emission band upon excitation of the HPBI cation in the presence of CB7 indicates that encapsulation into the CB7 cavity retards the deprotonation process of the excited cation, and hence reduces its subsequent conversion to the keto form. Excitation of the neutral form (pH approximately 8.5), however, leads to an increase in the keto form fluorescence, indicating an enhanced excited-state intramolecular proton-transfer process for the encapsulated dye. In both the ground and excited states, the two pK(a) values of the HPBI dye show upward shifts in the presence of CB7. The prototropic equilibrium of the CB7-complexed dye is represented by a six-state model, and the pH-dependent changes in the binding constants have been analyzed accordingly. It has been observed that the calculated pK(a) values using this six-state model match well with the values obtained experimentally. The changes in the pK(a) values in the presence of CB7 have been corroborated with the modulation of the proton-transfer process of the dye within the host cavity.

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Section: Introductionmentioning

confidence: 89%

Modulation of Excited‐State Proton Transfer of 2‐(2′‐Hydroxyphenyl)benzimidazole in a Macrocyclic Cucurbit[7]uril Host Cavity: Dual Emission Behavior and pK_a Shift

Shaikh

Choudhury

Mohanty

et al. 2009

Chemistry A European J

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“…Upfield shifts (Δ δ <0) are observed for guest protons located in the shielding region of the cavity, while guest protons located near the carbonyl oxygens of the portals experience deshielding and downfield shifts (Δ δ >0). Some caution must exercised in the interpretation of the shifts, as changes in the structures of the guest (complexation‐induced protonations,45 tautomerizations,46 etc.) and shifts in the electron density47 within the guests can overshadow simple shielding arguments.…”

Section: Complexation Of Guest Drug Moleculesmentioning

confidence: 99%

“…In addition to the shift in acid–base equilibria by the complexation of a weakly basic guest by cucurbit[ n ]uril host molecules, the modulation of other equilibria involving the cucurbit[ n ]uril inclusions of guest molecules have been reported. These include the control of base‐off/base‐on equilibria of vitamin B 12 molecules,31 cis ‐ trans isomerization of azobenzenes,45m lactone/carboxylate forms of camptothecin,44 keto‐ gem ‐diol equilibria of N‐methyl‐4‐( p ‐substituted benzoyl)pyridinium cations,46 and iminium/alkanolamine forms of sanguinarine 64…”

Section: Control Of Equilibria By Cucurbituril Complexationmentioning

confidence: 99%

Encapsulation of Drug Molecules by Cucurbiturils: Effects on their Chemical Properties in Aqueous Solution

Macartney

2011

Israel Journal of Chemistry

148

180

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The effects of the encapsulation of drugs and other molecules of biomedical interest by cucurbit[n]uril (n = 5-8, 10) host molecules on the chemical properties of the drugs in aqueous solution are reviewed. The cucurbituril complexation of drug molecules has been shown to generally increase the guests' pK a values through preferential inclu-sion of the protonated species, modulate other equilibria involving the guest, improve the solubility in aqueous solution, reduce the toxicity and other side effects, as well as enhance the stability and targeted delivery of the drug molecule. These benefits have led to an increasing interest in the applications of cucurbit[n]urils in novel drug formulations.

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“…2‐OOA was reversibly hydrated in an aqueous solution. In aqueous solution, some 2‐OOA existed in its keto form, with the majority existing as its gem diol . The keto form contained a UV chromophore, which could be excited in the near‐UV state to induce photolysis to form the radical intermediate 2‐OOA·.…”

Section: Resultsmentioning

confidence: 99%

Preparation of glucose‐sensitive and fluorescence micelles via a combination of photoinitiated polymerization and chemoenzymatic transesterification for the controlled release of insulin

Jiang²,

et al. 2015

J of Applied Polymer Sci

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Glucose-sensitive and fluorescence copolymer micelles were designed and prepared via a combination of photoinitiated polymerization and enzymatic transesterification. The water-soluble photoinitiator and emulsifier 2-oxooctanoic acid self-polymerized dimer molecules under UV irradiation were characterized by mass spectrometry. The fluorescence dye (9-anthracene alcohol) and biocompatible hydrophilic chains [poly(ethylene glycol)] were introduced to the polymer chains during the photopolymerization and enzymatic transesterification processes. The as-prepared copolymers were confirmed by 1 H-NMR spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, and dynamic light scattering. The resulting copolymers exhibited excellent glucose sensitivity and stability against protein. The optical fluorescence properties of the copolymer micelles were investigated with fluorescence spectrophotometry, fluorescence microscopy, and confocal laser scanning microscopy. Because of the amphiphilic feature, the micelles could be self-assembled and used to load insulin. The controlled release of insulin was evaluated and was triggered by glucose in vitro. This study provided a new strategy for fabricating functional carriers as self-regulated insulin-release systems. V C 2015Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43026.

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Control of the Ketone to gem-Diol Equilibrium by Host−Guest Interactions

Cited by 26 publications

References 23 publications

Modulation of Excited‐State Proton Transfer of 2‐(2′‐Hydroxyphenyl)benzimidazole in a Macrocyclic Cucurbit[7]uril Host Cavity: Dual Emission Behavior and pK_a Shift

Modulation of Excited‐State Proton Transfer of 2‐(2′‐Hydroxyphenyl)benzimidazole in a Macrocyclic Cucurbit[7]uril Host Cavity: Dual Emission Behavior and pK_a Shift

Encapsulation of Drug Molecules by Cucurbiturils: Effects on their Chemical Properties in Aqueous Solution

Preparation of glucose‐sensitive and fluorescence micelles via a combination of photoinitiated polymerization and chemoenzymatic transesterification for the controlled release of insulin

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Control of the Ketone to gem-Diol Equilibrium by Host−Guest Interactions

Cited by 26 publications

References 23 publications

Modulation of Excited‐State Proton Transfer of 2‐(2′‐Hydroxyphenyl)benzimidazole in a Macrocyclic Cucurbit[7]uril Host Cavity: Dual Emission Behavior and pKa Shift

Modulation of Excited‐State Proton Transfer of 2‐(2′‐Hydroxyphenyl)benzimidazole in a Macrocyclic Cucurbit[7]uril Host Cavity: Dual Emission Behavior and pKa Shift

Encapsulation of Drug Molecules by Cucurbiturils: Effects on their Chemical Properties in Aqueous Solution

Preparation of glucose‐sensitive and fluorescence micelles via a combination of photoinitiated polymerization and chemoenzymatic transesterification for the controlled release of insulin

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Product

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Modulation of Excited‐State Proton Transfer of 2‐(2′‐Hydroxyphenyl)benzimidazole in a Macrocyclic Cucurbit[7]uril Host Cavity: Dual Emission Behavior and pK_a Shift

Modulation of Excited‐State Proton Transfer of 2‐(2′‐Hydroxyphenyl)benzimidazole in a Macrocyclic Cucurbit[7]uril Host Cavity: Dual Emission Behavior and pK_a Shift