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Article: Effect of cyclodextrin dimers with bipyridyl and biphenyl linking groups on carboxyl ester hydrolysis catalyzed by zinc complex
Title | Effect of cyclodextrin dimers with bipyridyl and biphenyl linking groups on carboxyl ester hydrolysis catalyzed by zinc complex |
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Authors | |
Keywords | Carboxylic Ester Cyclodextrin Dimer Hydrolysis Kinetics Zinc Complex |
Issue Date | 2009 |
Publisher | Elsevier BV. The Journal's web site is located at http://www.elsevier.com/locate/molcata |
Citation | Journal Of Molecular Catalysis A: Chemical, 2009, v. 308 n. 1-2, p. 61-67 How to Cite? |
Abstract | Two new β-cyclodextrin dimers, biphenyl-4,4′-bis(6-monodeoxy-6-ammoniomethyl-β-cyclodextrin) (Host 1, H1) and 2,2′-bipyridyl-5,5′-bis(6-monodeoxy-6-ammoniomethyl-β-cyclodextrin) (Host 2, H2), were synthesized and further assembled with a zinc complex containing a hydrophobic group to construct two host-guest systems, ZnL(H1) and ZnL(H2) (L = 4-(4′-tert-butylbenzyl)diethylenetriamine), acting as supramolecular metallohydrolase models. In such system, the chemical equilibrium constants were determined by pH potentiometric titration at 298 ± 0.1 K. Two deprotonation constants of the Zn(II)-coordinated water, 8.68 ± 0.03 (pKa1) and 10.50 ± 0.04 (pKa2), were obtained respectively for the ZnL(H1) system whereas only one pKa1 value was obtained for ZnL(H2) (9.38 ± 0.02). The kinetics of p-nitrophenyl acetate (pNA) hydrolysis catalyzed by ZnL(H1) and ZnL(H2) were examined respectively from pH 7.56 to 10.56 at 298 ± 0.1 K. The pH profile of rate constant of pNA hydrolysis catalyzed by ZnL(H1) exhibits an exponential increase with second-order rate constants of 0.98 and 8.41 M-1 s-1 for mono- and di-hydroxyl active species, indicating a potent catalytic activity relative to the reported mononuclear and polynuclear Zn(II) species. However, the pH profile of rate constant of hydrolysis catalyzed by ZnL(H2) only shows a saturated kinetic behavior with the second-order rate constant of 1.26 M-1 s-1, suggesting a kinetic process controlled only by an acid-base equilibrium. All kinetic results are in good agreement with thermodynamic data for hydroxyl activated species in ZnL(H1) and ZnL(H2) systems. © 2009 Elsevier B.V. All rights reserved. |
Persistent Identifier | http://hdl.handle.net/10722/168385 |
ISSN | 2018 Impact Factor: 5.008 |
ISI Accession Number ID | |
References |
DC Field | Value | Language |
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dc.contributor.author | Zhou, YH | en_US |
dc.contributor.author | Zhao, M | en_US |
dc.contributor.author | Sun, H | en_US |
dc.contributor.author | Mao, ZW | en_US |
dc.contributor.author | Ji, LN | en_US |
dc.date.accessioned | 2012-10-08T03:18:17Z | - |
dc.date.available | 2012-10-08T03:18:17Z | - |
dc.date.issued | 2009 | en_US |
dc.identifier.citation | Journal Of Molecular Catalysis A: Chemical, 2009, v. 308 n. 1-2, p. 61-67 | en_US |
dc.identifier.issn | 1381-1169 | en_US |
dc.identifier.uri | http://hdl.handle.net/10722/168385 | - |
dc.description.abstract | Two new β-cyclodextrin dimers, biphenyl-4,4′-bis(6-monodeoxy-6-ammoniomethyl-β-cyclodextrin) (Host 1, H1) and 2,2′-bipyridyl-5,5′-bis(6-monodeoxy-6-ammoniomethyl-β-cyclodextrin) (Host 2, H2), were synthesized and further assembled with a zinc complex containing a hydrophobic group to construct two host-guest systems, ZnL(H1) and ZnL(H2) (L = 4-(4′-tert-butylbenzyl)diethylenetriamine), acting as supramolecular metallohydrolase models. In such system, the chemical equilibrium constants were determined by pH potentiometric titration at 298 ± 0.1 K. Two deprotonation constants of the Zn(II)-coordinated water, 8.68 ± 0.03 (pKa1) and 10.50 ± 0.04 (pKa2), were obtained respectively for the ZnL(H1) system whereas only one pKa1 value was obtained for ZnL(H2) (9.38 ± 0.02). The kinetics of p-nitrophenyl acetate (pNA) hydrolysis catalyzed by ZnL(H1) and ZnL(H2) were examined respectively from pH 7.56 to 10.56 at 298 ± 0.1 K. The pH profile of rate constant of pNA hydrolysis catalyzed by ZnL(H1) exhibits an exponential increase with second-order rate constants of 0.98 and 8.41 M-1 s-1 for mono- and di-hydroxyl active species, indicating a potent catalytic activity relative to the reported mononuclear and polynuclear Zn(II) species. However, the pH profile of rate constant of hydrolysis catalyzed by ZnL(H2) only shows a saturated kinetic behavior with the second-order rate constant of 1.26 M-1 s-1, suggesting a kinetic process controlled only by an acid-base equilibrium. All kinetic results are in good agreement with thermodynamic data for hydroxyl activated species in ZnL(H1) and ZnL(H2) systems. © 2009 Elsevier B.V. All rights reserved. | en_US |
dc.language | eng | en_US |
dc.publisher | Elsevier BV. The Journal's web site is located at http://www.elsevier.com/locate/molcata | en_US |
dc.relation.ispartof | Journal of Molecular Catalysis A: Chemical | en_US |
dc.subject | Carboxylic Ester | en_US |
dc.subject | Cyclodextrin Dimer | en_US |
dc.subject | Hydrolysis | en_US |
dc.subject | Kinetics | en_US |
dc.subject | Zinc Complex | en_US |
dc.title | Effect of cyclodextrin dimers with bipyridyl and biphenyl linking groups on carboxyl ester hydrolysis catalyzed by zinc complex | en_US |
dc.type | Article | en_US |
dc.identifier.email | Sun, H:hsun@hkucc.hku.hk | en_US |
dc.identifier.authority | Sun, H=rp00777 | en_US |
dc.description.nature | link_to_subscribed_fulltext | en_US |
dc.identifier.doi | 10.1016/j.molcata.2009.03.026 | en_US |
dc.identifier.scopus | eid_2-s2.0-67649491444 | en_US |
dc.relation.references | http://www.scopus.com/mlt/select.url?eid=2-s2.0-67649491444&selection=ref&src=s&origin=recordpage | en_US |
dc.identifier.volume | 308 | en_US |
dc.identifier.issue | 1-2 | en_US |
dc.identifier.spage | 61 | en_US |
dc.identifier.epage | 67 | en_US |
dc.identifier.isi | WOS:000268359900008 | - |
dc.publisher.place | Netherlands | en_US |
dc.identifier.scopusauthorid | Zhou, YH=13104031900 | en_US |
dc.identifier.scopusauthorid | Zhao, M=23972068800 | en_US |
dc.identifier.scopusauthorid | Sun, H=7404827446 | en_US |
dc.identifier.scopusauthorid | Mao, ZW=23989068600 | en_US |
dc.identifier.scopusauthorid | Ji, LN=20734334600 | en_US |
dc.identifier.issnl | 1381-1169 | - |