Synthesis, aggregation, and binding behavior of synthetic amphiphilic receptors

A.P.H.J. Schenning, B. Escuder, J.L.M. Nunen, van, B. Bruin, de, D.W.P.M. Lowik, A.E. Rowan, S.J. Gaast, van der, M.C. Feiters, R.J.M. Nolte

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Abstract

Amphiphilic bowl-shaped receptor molecules have been synthesized starting from diphenylglycoluril. Upon dispersion in water, these molecules self-assemble to form vesicles that bind neutral guests and alkali metal ions. In the case of bis(alkylester)-modified receptor compound 4, electron microscopy reveals that an increase in the size of the alkali metal ion (from Na+ or K+ to Rb+ and to Cs+) leads to a change in the shape of the aggregates, viz. from vesicles to tubules. Monolayer experiments suggest that this behavior is due to a change in the conformation of this amphiphilic receptor. In water, molecules of 4 have an elongated conformation that changes to a sandwich-like one upon binding of alkali metal ions. Binding studies with vesicles from the bis-ammonium receptors 6 and 9 and the guest 4-(4-nitrophenylazo)resorcinol (Magneson) reveal that below the critical aggregation concentration (CAC) of the amphiphile 1:1 host-guest complexes are formed with high host-guest association constants. Above the CAC, a host-guest ratio of 2:1 was observed that indicates that only the cavities on the outside of the vesicle can be occupied. In the case of the naphthalene walled compound 8 changes in the vesicle structure are induced by the organic guest Magneson.
Original languageEnglish
Pages (from-to)1538-1547
JournalJournal of Organic Chemistry
Volume66
Issue number5
DOIs
Publication statusPublished - 2001

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