Synthesis, Aggregation, and Binding Behavior of Synthetic Amphiphilic Receptors

• Published in: Journal of organic chemistry Vol. 66; no. 5; pp. 1538 - 1547
• Main Authors: Schenning, Albertus P. H. J., Escuder, Beatriu, van Nunen, Johanna L. M., de Bruin, Bas, Löwik, Dennis W. P. M., Rowan, Alan E., van der Gaast, Sjerry J., Feiters, Martinus C., Nolte, Roeland J. M.
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 09-03-2001
• Subjects: Chloroform - chemistry; Electric Conductivity; Hydrogen-Ion Concentration; Metals - chemistry; Microscopy, Electron; Particle Size; Protein Binding; Protein Conformation; Receptors, Cell Surface - chemistry; Receptors, Cell Surface - metabolism; Surface-Active Agents - metabolism; Water - chemistry; X-Ray Diffraction
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo000770t

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.