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Counterion‐Controlled Self‐Sorting in an Amphiphilic Calixarene Micellar System
Author(s) -
FernándezAbad Silvia,
Pessêgo Márcia,
Basílio Nuno,
GarcíaRío Luis
Publication year - 2016
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201504649
Subject(s) - calixarene , micelle , amphiphile , counterion , chemistry , critical micelle concentration , molecular recognition , fluorescence , molecule , organic chemistry , ion , aqueous solution , copolymer , polymer , physics , quantum mechanics
Molecular recognition of small molecules and ions by artificial receptors in microheterogeneous media such as micelles and vesicles can, in principle, provide better models of biological systems in comparison with bulk solutions. In this work we have investigated the complexation of an organic fluorescent probe with amphiphilic calixarene receptor below and above the critical micelle concentration (CMC). For concentrations below the CMC, the probe forms a host–guest complex with the calixarene behaving like a traditional host–guest system operating in bulk solution. Above the CMC, multiple equilibrium processes are established and the probe can exchange between the recognition site of the calixarene in the monomeric state, micellized state and/or the micellar hydrophobic core. Careful analysis of the results obtained from NMR spectroscopy and fluorescence experiments allowed us to propose a quantitative model to describe the system. The increment of the local concentration of Na + counterions at the Stern layer displace the dye to the micelle core through competitive binding of Na + in the cavity of the receptor and is decisive for the observed self‐sorting behavior.