title: Counterion-Controlled Self-Sorting in an Amphiphilic Calixarene Micellar System.
abstract: 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.
authors.affiliation: Departamento de Química Física, Centro de Investigación en Química Biológica y Materiales Moleculares, Universidad de Santiago, 15782, Santiago, Spain.
authors.forename: Silvia
authors.initials: S
authors.lastname: Fernández-Abad
authors.affiliation: Laboratório Associado para a Química Verde (LAQV), REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, 2829-516, Monte de Caparica, Portugal.
authors.forename: Márcia
authors.initials: M
authors.lastname: Pessêgo
authors.affiliation: Laboratório Associado para a Química Verde (LAQV), REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, 2829-516, Monte de Caparica, Portugal. nunojbasilio@gmail.com.
authors.forename: Nuno
authors.identifier: http://orcid.org/0000-0002-0121-3695
authors.initials: N
authors.lastname: Basílio
authors.affiliation: Departamento de Química Física, Centro de Investigación en Química Biológica y Materiales Moleculares, Universidad de Santiago, 15782, Santiago, Spain. luis.garcia@usc.es.
authors.forename: Luis
authors.initials: L
authors.lastname: García-Río
mesh_terms: D047250:Calixarenes / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D007477:Ions / Q000737:chemistry*; D046911:Macromolecular Substances; D009682:Magnetic Resonance Spectroscopy; D008823:Micelles; D012996:Solutions / Q000737:chemistry*; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D007477:Ions; D046911:Macromolecular Substances; D008823:Micelles; D012996:Solutions; D013501:Surface-Active Agents; D047250:Calixarenes
keywords: calixarene; host-guest interactions; micelle; self-sorting; supramolecular chemistry