Molecular Recognition by Pillar[5]arenes: Evidence for Simultaneous Electrostatic and Hydrophobic Interactions
Borja Gómez-González1, Luis García-Río1, Nuno Basílio2
1Departamento de Química Física, Facultade de Química, Universidade de Santiago de Compostela, 15782 Santiago, Spain.
Pharmaceutics
|January 21, 2022
Summary
This study investigated host-guest complex formation between alkylsulfonate guests and a cationic pillar[5]arene receptor in water. High binding constants were observed, driven by electrostatic and hydrophobic interactions.
Area of Science:
- Supramolecular Chemistry
- Host-Guest Chemistry
- Materials Science
Background:
- Cationic pillar[5]arenes are macrocyclic receptors with potential applications in molecular recognition.
- Understanding host-guest interactions is crucial for designing novel functional materials.
Purpose of the Study:
- To investigate the formation of inclusion complexes between alkylsulfonate guests and a cationic pillar[5]arene receptor in aqueous media.
- To elucidate the binding mechanisms and quantify the binding strength.
Main Methods:
- Nuclear Magnetic Resonance (NMR) spectroscopy to study complex structure and dynamics.
- Isothermal Titration Calorimetry (ITC) to determine thermodynamic binding parameters.
Main Results:
- Formation of stable host-guest complexes was confirmed.
- Binding is driven by a combination of electrostatic interactions and hydrophobic effects.
- Binding constants reached up to 10^7 M^-1 for guests with significant hydrophobic character.
- Structural analysis revealed inclusion of the alkyl chain within the receptor's cavity and ionic interactions of the sulfonate group at the receptor's portal.
Conclusions:
- Cationic pillar[5]arenes effectively bind alkylsulfonate guests in water.
- The binding is highly specific, influenced by guest hydrophobicity and the receptor's charged portal.
- These findings contribute to the rational design of supramolecular systems for molecular recognition and separation.
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