Remote control of anion binding by CH-based receptors

Area of Science:

• Supramolecular Chemistry
• Organic Chemistry
• Host-Guest Chemistry

Background:

• Tetra(benzimidazole)resorcin[4]arenes are macrocyclic hosts capable of molecular recognition.
• Modifying the upper rim of these hosts can influence binding properties at the opposite edge.
• Understanding structure-activity relationships is crucial for designing selective molecular sensors.

Purpose of the Study:

• To investigate the effect of electron withdrawing groups on the anion binding affinity of tetra(benzimidazole)resorcin[4]arenes.
• To explore the possibility of achieving selective anion binding at different sites within the macrocycle.
• To enhance the sensitivity and selectivity of anion recognition systems.

Main Methods:

• Synthesis of modified tetra(benzimidazole)resorcin[4]arenes bearing electron withdrawing groups.
• Anion binding studies using techniques such as Nuclear Magnetic Resonance (NMR) spectroscopy and Isothermal Titration Calorimetry (ITC).
• Computational modeling to understand the binding interactions and selectivity.

Main Results:

• Substitution with electron withdrawing groups on the upper rim increased anion binding affinity by over three orders of magnitude.
• Demonstrated selective anion binding at either the hydroxyl/amine (OH/NH) or the C-H binding sites.
• The electronic perturbations effectively modulated the host's cavity and enhanced guest interactions.

Conclusions:

• Electron withdrawing groups are effective in amplifying anion binding in tetra(benzimidazole)resorcin[4]arene systems.
• Achieved site-selective anion recognition, paving the way for sophisticated sensor development.
• This work provides a foundation for the rational design of tailored macrocyclic hosts for specific anion targets.