Partially Sulfated Pillar[5]Arenes: Synthesis and Molecular Recognition Properties

Area of Science:

• Supramolecular Chemistry
• Materials Science

Background:

• Pillar[5]arenes are macrocyclic hosts with tunable properties.
• Sulfation of macrocycles can enhance water solubility and alter binding characteristics.

Purpose of the Study:

• To synthesize and characterize a series of sulfated pillar[5]arene hosts (P5Sn) with varying degrees of sulfation.
• To investigate the impact of sulfate substituents on host solubility, self-association, and guest binding thermodynamics.
• To explore the potential applications of these tailored hosts in supramolecular chemistry.

Main Methods:

• Synthesis and characterization of sulfated pillar[5]arenes.
• Solubility measurements and 1H NMR dilution experiments to assess self-association.
• X-ray crystallography to determine host-guest complex structures.
• Isothermal titration calorimetry (ITC) to quantify binding thermodynamics.

Main Results:

• Five sulfated pillar[5]arene hosts (P5S2-P5S10) were successfully synthesized, exhibiting high water solubility (73-131 mM).
• NMR studies indicated minimal self-association, confirmed by crystal structures showing Me6HDA guests and intermolecular interactions.
• ITC revealed that increased sulfation enhances binding affinity (more negative free energy) for guests.
• Binding affinity also increased with the number of NMe groups on the guest molecule.

Conclusions:

• The number of sulfate substituents on pillar[5]arenes can be precisely tuned to control water solubility and host-guest binding affinity.
• These sulfated pillar[5]arenes demonstrate significant potential for applications in supramolecular polymers, separation technologies, and latching systems.
• The ability to modulate binding interactions offers a versatile platform for designing advanced functional materials.