Elucidating dissociation activation energies in host-guest assemblies featuring fast exchange dynamics

Area of Science:

• Supramolecular Chemistry
• Physical Chemistry
• Chemical Kinetics

Background:

• Controlling kinetic properties and dissociation activation energies (Ea) of guests in host-guest systems is crucial for their design and function.
• Experimental quantification of fast kinetic parameters in host-guest systems has been challenging with existing methods.

Purpose of the Study:

• To demonstrate the utility of the NMR-based guest exchange saturation transfer (GEST) approach for quantifying dissociation kinetics in host-guest systems.
• To investigate the role of "supramolecular lids" in mediating guest dissociation activation energy (Ea,out).

Main Methods:

• Utilized the guest exchange saturation transfer (GEST) technique, an NMR-based method.
• Assessed the effect of monovalent cations on dissociation activation energy (Ea,out) in cucurbit[7]uril:guest systems.
• Quantified dissociation exchange rates (k_out) and activation energies (Ea,out) in systems with fast dissociation dynamics.

Main Results:

• Successfully quantified dissociation exchange rates (k_out) and activation energies (Ea,out) using GEST in systems with fast dissociation dynamics.
• Demonstrated that "supramolecular lids" effectively mediate the guest's dissociation activation energy (Ea).
• Highlighted the influence of different monovalent cations on the extracted Ea,out values.

Conclusions:

• The GEST approach is effective for studying fast kinetic parameters in host-guest systems.
• Supramolecular lids play a significant role in modulating guest dissociation kinetics and activation energies.
• GEST can be extended to study other supramolecular systems and aid in designing novel switchable host-guest assemblies.