A cucurbit[6]uril analogue: host properties monitored by fluorescence spectroscopy

Area of Science:

• Supramolecular Chemistry
• Host-Guest Chemistry
• Fluorescence Spectroscopy

Background:

• Cucurbiturils are macrocyclic hosts with well-defined cavities.
• Developing new macrocyclic hosts with tunable properties is crucial for advanced applications.
• Intrinsic fluorescence of hosts can be leveraged for sensing and studying host-guest interactions.

Purpose of the Study:

• To characterize a novel cucurbituril analogue with an elongated cavity.
• To investigate the host-guest binding properties of this new analogue using fluorescence and NMR.
• To evaluate the potential of this new host for sensing and complexation studies.

Main Methods:

• Fluorescence spectroscopy to monitor host fluorescence changes upon guest binding.
• 1H NMR spectroscopy to confirm host-guest complexation and determine binding constants.
• Synthesis and characterization of a novel cucurbituril analogue.

Main Results:

• The new cucurbituril analogue is intrinsically fluorescent, with fluorescence sensitive to guest encapsulation.
• High binding constants were determined for benzene (K = 6900 M⁻¹) and Nile Red (K = 8.2 x 10⁶ M⁻¹).
• Binding affinities were significantly stronger than with parent cucurbituril and cyclodextrins, attributed to pi-pi interactions.

Conclusions:

• The novel cucurbituril analogue exhibits versatile host-guest complexation capabilities.
• Its fluorescence sensitivity and strong binding constants highlight its potential as a sensor and advanced host material.
• The partial aromaticity of the host walls contributes to enhanced host-guest interactions.