Probing Inclusion Complexation Mechanisms in Polycyclodextrin Nanofibers via ESR Spectroscopy.

Area of Science:

• Materials Science
• Supramolecular Chemistry
• Analytical Chemistry

Background:

• Polycyclodextrin nanofibers (poly-CD NF) show promise for molecular separations but their complexation mechanisms are unknown.
• Understanding host-guest interactions at the molecular level is crucial for optimizing poly-CD NF performance.

Purpose of the Study:

• To systematically investigate host-guest interactions in poly-CD NF using electron spin resonance (ESR) spectroscopy.
• To elucidate the effect of cyclodextrin cavity size on the inclusion complexation of guest molecules within poly-CD NF.

Main Methods:

• Utilized spin-labeled ESR spectroscopy with two nitroxide probes: TEMPO and DTBN.
• Quantified local hydrophobicity using the outer hyperfine splitting parameter (2Azz) and analyzed spectral line shapes for spin-spin interactions.
• Compared spectral signatures of poly-CD NF with pristine cyclodextrin powder forms.

Main Results:

• ESR spectra confirmed similar inclusion environments in both poly-CD NF and their corresponding powder forms.
• Distinct affinities and dynamic constraints for TEMPO and DTBN were observed across different cyclodextrin cavity sizes (α, β, γ).
• Poly-HP-β-CD NF exhibited the highest uptake of both nitroxide probes, correlating with its larger cavity size.

Conclusions:

• ESR spectroscopy is a powerful tool for probing nanoscale heterogeneity and inclusion dynamics in poly-CD NF.
• Cyclodextrin cavity size is a key factor influencing binding affinity and retention in poly-CD NF adsorbents.
• Findings provide fundamental insights for designing advanced filtration materials for water purification and molecular recognition.