Modelling the Encapsulation of 3-Hydroxyflavone with Cyclodextrin and Octa Acid and Comparing Their Differences

Area of Science:

• Supramolecular Chemistry
• Fluorescence Spectroscopy
• Computational Chemistry

Background:

• 3-hydroxyflavone (3-HF) is a common fluorescence probe with dual emission bands (normal and tautomer forms).
• 3-HF exhibits poor fluorescence performance in aqueous solutions due to hydrogen bonding perturbations.
• Supramolecular chemistry offers a strategy to enhance the fluorescence properties of 3-HF in water.

Purpose of the Study:

• To review the supramolecular chemistry of 3-hydroxyflavone (3-HF) with cyclodextrins and octa acid.
• To understand how these supramolecular hosts influence the fluorescence behavior of 3-HF in water.
• To elucidate the self-assembly mechanisms and their impact on the 3-HF emission.

Main Methods:

• Review of existing literature on 3-hydroxyflavone (3-HF) interactions with cyclodextrins (β- and γ-CD) and octa acid.
• Analysis of fluorescence intensity changes and emission band shifts in aqueous solutions.
• ONIOM calculations to investigate the self-assembly of cyclodextrins and their interaction with 3-HF.

Main Results:

• β-cyclodextrin slightly enhances the tautomer form fluorescence intensity of 3-HF in water.
• γ-cyclodextrin significantly enhances the green fluorescence intensity of 3-HF in water.
• Octa acid creates a hydrophobic environment, promoting exclusive formation of the 3-HF tautomer form.
• ONIOM calculations reveal self-assembly pathways for β- and γ-cyclodextrin, explaining altered tautomer/normal form ratios.

Conclusions:

• Supramolecular complexation with cyclodextrins and octa acid effectively improves 3-hydroxyflavone (3-HF) fluorescence in aqueous media.
• The choice of supramolecular host dictates the extent of fluorescence enhancement and the relative populations of 3-HF's normal and tautomer forms.
• Computational modeling provides insights into the host-guest interactions governing the observed fluorescence modifications.