Chiroptical Switching and Quantitative Chirality Sensing with (Pseudo)halogenated Quinones

Area of Science:

• Organic Chemistry
• Supramolecular Chemistry
• Analytical Chemistry

Background:

• Chiral molecules are crucial in various scientific fields, including pharmaceuticals and materials science.
• Developing efficient methods for enantiomeric analysis and creating responsive molecular systems remains a significant challenge.
• Quinones and their derivatives are versatile building blocks in organic synthesis and redox-active materials.

Purpose of the Study:

• To synthesize novel push-pull conjugates from (pseudo)halogenated quinones and chiral amines, amino alcohols, or amino acids.
• To develop a chiroptical redox switch system for optical sensing and switching applications.
• To establish a new sensing strategy for the quantitative analysis of enantiomers, even in complex mixtures.

Main Methods:

• Reaction of (pseudo)halogenated quinones with chiral amines, amino alcohols, and amino acids.
• Characterization of the resulting chiroptically active push-pull conjugates.
• Investigation of the redox switching behavior using UV-Vis and Circular Dichroism (CD) spectroscopy.
• Utilizing sodium borohydride for reduction and air exposure for re-oxidation to study the quinone/hydroquinone interconversion.
• Application of the integrated chiroptical amplification and redox switching for enantiomeric excess (ee) analysis.

Main Results:

• Smooth synthesis of push-pull conjugates with distinct optical properties.
• Demonstration of reversible redox switching between quinone and hydroquinone states with different UV and CD signatures.
• The chiroptical quinone/hydroquinone system exhibits a simple setup, uses inexpensive reagents, has a fast response time, and is thermally and photochemically stable.
• A novel sensing approach enabled on-the-fly deconvolution of overlapping CD spectra.
• Successful quantitative enantiomeric excess (ee) analysis of challenging samples containing constitutional isomers with varying enantiomeric compositions.

Conclusions:

• The developed chiroptical quinone/hydroquinone redox switch system is a versatile and robust platform for optical sensing.
• This system offers a cost-effective, stable, and rapid method for detecting and quantifying enantiomers.
• The integrated chiroptical amplification and redox switching strategy represents a significant advancement in analytical methodologies for complex chiral mixtures.