Fluorescence detected circular dichroism (FDCD) for supramolecular host-guest complexes.

Amrutha Prabodh,Stefan Bräse,Eduard Spuling,Wei Jiang,Liu-Pan Yang,Christian Spies,Yichuan Wang,Frank Biedermann,Paolo Albertini,Stephan Sinn

doi:10.1039/d1sc01411k

Abstract

Fluorescence-detected circular dichroism (FDCD) spectroscopy is applied for the first time to supramolecular host–guest and host–protein systems and compared to the more known electronic circular dichroism (ECD). We find that FDCD can be an excellent choice for common supramolecular applications, e.g. for the detection and chirality sensing of chiral organic analytes, as well as for reaction monitoring. Our comprehensive investigations demonstrate that FDCD can be conducted in favorable circumstances at much lower concentrations than ECD measurements, even in chromophoric and auto-emissive biofluids such as blood serum, overcoming the sensitivity limitation of absorbance-based chiroptical spectroscopy. Besides, the combined use of FDCD and ECD can provide additional valuable information about the system, e.g. the chemical identity of an analyte or hidden aggregation phenomena. We believe that simultaneous FDCD- and ECD-based chiroptical characterization of emissive supramolecular systems will be of general benefit for characterizing fluorescent, chiral supramolecular systems due to the higher information content obtained by their combined use.

Highlights

Investigations into the chirality ofchemical systems and monitoring of chiral transformations have provided useful lessons for the design of drugs and functional materials and enriched the general understanding of molecular recognition principles.[1,2,3] Electronic circular dichroism (ECD) spectroscopy, which measures the difference in the absorption of le and right circularly polarized light (Fig. 1), has been extensively used for the characterization of chiral, light-absorbing molecules.[4,5,6,7]Most of thechemical compounds of interest lack a strong chromophoric group and do not produce electronic circular dichroism (ECD) signals in the practically preferable near UV or visible wavelength region, or are even completely ECD silent
We believe that simultaneous Fluorescence-detected circular dichroism (FDCD)- and ECD-based chiroptical characterization of emissive supramolecular systems will be of general benefit for characterizing fluorescent, chiral supramolecular systems due to the higher information content obtained by their combined use
We propose that molecular tube (MT) and the MT$PPO complexes form supramolecular aggregates at higher micromolar concentrations that lead to an enhanced ECD signal and sizeable uorescence-detected linear dichroism contributions to the FDCD band

Summary

Introduction

Most of the (bio)chemical compounds of interest lack a strong chromophoric group and do not produce ECD signals in the practically preferable near UV or visible wavelength region, or are even completely ECD silent. This has prompted the development of chromophoric probes and chemosensors which engage in covalent or non-covalent interactions with the chiral analyte.[8,9,10,11] The complexation of a chiral analyte by an achiral chromophoric “binder” can generally be expected to give rise to chiroptical signals because the chromophore is situated in a chiral environment.[12,13,14] Practically, suitably strong emerging

Results

Discussion

Conclusion