Two-dimensional Confined Polyoxometalate-based Chiral Luminescent Sensor for High Enantioselective Sensing

Abstract

Chiral recognition, particularly the recognition for different enantiomers of chiral drugs, was an important guarantee for human life and health safety. Here, we designed a two-dimensional (2D) confined polyoxometalate-based chiral luminescent sensor by encapsulating luminescent [EuW10O36]9− clusters (EuW10) within the chiral 2D interlayer of layered double hydroxides modified with chiral ionic liquids (L-CIL−Mg3Al−EuW10). The L-CIL−Mg3Al−EuW10 sensor exhibited remarkable enantioselectivity in luminescent sensing for Cinchonine/Cinchonidine (CN/CND) with the KSV-CN/KSV-CND (KSV = quenching constant) of 1.60 compared to achiral Mg3Al−EuW10 with the KSV-CN/KSV-CND of 1.02, and the quantitative determination of the enantiomeric excess was obtained. The remarkable enantiomeric recognition ability of L-CIL−Mg3Al−EuW10 was attributed to the chiral confinement effect, which facilitated chiral induction from the L-CIL to the W–O sites in EuW10. To elucidate the diffusion dynamics within the sensor, a laser scanning confocal microscope was employed to investigate the time-resolved fluorescence quenching, revealing that CN diffused more rapidly than CND due to differences in hydrogen-bonding interactions with the L-CIL. Furthermore, Density functional theory calculations suggested that the hydrogen-bonding network formed by the analytes, L-CIL, and EuW10 enhanced the recognition ability between CN and CND enantiomers, resulting in a lower adsorption energy of adsorbed CN* (−3.38 eV for adsorbed CN* vs. −2.16 eV for adsorbed CND*).