A two-dimensional confined polyoxometalate-based chiral luminescence sensor for highly enantioselective sensing†

Abstract

Chiral recognition, particularly the recognition of different enantiomers of chiral drugs, is important for human life and health safety. Here, we designed a two-dimensional (2D) confined polyoxometalate-based chiral luminescence 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 luminescence sensing for cinchonine/cinchonidine (CN/CND) with the K_SV-CN/K_SV-CND (K_SV = quenching constant) of 1.60 compared to achiral Mg₃Al–EuW₁₀ with the K_SV-CN/K_SV-CND of 1.02, and the quantitative determination of the enantiomeric excess was performed. 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 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*).