Multisignal Proportional Optical Chiral Sensing: Photoresponsive Molecular Probe with High Enantioselectivity for Stereospecific Molecular Recognition

The differences in the spatial structures of chiral enantiomers often lead to variations in physiological activity. Focusing on the stereoselective behavior of chiral enantiomers, timely and accurate risk assessment has become an important issue in pharmaceutical research development. The development of high-selectivity and rapid discrimination detection methods is the key to chiral enantiomer-related research. This work reports the design and synthesis of an organic small molecule light responsive probe (HBT-CN) with a chiral recognition function. HBT-CN was prepared by introducing a single configuration of cyclohexanediamine into the parent structure through a simple amide reaction using benzothiazole derivatives as fluorescent precursors. The probe has proportional enantioselective fluorescence and UV-vis absorption response to amino acid methyl ester hydrochloride enantiomers and is sensitive by using direct titration. The enantiomeric fluorescence and UV-vis absorption difference ratios of <i>R</i>/<i>S</i>-PGME were 4.5, 12.8, and 10.5, respectively. The mechanism for the enantiomeric recognition was systematically studied through fluorescence spectroscopy, fluorescence lifetime, and density functional theory calculation. Presumably, the different hydrogen bonding capacities and side chain interactions of the chiral recognition module with two enantiomers mainly contributed to the difference in the signals. Therefore, cyclohexanediamine-modified benzothiazole shows potential as a photoresponsive chiral sensing platform for enantiomeric detection.