Iodization-enhanced fluorescence and circularly polarized luminescence for dual-readout probe design

Circularly polarized luminescence (CPL) is a preferential emission from chiral systems. Introducing CPL to traditional small fluorescence probes will greatly enhance selectivity and sensitivity due to avoiding the background fluorescence. Small-molecule probes are practically useful for bioimaging and sensing but always suffer from weak CPL properties. To optimize chiral perturbation, the study of structure-CPL correlation is an urgent necessity. Here, we investigated the influence of 3, 3′-substituent of BINOL on optical properties and found that iodization could significantly enhance the fluorescence quantum yield (ΦF) and dissymmetry factor (|glum|). Based on this finding, we presented a strategy to design dual-readout probes emiting both robust total fluorescence and CPL upon activation. As an application example, we first designed a pair of thiols probes, R/S-P1, with the fluorescence readout showing good linear response to cysteine, and CPL signal displaying significant enhancement with |glum| from undetectable value to 0.7 × 10−3.