The potential use of circularly polarized luminescence for object identification in a sensor application is demonstrated. New luminescence probes using pyrene derivatives as sensor luminophores were developed. (R,R)-Im₂ Py and (S,S)-Im₂ Py contain two chiral imidazole moieties at 1,6-positions through ethynyl spacers (angle between spacers ca. 180°). The probe molecules spontaneously self-assemble into chiral stacks (P or M helicity) upon coordination to metal ions with tetrahedral coordination (Zn²⁺ ). The chiral probes display neither circular dichroism (CD) nor circularly polarized luminescence (CPL) without metal ions. However, (R,R)-Im₂ Py and (S,S)-Im₂ Py exhibit intense chiroptical activity (CD and CPL) upon self-assembly with Zn²⁺ ions. (R,R)-Im₂ Py and (S,S)-Im₂ Py with chemical stimuli-responsibility allow sensing using the CPL signal as detection output, enabling us to discriminate between a signal from the target analyte and that from non-target species.
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Imai et al. (2018) studied this question.