Induced‐Fit Recognition by a Calixarene–Pyrene Conjugate for Single‐ and Dual‐Wavelength Fluorescence Sensing in Water

The discovery of fluorescence receptors that selectively bind small molecules with high affinity in aqueous media is critical for the development of new sensing and bioimaging assays. We herein report a new fluorescence receptor-dye chemosensor based on the monofunctionalization of p-sulfonatocalix[4]arene (SC4) receptor with pyrene (SC4-4Py). The SC4-4Py conjugate was found to retain the exceptional binding properties of SC4, allowing the high-affinity recognition of neurotransmitters, amino acids, and biogenic amines in aqueous solution and their optical detection. The SC4-4Py chemosensor operates through a photoinduced electron transfer (PET) mechanism triggered by conformational changes in the calixarene structure upon binding, allowing single-wavelength fluorescence detection of target analytes and its expansion into a dual-wavelength ratiometric indicator displacement assay (IDA) that relies on competitive PET between the pyrene and non-covalently bound lucigenin dye.