Fluorophore incorporation allows nanomolar guest sensing and white-light emission in M4L6 cage complexes

We have prepared a series of M4L6 tetrahedral cages containing BODIPY and pyrene moieties and followed their guest-binding properties through electronic absorption and fluorescence spectroscopies. Our results indicate that these cages are capable of encapsulating anions, leading to colour and fluorescence changes; the use of fluorescence spectroscopy thus allowed for guest detection at nanomolar concentration. On the basis of our observations, we developed an inexpensive test-paper strip assay for easy and practical detection of anions. These cages were also found to encapsulate polycyclic aromatic hydrocarbons such as perylene. By manipulating the concentration of host and guest species, we developed a white-light-emitting ensemble. Additionally, these metal-organic cages were observed to react with amino acids, allowing the sensing of these analytes. These multi-functional cages interactions with light thus enable new applications.