Calix[n]BODIPYs: One-Pot Assembly of Strain-Relieved Methylene-Bridged Macrocycles with Bright Fluorescence

We report a mild, one-pot synthetic approach to a family of β,β′-methylene-bridged all-BODIPY macrocycles (Calix[n]BODIPYs). Key to our design is a β-hydroxymethyl-functionalized BODIPY precursor: upon activation by BF3·OEt2, the in situ generated benzylic carbocation undergoes sequential Friedel–Crafts-type alkylation at the β-positions of adjacent BODIPY units. These macrocycles exhibit strong intramolecular excitonic coupling, exceptionally high molar extinction coefficients (up to 7.39 × 105 M–1·cm–1), and bright fluorescence (ΦFL up to 0.92).