[3]CycloBODIPY: A Highly Strained Cyclic BODIPY Trimer with Effective Macrocyclic Conjugation

Cyclic oligomers containing porphyrinic chromophores have attracted significant attention in the broad areas of science due to their structural and functional resemblance to natural chlorophyll arrays as photosynthetic light-harvesting antennae. Here, we successfully synthesized a macrocyclic system consisting of only boron-dipyrromethene (BODIPY) units, [3]cycloBODIPY, using Au-mediated macrocycle formation. While [3]cycloBODIPY exhibits a high total strain energy of 86.4 kcal mol–1, the partial strains have been effectively dispersed due to the flexible boron centers. Furthermore, [3]cycloBODIPY exhibits near-infrared (NIR) absorption up to 1050 nm because of the dual electronic modulation: the deformation of the BODIPY subunits and the effective π-conjugation over the entire macrocycle.