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

Cyclic oligomers containing porphyrinic chromophores have attracted significant attention in broad areas of science as artificial models for photosynthetic light‐harvesting antennae due to their structural and functional resemblance to natural chlorophyll arrays. Here, the synthesis of a macrocyclic [3]cycloBODIPY derivative, which consists of only boron‐dipyrromethene (BODIPY) units, via an Au‐mediated macrocyclization protocol is reported. While this [3]cycloBODIPY derivative exhibits a high total strain energy of 86.4 kcal mol −1 , part of the intrinsic strain is effectively dispersed due to the flexible boron centers. Furthermore, this [3]cycloBODIPY derivative exhibits near‐infrared (NIR) absorption reaching 1050 nm as the result of two electronic modulation factors, i.e., deformation of the BODIPY subunits and effective π‐conjugation over the entire macrocycle.