Helical β‐isoindigo‐Based Chromophores with B−O−B Bridge: Facile Synthesis and Tunable Near‐Infrared Circularly Polarized Luminescence

Abstract

AbstractIt is essential to create organic compounds that exhibit circularly polarized luminescence (CPL) in the near‐infrared (NIR) range. Helicene‐type emitters possess appealing chiroptical features, however, such NIR molecules are scarce due to a paucity of synthetic strategies. Herein, we developed a series of helical β‐isoindigo‐based B−O−B bridged aza‐BODIPY analogs that were synthesized conveniently. The reaction of diimino‐β‐isoindigo with a heteroaromatic amine produced a restricted ligand cavity, which triggered off the generation of a B−O−B bridge. The B−O−B bridge led to distorted conformations that satisfy the helical requirements, resulting in excellent spectroscopic and chiroptical properties. Tunable CPL with the highest luminescence dissymmetry factor (glum) of 1.3×10−3 and a CPL brightness (BCPL=11.5 M−1 cm−1) in the NIR region was achieved. This synthetic approach is expected to offer a new opportunity to chiral chemistry and increase flexibility for chiroptical tuning.