Key points are not available for this paper at this time.
Helicates and helicenes represent two prominent classes of synthetic molecular helices, desirable for their potential in chiroptical applications. Incorporating boron into their backbone presents a promising strategy to enhance the optical properties; however, the development of boron-doped helical systems featuring tunable emission, high configurational stability, and strong chiroptical response has been limited by synthetic challenges. We report the chemistry of bora7helicene and its dimeric diborahelicate. While the dimeric form is thermodynamically favored in the haloborane precursor, saturation of the boron coordination sphere by exogenous carbene or carbone ligands induces monomerization, reverting the structure to the bora7helicene. By employing a variety of ligands, late-stage structural diversification was achieved, yielding the first examples of cationic boron helices, which show exceptional emission tunability across the entire visible spectrum, and chiroptical responses surpassing those of previously reported 7helicenes. Theoretical studies indicate that the double-helix geometry and the intramolecular charge transfer play a significant role in achieving high dissymmetry factors.
Kim et al. (Wed,) studied this question.