Due to the presence of a non-aromatic cyclopentadiene ring, the spectrum is hypsochromically shifted vs. those of 1-Mes and 6-Mes. Furthermore, unlike the all-carbon [5]-and [6]helicenes C and D, which are reported to have a ΦPL of only 4%, all three azaborine helicenes studied herein exhibit stronger fluorescence with ΦPL being at least five times higher than these carbohelicenes. Among the three azaborine compounds 7-Mes shows the highest luminescence quantum yield, which may be attributed to the fluorene unit as the latter has also been reported to improve the ΦPL of carbohelicenes. The relatively small Stokes shifts (1090, 1320, and 1420 cm -1 for 1-Mes, 6-Mes, and 7-Mes, respectively) and vibrational structures of the emission spectra indicate their considerable rigidity. a Absorption and emission spectra are of 10 -5 M DCM solutions. b Calculated using 9,10diphenylanthracene as a standard. Reduction potentials were calibrated with ferrocene as an internal standard and referenced vs. Fc + /Fc.