Protonation-induced red-coloured circularly polarized luminescence of carbohelicene fused by benzimidazole†
Benzimidazole-fused carbohelicene (HeliBI) was newly synthesized to examine the spectroscopic and chiroptical properties. The reversible protonation and deprotonation processes of HeliBI were successfully investigated using 1H NMR, absorption and fluorescence spectral measurements. We also confirmed the circularly polarized luminescence of protonated HeliBI (H+-HeliBI). This is the first observation of red-coloured CPL of a helicene derivative.