Rhodium-mediated enantioselective synthesis of a benzopicene-based phospha[9]helicene: the structure–property relationship of triphenylene- and benzopicene-based carbo- and phosphahelicenes

Abstract

The enantioselective synthesis of a phospha[9]helicene with a bibenzopicene skeleton has been achieved via the rhodium-mediated intermolecular [2+2+2] cycloaddition of a binaphthyl-linked tetrayne with a phosphorus-linked diyne. The photophysical and chiroptical properties of the thus obtained phospha[9]helicene were compared with our previously synthesized benzopicene-based carbo[9]helicene and triphenylene-based carbo- and phospha[7]helicenes. Significantly red shifted absorption and emission maxima were observed in the benzopicene-based phospha[9]helicene as a result of extended π-conjugation, but its fluorescence quantum yield and circularly polarized luminescence activity (g_lum) were lower than those of the other three helicenes.