Modification of [5]Helicene with Dimesitylboryl: One Way To Enhance the Fluorescence Efficiency

The efficient synthetic route was disclosed to prepare structurally asymmetric [5]helicenes, which are substituted with either BMes(2) (7B-HC) or both BMes(2) and NMe2 (8B(5)NMe(2)-HC, 7B(5)NMe(2)-HC). Compared with the parent [5]helicene, these compounds show greatly enhanced fluorescence. In addition, they still retain fairly strong fluorescence in the solid state. Moreover, the complexation of 8B(5)NMe(2)-HC and 7B(5)NMe(2)-HC with fluoride can induce significant blue shift in fluorescence and the formed complexes are also highly fluorescent.