Pick and choose: Novel cationic diaza‐, azaoxo‐, and dioxo[6]helicenes are readily prepared and functionalized selectively by orthogonal aromatic electrophilic and vicarious nucleophilic substitutions (see scheme). Reductions, cross‐coupling, or condensation reactions introduce additional diversity and allow tuning of the absorption properties up to the near‐infrared region. The diaza salts can be
Extended Triangulenium Ions: Syntheses and Characterization of Benzo-Bridged Dioxa- and Diazatriangulenium Dyes
作者:Martin Rosenberg、Marco Santella、Sidsel A. Bogh、Alberto Viñas Muñoz、Helene O. B. Andersen、Ole Hammerich、Ilkay Bora、Kasper Lincke、Bo W. Laursen
DOI:10.1021/acs.joc.8b02978
日期:2019.3.1
The very limited class of fluorophores, with a long fluorescence lifetime (>10 ns) and fluorescence beyond 550 nm, has been expanded with two benzo-fused triangulenium derivatives and two cationic [5]-helicene salts. The syntheses of the benzo-bridged dioxa- and diazatriangulenium derivatives (BDOTA(+) and BDATA(+), respectively) required two different synthetic approaches, which reflect the structural and physiochemical impact on the reactivity of [5]-helicenium precursors. Spectroscopic investigations show that the introduction of the benzo bridge into the triangulenium chromophore significantly redshifts the absorption and emission while maintaining fluorescence lifetimes above 10 ns. The combination of a high quantum yield, long fluorescence lifetime, and emission above 600 nm is possible only if the structural aspects of the triangulenium framework are perfectly harmonized to secure a low rate of nonradiative deactivation. The new benzo bridge may be a general motif to obtain red-shifted derivatives of other dye classes.