Logical Design of Small HOMO-LUMO Gap: Tetrabenzo[ f , jk , mn , r ][7]helicene as a Small-Molecule Near-Infrared Emitter.

Helically twisted π-conjugated compounds are promising candidates for chiroptical dyes with strong circular dichroism and circularly polarized luminescence. Herein we report the synthesis of tetrabenzo[ f , jk , mn , r ][7]helicene as a near-infrared (NIR) emitter with thermally stable helical chirality. Tetrabenzo[7]helicene (C 44 H 24 ), which consists of only 44 carbon atoms, showed broad fluorescence in the NIR region up to 850 nm. On the basis of density functional theory calculations, the NIR emission was attributed to the large orbital interaction between two dibenzo[ a , c ]anthracene units.