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The synthesis and chiroptical properties of a series of enantiomerically pure, C2‐symmetrical carbo[6]helicene dimers are reported. Two helicene cores are connected through a buta‐1,3‐diyne‐1,4‐diyl linker or a heteroaromatic bridge and bear arylethynyl substituents at their 15‐positions. This ensures the possibility of extended electronic communication throughout the whole molecule. The new chromophores exhibit intense ECD spectra with strong bands in the UV/Vis region well above 400 nm. The anisotropy factor gabs (defined as Δϵ/ϵ) reaches values up to 0.047, which are unusually large for single organic molecules. They also display blue fluorescence, with good quantum yields (Φf∼0.25). The emitted light is circularly polarized to an outstanding extent: in some cases, the luminescence dissymmetry factor glum=2(IL−IR)/(IL+IR) attains values of |0.025|. To the best of our knowledge, such values are among the highest ever reported for non‐aggregated organic fluorophores. [ABSTRACT FROM AUTHOR]

We report the synthesis of enantiomerically pure carbo[6]helicene oligomers with buta-1,3-diyne-1,4-diyl bridges between the helicene nuclei. The synthesis of monomeric (±)-2,15-bis[(triisopropylsilyl)ethynyl]carbo[6]helicene was achieved in 25 % yield over six steps. Pure (+)-( P)- and (−)-( M)-enantiomers were obtained by HPLC on a chiral stationary phase. The dimeric (+)-( P)2- and (−)-( M)2-configured and the tetrameric (+)-( P)4- and (−)-( M)4-configured oligomers were obtained by sequential oxidative acetylenic coupling. The ECD spectra of the tetrameric oligomers displayed large Cotton effect intensities of Δ ϵ=−851 m−1 cm−1 at λ=370 nm (( M)4-enantiomer). We transformed the buta-1,3-diyne-1,4-diyl bridge in the dimeric ( P)2 and ( M)2 oligomer by heteroaromatization into a thiene-2,5-diyl linker. Although the resulting chromophore showed reduced ECD intensities, it exhibited a remarkably strong fluorescence emission at 450-500 nm, with an absolute quantum yield of 25 %. [ABSTRACT FROM AUTHOR]