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Chiral organic molecules possessing high quantum yields, circular dichroism, and circularly polarized luminescence values have great potential as optically active materials for future applications. Recently, the identification of a promising class of inherently chiral compounds was reported, namely macrocyclic 1,3‐butadiyne‐linked pseudo‐meta[2.2]paracyclophanes, displaying high circular dichroism and related gabs values albeit modest quantum yields. Increasing the quantum yields in an attempt to get bright circularly polarized light emitters, the high‐yielding heterocyclization of those 1,3‐butadiyne bridges resulting in macrocyclic 2,5‐thienyls‐linked pseudo‐meta [2.2]paracyclophanes is herein described. The chiroptical properties of both, the previously reported 1,3‐butadiyne, and the novel 2,5‐thienyl bridged macrocycles of various sizes, are experimentally recorded, and theoretically described using density‐functional theory. [ABSTRACT FROM AUTHOR]

Invited for the cover of this issue is the group of Marcel Mayor at the University of Basel with co-workers Olaf Fuhr and Dieter Fenske from Karlsruhe Institute of Technology. The image depicts the studied all-carbon polygon shaped macrocycles along with their intense circular dichroism spectra in the background. The bright light within the macrocycles displays its efficient conjugation. Read the full text of the article at 10.1002/chem.202201764., (© 2022 Wiley-VCH GmbH.)

The synthesis and chiroptical properties of a series of enantiomerically pure, C 2 -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 g abs (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 (Φ f ∼0.25). The emitted light is circularly polarized to an outstanding extent: in some cases, the luminescence dissymmetry factor g lum =2(I L -I R )/(I L +I R ) attains values of |0.025|. To the best of our knowledge, such values are among the highest ever reported for non-aggregated organic fluorophores., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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 Δϵ=-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 %., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)