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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]

The synthetic access to macrocyclic molecular topologies with interesting photophysical properties has greatly improved thanks to the successful implementation of organic and inorganic corner units. Based on recent reports, we realized that pseudo‐meta [2.2]paracyclophanes (PCPs) might serve as optimal corner units for constructing 3D functional materials, owing to their efficient electronic communication, angled substituents and planar chirality. Herein, we report the synthesis, characterization and optical properties of four novel all‐carbon enantiopure macrocycles bearing three to six pseudo‐meta PCPs linked by 1,3‐butadiyne units. The macrocycles were obtained by a single step from enantiopure, literature‐known dialkyne pseudo‐meta PCP and were unambiguously identified and characterized by state of the art spectroscopic methods and in part even by x‐ray crystallography. By comparing the optical properties to relevant reference compounds, it is shown that the pseudo‐meta PCP subunit effectively elongates the conjugated system throughout the macrocyclic backbone, such that already the smallest macrocycle consisting of only three subunits reaches a polymer‐like conjugation length. Additionally, it is shown that the chiral pseudo‐meta PCPs induce a remarkable chiroptical response in the respective macrocycles, reaching unprecedented high molar circular dichroism values for all‐carbon macrocycles of up to 1307 L mol−1 cm−1. [ABSTRACT FROM AUTHOR]

We report the design of a synthetically easy accessible axial chirality-inducing framework for a chromophore of choice. The scaffold consists of two basic para-phenylene-ethynylene backbones separated by laterally placed corner units. Substitution with an inherently achiral chromophore at the 2 and 5 positions of the central phenylene excitonically couples the chromophore associated transition and thereby results in chiroptical properties. Using 6-methoxynaphthalene as a model chromophore, we present the synthesis, structural analysis and spectroscopic investigation of the framework. The chiral framework was synthesized in three straightforward synthetic steps and fully characterized. The obtained racemic compounds were resolved using HPLC and assignment of the absolute configuration was performed using the exciton chirality method, crystallography and DFT calculations. This simple yet potent framework might prove useful to enrich the structural diversity of chiral materials. [ABSTRACT FROM AUTHOR]

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]

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. [ABSTRACT FROM AUTHOR]

Front Cover: Intense Molar Circular Dichroism in Fully Conjugated All-Carbon Macrocyclic 1,3-Butadiyne Linked pseudo-meta [2.2]Paracyclophanes (Chem. Eur. J. 53/2022) The angle and flexibility of the pseudo- I meta i substituents enabled high yielding macrocyclization reactions, and the studied trimeric, tetrameric, pentameric and hexameric structures further displayed astonishing through-space polymer-like conjugation lengths. Keywords: [2.2]paracyclophane; hydrocarbon; macrocycle; molar circular dichroism; -conjugation EN [2.2]paracyclophane hydrocarbon macrocycle molar circular dichroism -conjugation 1 1 1 09/27/22 20220922 NES 220922 B Unprecedented high molar circular b dichroism values for all-carbon macrocycles were revealed in 1,3-butadiyne bridged pseudo- I meta- i [2.2]paracyclophanes. [Extracted from the article]