Publication

Assembled molecular face-rotating polyhedra to transfer chirality from two to three dimensions

6 Jul 2016 Nature Communications
XinChang Wang, Yu Wang, Huayan Yang, Hongxun Fang, Ruixue Chen, Yibin Sun, Nanfeng Zheng, Kai Tan, Xin Lu, Zhongqun Tian* and Xiao-Yu Cao*

In nature, protein subunits on the capsids of many icosahedral viruses form rotational patterns, and mathematicians also incorporate asymmetric patterns into faces of polyhedra. Chemists have constructed molecular polyhedra with vacant or highly symmetric faces, but very little is known about constructing polyhedra with asymmetric faces. Here we report a strategy to embellish a C3h truxene unit with rotational patterns into the faces of an octahedron, forming chiral octahedra that exhibit the largest molar ellipticity ever reported, to the best of our knowledge. The directionalities of the facial rotations can be controlled by vertices to achieve identical rotational directionality on each face, resembling the homo-directionality of virus capsids. Investigations of the kinetics and mechanism reveal thatnon-covalent interaction among the faces is essential to the facial homo-directionality.

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Synthesis, Structure, and Chiroptical Properties of a Double[7]Heterohelicene

18 Aug 2016 Journal of American Chemistry Society
Xiao-Ye Wang, Xin-Chang Wang, Akimitsu Narita,* Manfred Wagner, Xiao-Yu Cao,* Xinliang Feng, and Klaus Müllen*

The synthesis of 11a,25a-dibora-11,12,25,-26-tetraoxatetranaphtho[1,2-a:2′,1′-f:1″,2″-j:2‴,1‴-o]-perylene, a double [7]heterohelicene containing OBO units, has been achieved via tandem demethylationborylation, representing the highest double helicene reported thus far with all six-membered rings. Singlecrystal X-ray analysis clearly demonstrated a significantly twisted structure with the terminal aromatic rings overlapping at both ends, giving the first example of a double helicene with intramolecular π-layers. Such structural features resulted in a high theoretical isomerization barrier of 45.1 kcal/mol, which is the highest value for all the double helicenes ever reported, rendering the achieved molecule with high chiral stability. The (P,P)-and (M,M)-isomers were separated by chiral HPLC and the chiroptical properties were investigated, revealing opposite circular dichroism responses.

[full-text] [SI]

Benzo-Fused Double [7]Carbohelicene: Synthesis, Structures, and Physicochemical Properties

25 Oct 2016 Angewandte Chemie International Edition
Yunbin Hu, Xiao-Ye Wang, Pi-Xian Peng, Xin-Chang Wang, Xiao-Yu Cao, Xinliang Feng, Klaus Mgllen,* and Akimitsu Narita*

A benzo-fused double [7]carbohelicene (D7H) was synthesized through a regioselective cyclodehydrogenation of a tetranaphthyl-p-terphenyl-based precursor. The twisted (D7H-1) and anti-folded (D7H-2) conformers of D7H were separated by recrystallization, and their double helicene structures with overlapping terminal benzene rings were unambiguously elucidated by X-ray crystallography. A record-high isomerization barrier (46.0 kcalmol@1) in double helicenes was estimated based on density functional theory (DFT) calculation, which resulted in the excellent conformational stability of D7H. The physicochemical properties of D7H-1 and D7H-2 were investigated by UV/Vis absorption spectroscopy and cyclic voltammetry, displaying the variation of electronic structure upon conformational changes. The optical resolution of the racemic D7H-1 was carried out by chiral HPLC, offering enantiopure D7H-1-(P,P) and D7H-1-(M,M), which were further characterized by circular dichroism spectroscopy.

[full-text][SI]

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