Chiral separation and characterization of triazatruxene-based face-rotating polyhedra: the role of non-covalent facial interactions

15 Mar 2018 Chemical Communications
Pei Zhang, Xinchang Wang, Wei Xuan, Pixian Peng, Zhihao Li, Ruqiang Lu, Shuang Wu, Zhongqun Tian and Xiaoyu Cao *

We constructed a series of novel chiral molecular face-rotating polyhedra (FRP) from two 10,15-dihydro-5H-diindolo[3,2-a:30,20-c]-carbazole (triazatruxene) derivatives and trans-1,2-cyclohexane diamine, and investigated how facial interactions and the positions of substituents determine the diastereoselectivity and geometry of the final assemblies.

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Chiral molecular face-rotating sandwich structures constructed through restricting the phenyl flipping of tetraphenylethylene

31 Jul 2018 Chemical Science
Hang Qu, Xiao Tang, Xinchang Wang, Zhihao Li, Zheyu Huang, Hui Zhang, Zhongqun Tian and Xiaoyu Cao *

Chiral tetraphenylethylene (TPE) derivatives have great potential in chiral recognition and circularly polarized luminescence. However, they were mainly constructed through introducing chiral substituents at the periphery of the TPE moiety, which required additional chemical modifications and limited the variety of chiralities of products. Herein, we constructed a series of chiral face-rotating sandwich structures (FRSs) through restricting the phenyl flipping of TPE without introducing any chiral substituents. In FRSs, the complex arrangements of TPE motifs resulted in a variety of chiralities. We also found that non-covalent repulsive interactions in vertices caused the facial hetero-directionality of FRSs, and the hydrogen bonds between imine bonds and hydroxy groups induced excited-state intramolecular proton transfer (ESIPT) emission of FRSs. In addition, the fluorescence intensity of FRSs decreases with the addition of trifluoroacetic acid. This study provides new insights into the rational design of chiral assemblies from aggregation-induced emission (AIE) active building blocks through restriction of intramolecular rotation (RIR).

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Cocrystallization of Imide-Fused Corannulene Derivatives and C60: Guest-Induced Conformational Switching and 1:1 Segregated Packing

2 Aug 2018 Asian Chemical Editorial Society
Ru-Qiang Lu, Shuang Wu, Yue-Hua Bao, Lin-Lin Yang, Hang Qu, Mithu Saha, Xiao-Ye Wang, You-Zhen Zhuo, Binbin Xu, Jian Pei, Hui Zhang, Wengui Weng, and Xiao-Yu Cao*

A pair of interconvertible stereoisomers of imidefused corannulene derivatives was mixed with C60, which resulted in cocrystallization into a 1:1 segregated packing motif through concave–convex p–p interactions. Only one conformation was observed in the cocrystal owing to guestinduced conformational switching. The 1D assemblies of the complex showed promising applications in organic electronics.

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Impacts of Stereoisomerism on Molecular Packing and Charge Transport of Imide-Fused Corannulene Derivatives

23 Mar 2018 Cryst. Growth Des
Ru-Qiang Lu, Yuxiu Liu, Shuang Wu, Mithu Saha, Hang Qu, Rui Chen, Lin-Lin Yang, Xiao-Ye Wang, Yuchen Wang, Wengui Weng, Yi Zhao,* and Xiaoyu Cao*

Two chiral tertiary carbon centers bearing one mesityl group at each center are introduced into the molecular backbone of imide-fused corannulene derivatives to produce four stereoisomers (i.e., (S, S), (R, R), (R, S), or (S, R) configurations on two chiral carbons) in one pot, which are separated into two portions through column chromatography over silica gel. Portion 1, containing a pair of enantiomers ((S, S) and (R, R)), adopts layered packing in the crystal. Portion 2, consisting of a pair of mesomers ((R, S) and (S, R)), exhibits columnar packing in their cocrystal. Theoretical calculations are performed on these two packing motifs, revealing that Portion 1 displays hole-dominated transport, whereas Portion 2 shows electron-dominated transport.

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Novel Triindolo-Truxene Derivatives: Design, Synthesis, and FineTuning of Electronic Properties and Molecular Assembly through Molecular Engineering

10.1002/chem.201804457 Chem. Eur. J.
Jun-Bo Chen, Cen Zhou, Ru-Qiang Lu, Xin-Chang Wang, Hang Qu, Mithu Saha, Hao-Liang Liu, Hui Zhang and Xiao-Yu Cao*

Triindolo-truxene, a C3-symmetric molecule with a large π-conjugated plane, has six methylene carbon atoms and three aromatic carbon atoms which can be facilely functionalized. Herein, we introduce butyl, carbonyl, cyano, and/or malononitrile groups into six methylene carbon atoms (6-, 14-, 22-, or 8-, 16-, 24-positions) and/or three aromatic carbon atoms (2-, 10-, and 18-positions) of triindolo-truxene to produce eight derivatives. Their photophysical and electrochemical properties, and molecular assembly can be effectively modulated by substituents and substitution patterns. Incorporation of electron-deficient groups led to red shifts in both the absorption and the emission of these derivatives, and also lowered their HOMO and LUMO levels. Different substitution patterns resulted in the different intramolecular donor-acceptor interactions. The substitutions of electron-deficient groups at 6-, 14-, and 22-ethylene carbon atoms led to the intramolecular charge transfer from the fluorene arms to the truxene core, whereas the corresponding substitutions at 8-, 16-, and 24-methylene carbon atoms resulted in the converse intramolecular charge transfer from the truxene core to the fluorene arms. Their molecular packing in single crystals and molecular aggregation in solutions are also manipulated by their substituents and substitution patterns. This work provides a straightforward strategy to alter the properties of triindolo-truxene.

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Probing the kinetics in supramolecular chemistry and molecular assembly by microfluidic-NMR spectroscopy

25 Apr 2018 Sci China Chem
Hongxun Fang, Yibin Sun, Xinchang Wang, Manvendra Sharma, Zhong Chen, Xiaoyu Cao*, Marcel Utz* and Zhongqun Tian*

Microfluidic-NMR spectroscopy has been extended to study the kinetics in supramolecular chemistry and molecular assembly. Kinetics of a multicomponent host-guest supramolecular system containing viologen derivatives, β-cyclodextrins and cucurbit [7]urils are studied by a PMMA based microfluidic chip combined with a dedicated transmission line probe for NMR detection. By combining microfluidic technology with NMR spectroscopy, the amount of material required for a full kinetic study could be minimized. This is crucial in supramolecular chemistry, which often involves highly sophisticated and synthetically costly building blocks. The small size of the microfluidic structure is crucial in bringing the time scale for kinetic monitoring down to seconds. At the same time, the transmission line NMR probe provides sufficient sensitivity to work at low (2 mM) concentrations.

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