TY - JOUR
T1 - Enforced Tubular Assembly of Electronically Different Hexakis(m-Phenylene Ethynylene) Macrocycles
T2 - Persistent Columnar Stacking Driven by Multiple Hydrogen-Bonding Interactions
AU - Zhong, Yulong
AU - Yang, Yi
AU - Shen, Yi
AU - Xu, Wenwu
AU - Wang, Qiuhua
AU - Connor, Alan L.
AU - Zhou, Xibin
AU - He, Lan
AU - Zeng, Xiao Cheng
AU - Shao, Zhifeng
AU - Lu, Zhong Lin
AU - Gong, Bing
N1 - Funding Information:
We thank the Natural Science Foundation of China (Grants 11374207, 21272274, 21372032, 81627801, and 91227109) and the U.S. National Science Foundation (CHE-1306326) for support.
Publisher Copyright:
© 2017 American Chemical Society.
PY - 2017/11/8
Y1 - 2017/11/8
N2 - Hexakis(m-phenylene ethynylene) (m-PE) macrocycles 1-4, sharing the same hydrogen-bonding side chains but having backbones of different electronic properties, are designed to probe the effectiveness of multiple H-bonding interactions in enforcing columnar assemblies. 1H NMR, absorption, fluorescence, and circular dichroism (CD) spectroscopy indicate that, compared with analogous macrocycles that self-associate based on aromatic stacking which is highly sensitive to the electronic nature of the macrocyclic backbones, macrocycles 1-4 all exhibit strong aggregation down to the micromolar (μM) concentrations in nonpolar solvents. Increasing solvent polarity quickly weakens aggregation. In THF and DMF, the macrocycles exist as free molecules. The observed solvent effects, along with the behavior of 5-F6 that cannot self-associate via H-bonding, confirm that H-bonding plays the dominating role in driving the self-association of 1-4. The backbone electronic nature does not change the self-assembling pattern common to 1-4. Fluorescence and CD spectra confirm that macrocycles 1-4 assemble anisotropically, forming helical stacks in which adjacent molecules undergo relative rotation to place individual benzene residues in the favorable offset fashion. Columnar alignment of 1-4 is confirmed by atomic force microscopy (AFM), which resolves single tubes consisting of stacked macrocycles. In addition, macrocycles with backbones of different electronic properties are found to undergo heteroassociation, forming hybrid nanotubes. This study has demonstrated the generality of enforcing the alignment of shape-persistent macrocycles, which represents an invaluable addition to the small number of known tubular stacks capable of accommodating structurally varied molecular components and provides self-assembling nanotubes with inner pores allowing ready structural and functional modification.
AB - Hexakis(m-phenylene ethynylene) (m-PE) macrocycles 1-4, sharing the same hydrogen-bonding side chains but having backbones of different electronic properties, are designed to probe the effectiveness of multiple H-bonding interactions in enforcing columnar assemblies. 1H NMR, absorption, fluorescence, and circular dichroism (CD) spectroscopy indicate that, compared with analogous macrocycles that self-associate based on aromatic stacking which is highly sensitive to the electronic nature of the macrocyclic backbones, macrocycles 1-4 all exhibit strong aggregation down to the micromolar (μM) concentrations in nonpolar solvents. Increasing solvent polarity quickly weakens aggregation. In THF and DMF, the macrocycles exist as free molecules. The observed solvent effects, along with the behavior of 5-F6 that cannot self-associate via H-bonding, confirm that H-bonding plays the dominating role in driving the self-association of 1-4. The backbone electronic nature does not change the self-assembling pattern common to 1-4. Fluorescence and CD spectra confirm that macrocycles 1-4 assemble anisotropically, forming helical stacks in which adjacent molecules undergo relative rotation to place individual benzene residues in the favorable offset fashion. Columnar alignment of 1-4 is confirmed by atomic force microscopy (AFM), which resolves single tubes consisting of stacked macrocycles. In addition, macrocycles with backbones of different electronic properties are found to undergo heteroassociation, forming hybrid nanotubes. This study has demonstrated the generality of enforcing the alignment of shape-persistent macrocycles, which represents an invaluable addition to the small number of known tubular stacks capable of accommodating structurally varied molecular components and provides self-assembling nanotubes with inner pores allowing ready structural and functional modification.
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U2 - 10.1021/jacs.7b09647
DO - 10.1021/jacs.7b09647
M3 - Article
C2 - 29041774
AN - SCOPUS:85033217449
VL - 139
SP - 15950
EP - 15957
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 44
ER -