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Assembly of Supramolecular Nanotubes from Molecular Triangles and 1,2-Dihalohydrocarbons

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posted on 26.11.2014, 00:00 by Zhichang Liu, Guoliang Liu, Yilei Wu, Dennis Cao, Junling Sun, Severin T. Schneebeli, Majed S. Nassar, Chad A. Mirkin, J. Fraser Stoddart
Precise control of molecular assembly is a challenging goal facing supramolecular chemists. Herein, we report the highly specific assembly of a range of supramolecular nanotubes from the enantiomeric triangular naphthalene­di­imide-based macrocycles (RRRRRR)- and (SSSSSS)-NDI‑Δ and a class of similar solvents, namely, the 1,2-dihalo-ethanes and -ethenes (DXEs). Three kinds of supramolecular nanotubes are formed from the columnar stacking of NDI‑Δ units with a 60° mutual rotation angle as a result of cooperative [C–H···O] interactions, directing interactions of the [X···X]-bonded DXE chains inside the nanotubes and lateral [X···π] or [π···π] interactions. They include (i) semiflexible infinite nanotubes formed in the gel state from NDI‑Δ and (E)-1,2-dichloroethene, (ii) rigid infinite nonhelical nanotubes produced in the solid state from NDI‑Δ and BrCH2CH2Br, ClCH2CH2Br, and ClCH2CH2I, and (iii) a pair of rigid tetrameric, enantiomeric single-handed (P)- and (M)-helical nanotubes formed in the solid state from the corresponding (RRRRRR)- and (SSSSSS)-NDI‑Δ with ClCH2CH2Cl. In case (i), only the electron-rich CC double bond of (E)-1,2-dichloroethene facilitates the gelation of NDI‑Δ. In cases (ii) and (iii), the lengths of anti-DXEs determine the translation of the chirality of NDI‑Δ into the helicity of nanotubes. Only ClCH2CH2Cl induces single-handed helicity into the nanotubes. The subtle interplay of noncovalent bonding interactions, resulting from the tiny structural variations involving the DXE guests, is responsible for the diverse and highly specific assembly of NDI‑Δ. This research highlights the critical role that guests play in constructing assembled superstructures of hosts and offers a novel approach to creating supramolecular nanotubes.