Abstract
The structures of hierarchically assembled supramolecular architectures are dictated characteristically by the encoded symmetries and geometries of the corresponding building blocks. In literature, assorted Platonic molecular polyhedra have been built out of highly symmetric macrocycles. Nonetheless, the synthesis of pillararene-based molecular cages remains challenging owing to the underlying shape and limited derivatization strategies of this macrocyclic scaffold. Herein, we report the assembly of AgnL2 metal-organic pillars from rim-differentiated pillar[5]arene-derived ligands, Lm and Lp, through [N···Ag+···N] coordinative bonds. These stereolabile macrocycles undergo chiral self-sorting during complexation. Although the meta-substituted Lm forms diastereoisomeric Ag5Lm2 complexes without stereocontrol in solution, only a meso-Ag4Lm2 complex with a Ag4 kernel was observed in the solid state. In contrast, the narcissistic coassembly of the para-substituted Lp with AgPF6 results in enantiomeric Ag5Lp2 complexes resembling twisted pentagonal prisms. This research paves the way for the construction of deep-cavity metallocavitands and nanochannels with unique molecular recognition and transportation properties.
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•Metal-organic pillar-like nanotubes are built by coordination-driven self-assembly•Stereolabile pillararene-based macrocyclic ligands undergo chiral self-sorting•Templation by anion is essential for the formation of the twisted pentagonal prisms•The tubular structures show enhanced binding toward guests of specific sizes
Nanotubes are attractive structural motifs that have been investigated extensively for a plethora of electronic, mechanical, materials, and biological applications. Nonetheless, fabricating molecular nanotubes with well-defined length, diameter, and handedness remains a challenging topic across different disciplines. Herein, we demonstrate a design strategy to construct such tubular structures, namely metal-organic pillars, by stacking preorganized macrocyclic building blocks with high precision. In particular, pillararene-based ligands with pyridinyl moieties are assembled in a head-to-head fashion in the presence of silver salts through labile [N···Ag+···N] coordinative bonds. These resulting AgnL2 complexes, which are in the shape of twisted pentagonal prisms of circa 2 nm heights, display chiral self-sorting behavior and host-guest properties. Our work provides a blueprint for creating discrete and polymeric nanotubes and 1D channels with much greater complexity and functionality.
Nanotubular molecular cages—namely, metal-organic pillars—have been constructed from pillararene-based building blocks by virtue of multiple [N···Ag+···N] coordination bonds. Depending on the molecular design of the corresponding macrocyclic ligands, the hierarchical self-assembly processes of these metallosupramolecular structures in the shape of twisted prisms can display either social or narcissistic chiral self-sorting in the solid state. Our findings herald a strategy for engineering deep cavitands and one-dimensional nanochannels with well-defined diameter, length, and handedness.