A Bottom-Up Approach to Solution-Processed, Atomically Precise Graphitic Cylinders on Graphite

Abstract

Extended carbon nanostructures, such as carbon nanotubes (CNTs), exhibit remarkable properties but are difficult to synthesize uniformly. Herein, we present a new class of carbon nanomaterials constructed via the bottomup self-assembly of cylindrical, atomically precise small molecules. Guided by supramolecular design principles and circle packing theory, we have designed and synthesized a fluorinated nanohoop that, in the solid state, self-assembles into nanotube-like arrays with channel diameters of precisely 1.63 nm. A mild solution-casting technique is then used to construct vertical "forests" of these arrays on a highly ordered pyrolytic graphite (HOPG) surface through epitaxial growth. Furthermore, we show that a basic property of nanohoops, fluorescence, is readily transferred to the bulk phase, implying that the properties of these materials can be directly altered via precise functionalization of their nanohoop building blocks. The strategy presented is expected to have broader applications in the development of new graphitic nanomaterials with π-rich cavities reminiscent of CNTs.

The Supramolecular Chemistry of Strained Carbon Nanohoops

“…In aremarkable case of crystal engineering,Jasti, Alemµn, and co-workers designed the larger,f luorinated nanohoop 12F- [12]CPP (Figure 15 b) which, thanks to self-complementary fluorine-hydrogen interactions and am ild solutioncasting technique,s elf-assembled into hexagonally packed bundles of supramolecular nanotubes that are reminiscent of SWCNTs. [136] Atotal of 36 CÀH···F bonds per macrocycle was observed in the crystal packing of 12F- [12]CPP,w ith HÀF distances ranging from 2.53 to 2.62 (sum of van der Waals radii:2 .67 ). Thes olid-state packing also revealed welldefined arene-perfluoroarene interactions between vertical columns,t hereby resulting in an ideal 2D hexagonal circle packing morphology.W henasolution of 12F- [12]CPP in chloroform was drop-casted onto ah ighly oriented pyrolytic graphite (HOPG) substrate," forests" of hexagonal crystalline structures were observed by optical and scanning electron microscopy (SEM;F igure 15 b, bottom).…”

“…In a remarkable case of crystal engineering, Jasti, Alemán, and co‐workers designed the larger, fluorinated nanohoop 12F‐[12]CPP (Figure b) which, thanks to self‐complementary fluorine–hydrogen interactions and a mild solution‐casting technique, self‐assembled into hexagonally packed bundles of supramolecular nanotubes that are reminiscent of SWCNTs . A total of 36 C−H⋅⋅⋅F bonds per macrocycle was observed in the crystal packing of 12F‐[12]CPP , with H−F distances ranging from 2.53 to 2.62 Å (sum of van der Waals radii: 2.67 Å).…”

“…b) Self-assembly of 12F- [12]CPP into noncovalentn anotubesinthe solid state, adapted from Ref. [136] with permission from the American ChemicalS ociety,C opyright (2018).…”

Supramolekulare Chemie von gespannten Kohlenstoffnanoreifen

“…b) 12F‐[12]CPP zeigt nicht‐kovalente Selbstorganisation im Festkörper, übernommen aus Lit. mit der Genehmigung der American Chemical Society, Copyright (2018).…”

“…In einem bemerkenswerten Fall des Kristalldesigns entwarfen Jasti, Alemán und Mitarbeiter den größeren, fluorierten Nanoreifen 12F‐[12]CPP (Abbildung b), der dank selbstkomplementärer Fluor‐Wasserstoff‐Wechselwirkungen und einer milden Lösungsabscheidungstechnik zu hexagonal gepackten Bündeln von supramolekularen Nanoröhren, ähnlich den SWCNTs, zusammengefügt wurde …”