Putting Rings around Carbon Nanotubes

Abstract

In the last five years, we have developed synthetic methods towards encapsulation of single-walled carbon nanotubes (SWNTs) into organic macrocycles, to form rotaxane-type molecules. These are the first examples of mechanically interlocked SWNT derivatives (MINTs). In this article, the motivation to continue developing the chemistry of SWNTs at a time well past their hype is discussed and our synthetic strategy and characterization methodology is explained in detail, stressing the general aspects. In particular, special emphasis is placed on the importance of adequate control experiments and bulk spectroscopic and analytical data to determine the structure of SWNT derivatives, as opposed to relying only (or mostly) on microscopy. Also our experimental results are used as pretext to reflect on more general/conceptual issues pertaining to the chemistry of SWNTs and mechanically interlocked molecules.

The Supramolecular Chemistry of Strained Carbon Nanohoops

“…Pérez and co‐workers have recently developed a concept for synthesizing mechanically interlocked carbon nanotubes (“ MINTs ”) which is based on “clipping” rings around single‐walled carbon nanotubes ( SWCNTs ) and represents an appealing approach for functionalizing and solution‐processing of these nanomaterials. Ohe and co‐workers have reported a related “ring‐toss” approach, which relies on the spontaneous interaction of π‐conjugated carbon nanohoops (π‐extended derivatives of [8]CPPA , [9]CPPA , and [10]CPPA ) with SWCNTs , which is why the resulting materials are perhaps best described as poly‐pseudorotaxanes .…”

Supramolekulare Chemie von gespannten Kohlenstoffnanoreifen

“…Pérez et al. haben ein Konzept zur Synthese von mechanisch verzahnten Kohlenstoff‐Nanoröhren (mechanically interlocked carbon nanotubes, MINTs) entwickelt, bei dem Ringe um einwandige Kohlenstoff‐Nanoröhren (SWCNTs) zuschnappen (Clipping) und so einen attraktiven Ansatz zur Funktionalisierung dieser Nanomaterialien und deren Bearbeitung in Lösung bieten. Ohe und Mitarbeiter haben einen “Ringe werfen”‐Ansatz entwickelt, bei dem die spontane Wechselwirkung von π‐konjugierten Kohlenstoff‐Nanoreifen (π‐vergrößerte Derivate von [8]CPPA , [9]CPPA und [10]CPPA ) und SWCNTs genutzt wird, wodurch die resultierenden Materialien am besten als Poly‐Pseudorotaxane beschrieben werden können .…”

Carbon Nanostructures in Rotaxane Architectures

“…In recent years, an unexplored alternative for the chemical modification of single‐walled carbon nanotubes (SWCNTs) has been described, in which a macrocycle is threaded by a SWCNT. This approach has allowed the chemical attachment of useful components to the sidewall of SWCNTs, combining the best of covalent and non‐covalent approaches and yielding mechanically interlocked rotaxane‐type CNTs (MINTs) (Figure ) , …”

“…For the successful threading of SWCNTs into the ring shaped macrocycle component (Figure ) one of main requirements is the use of thin SWCNTs, being the most suitable those with diameters around 0.8 and 0.9 nm, diameter that show the (7,6) and (6,5)‐enriched CoMoCAT SWNTs , …”

“…In the first reported synthesis of MINTs, the direct threading of SWCNTs through previously formed macrocycles was considered. However, the results indicated that this threading process was indeed highly unlikely, which was later attributed to the extreme aspect ratio required for the proper encapsulation of SWCNTs into the macrocycle and the tendency of SWCNTs to bundle up …”