Specific and Oriented Encapsulation of Fullerene C₇₀ into a Supramolecular Double‐Decker Cage Composed of Shape‐Persistent Macrocycles

Abstract

An efficient strategy for the specific recognition of ellipsoidal fullerenes uses molecular containers with well-designed three-dimensional (3D) nanospaces. We describe the synthesis of a supramolecular double-decker cage composed of shape-persistent metallomacrocycles and pillar ligands. A discrete 3D nanospace was built within the molecular framework of the shape-persistent-macrocycle/bidentate-pillar molecule. The single-crystal structure of the supramolecular cage reveals a uniquely shaped inner cavity with a size and net volume (>670 Å ) that are well matched to the shape and size of C . The cage exhibited higher selectivity for C over C , the smaller carbon allotrope. We suggest that such C -selective recognition is derived from multiple CH-π interactions between hydrogen atoms inside the cage and C .

Supramolecular Metallacycles and Their Binding of Fullerenes

“…Covalently bondeds ystemsa re quite common, for example,c yclodextrins, cucurbiturils and cryptands which bind cations, [8] anions, [9] or hydrophobic molecules [10] by variation of their peripherald ecoration.T oroidal coordination cages are also able to bind guest molecules and separate fullerenes. [11] These systems are challenging to model using density functionalt heory (DFT) due to their large size. Herein we demonstrate not only that ag eometry-optimized structure of al arge emptym etallacycle can be obtained,b ut also the C 60 and C 70 Figure 1.…”

“…Covalently bonded systems are quite common, for example, cyclodextrins, cucurbiturils and cryptands which bind cations, anions, or hydrophobic molecules by variation of their peripheral decoration. Toroidal coordination cages are also able to bind guest molecules and separate fullerenes …”

Exploration of Nano‐Saturns: A Spectacular Sphere–Ring Supramolecular System

“…We expect that tuning of the electronic density on the interacting hydrogen or other atoms by the introduction of functional groups should influence the association property. Recently, a double‐decker disk‐type ring consisting of dibenzothiophene macrocycles and metal ions was reported by Tanaka et al . This approach is promising to increase the contact sites for CH–π interactions.…”

“…[79] For the complexeso f disk-typer ings, the association constants are not so high because of the narrow contact area. We expect that tuningo ft he electronic density on the interacting hydrogen or other atoms by the introduction of functional groups should influence the association property.R ecently,adouble-decker disk-typer ing consisting of dibenzothiophene macrocycles and metal ions was reported by Ta naka et al [80] This approachi sp romising to increaset he contact sites for CH-p interactions. Some beltshaped rings exhibited high complexation selectivity for C 60 and C 70 ,b ut the selectivity was relativelyl ow for disk-type rings so far reported.…”

Complexation of an Anthracene‐Triptycene Nanocage Host with Fullerene Guests through CH⋅⋅⋅π Contacts

“…Tanaka et al reported a double-decker macrocycle with 32 H atoms directed inward potentially. [11] Another way to realize such a structure is by constructing a cage-type framework so as to surround a guest molecule, which is well known as the cryptate effect in supramolecular chemistry. [12] There are a large number of cage-type hosts that include guest molecules effectively by preorganized multipoint recognition.…”