Dimeric Capsules with a Nanoscale Cavity for [60]Fullerene Encapsulation

Abstract

The acid-assisted and guest-induced formation of superstructures was achieved by the addition of haloacetic acids to a toluene solution of the resorcin[4]arene derivatives 1 and [60]fullerenes. The formation of dimeric superstructures that encapsulated a nanosized guest molecule was observed when appropriate acids, such as haloacetic acids, and suitable guest molecules, such as [60]fullerenes, were co-added to a toluene solution of cavitand 1 that has four pyridine units, whereas a complicated equilibrium between several species was detected without [60]fullerenes, and the formation of discrete superstructures was not monitored in the absence of haloacetic acids. The spectroscopic data indicate that the formed [60]fullerene-encapsulated complexes have the structure of 2. These complexes are self-assembled through pyridinium-anion-pyridinium interactions and by pi-pi and van der Waals interactions. The rate of decomplexation of 2 is estimated to be 3.1 s(-1) from a 2D exchange NMR spectrum. The [60]fullerene encapsulation process can be controlled by modifying the amounts of acids used, changing the temperature of the system, altering the ratio of acid/base, and even through varying the solvent polarity. Moreover, the fluorescence spectra show band-narrowing spectral changes and a retardation of the relaxation characteristics of isolated and isotropic [60]fullerenes, which indicates that the environmental change around [60]fullerene is induced upon its encapsulation.

Selective C70 encapsulation by a robust octameric nanospheroid held together by 48 cooperative hydrogen bonds

“…Most of the alternative methods for fullerene separation and purification are only selective towards the major component C 60 49; examples in the literature in which C 70 are preferred are scarce. Although a few examples of C 70 and C 60 fullerenes and receptors have been reported, they were mainly based on the dimeric structures50, or metal-ligand coordinative bonds4951525354. The presented system consist on purely organic and multimembered spheroidal architecture and for reasons of synthetic economy it provides a major advantage since only one molecule is needed to generate selective receptor for fullerenes.…”

Complete Dynamic Reconstruction of C60, C70, and (C59N)2 Encapsulation into an Adaptable Supramolecular Nanocapsule

“…In order to explore in detail the dynamics of fullerene encapsulation, the in–out diffusion of C 60 and C 70 in 1 8+ under equilibrium conditions through 1 H– 1 H exchange spectroscopy (EXSY) experiments was investigated …”

Anion induced capsular self-assemblies

“…Jang, Hong and co-workers were the first to provide evidence that the fullerene encapsulation could be achieved by anion assisted dimeric assembly of pyridyl functionalized resorcin [4]arene 40. 93 Proper selection of guest molecule as well as the proper choice of acid resulted in the fullerene encapsulated supramolecular assembly via pyridine-anion-pyridinium interactions. Acid-assisted and fullerene-induced formation of a dimeric capsular assembly was validated by 1 H NMR experiments.…”