Preferential separation of fullerene[84] from fullerene mixtures by encapsulation

Abstract

The encapsulation of fullerenes with a cyclotriveratrylene derivative, capable to self assemble into a dimer by means of three strong 4-ureidopyrimidinone quadruple hydrogen bonds is described. The system shows preference for C84, allowing its easy enrichment directly from fullerene mixtures.

Molecular basis for the recognition of higher fullerenes into ureidopyrimidinonecyclotriveratrylene self-assembled capsules

“…Our in silico results are crucially supported by experimental data. Indeed, on top of accurately reproducing experimentally observed capsule selectivity towards fullerenes (preference for C84 over C70, and even more over C60), [14][15] our calculations are also able to correctly predict the preferred structural conformation of the 12 capsules as detected by NMR. Selectivity trends found by our calculations and previous experiments are here furthermore reconfirmed by racemization studies featuring CD spectroscopy.…”

“…The specially designed monomers 1 composing such host capsules were based on a cyclotriveratrylene (CTV) core, equipped with three 2-ureido-4-[1H]-pyrimidinone (UPy) moieties each bearing an array of two hydrogen bond donors and two acceptors; this enabled facile dimerization into 12 via hydrogen bonding. The aim of our work, wherein we have observed full agreement between theory and experiment, was to provide an explanation as to why, in previous studies, [14][15] such capsules were experimentally seen to prefer C84 as a guest over C70 and C60.…”

“…For filled homochiral capsules, on the other hand, racemization rates definitely showed dependence on the volume of the included guest: indeed, the enthalpic barrier ΔH ≠ clearly increases with fullerene size, in full agreement with the higher stabilities found by calculations, and the previously determined binding constants. [15] We nonetheless note that, possibly due to the greater rotational frustration suffered by larger fullerenes after encapsulation, the entropic barrier ΔS ≠ is also seen to increase with guest size: as a result, at 298 K, enthalpy-entropy compensation restores free energies of activation (ΔG ≠ ) to more or less similar values.…”

Wirte für Fullerene: maßgeschneiderte Makrocyclen und Käfige

“…B. zur enantioselektiven Extraktion hçherer Fullerene, [40,41] [47] Kürzlich verwendeten auch de Mendoza und Mitarbeiter eine attraktive Strategie zur selektiven Bindung von C 70 und C 84 in einer CTV-Kapsel, die durch Selbstorganisation mittels Wasserstoffbrücken erhalten wurde. [62] Auf eine umgekehrte Weise kçnnen auch Fullerenmoleküle zur Feinabstimmung der Eigenschaften molekularer …”

Self-assembled Cages and Capsules Using Cyclotriveratrylene-type Scaffolds

“…19 Homodimeric capsules of type (2) 2 ¢F, where 2 is a tris(4-ureidopyrimidinone)-appended CTG and F is an encapsulated fullerene, have been reported by de Mendoza and co-workers (Chart 3). 5,20,21 Binding of the fullerene templates the capsule formation in solution. The system is selective for higher fullerenes and a combination of experimental and theoretical studies 5,21 have established that binding constants follow the trend C 90 µ C 84 > C 78 > C 76 > C 70 > C 60 .…”