Hemicarceplexes Modify the Solubility and Reduction Potentials of C60

Recent advances in supramolecular fullerene chemistry

Fullerene chemistry has come a long way since 1990, when the first bulk production of C60 was reported. In the past decade, progress in supramolecular chemistry has opened some remarkable and previously unexpected opportunities regarding the selective (multiple) functionalization of fullerenes and their (self)assembly into larger structures and frameworks. The purpose of this review article is to provide a comprehensive overview of these recent developments. We describe how macrocycles and cages that bind strongly to C60 can be used to block undesired addition patterns and thus allow the selective preparation of single-isomer addition products. We also discuss how the emergence of highly shape-persistent macrocycles has opened opportunities for the study of photoactive fullerene dyads and triads as well as the preparation of mechanically interlocked compounds. The preparation of two- or three-dimensional fullerene materials is another research area that has seen remarkable progress over the past few years. Due to the rapidly decreasing price of C60 and C70, we believe that these achievements will translate into all fields where fullerenes have traditionally (third-generation solar cells) and more recently been applied (catalysis, spintronics).

Are the Physical Properties of Xe@Cryptophane Complexes Easily Predictable? The Case of syn- and anti-Tris-aza-Cryptophanes

We report the synthesis and optical resolution of C₃-symmetrical tris-aza-cryptophanes anti-3 and syn-4, as well as the study of their interaction with xenon via hyperpolarized ¹²⁹Xe NMR. These molecular cages are close structural analogues of the two well-known cryptophane-A (1; chiral) and cryptophane-B (2; achiral) diastereomers since these new compounds differ only by the presence of three nitrogen atoms grafted onto the same cyclotribenzylene unit. The assignment of their relative (syn vs anti) and absolute configurations was made possible, thanks to the combined use of quantum calculations at the density functional theory level and vibrational circular dichroism spectroscopy. More importantly, our results show that despite the large structural similarities with cryptophane-A (1) and -B (2), these two new compounds show a very different behavior in the presence of xenon in organic solutions. These results demonstrate that prediction of the physical properties of the xenon@cryptophane complexes, only based on structural parameters, remains extremely difficult.

Incarceration of Higher-Order Fullerenes within Cyclotriveratrylene-Based Hemicarcerands Allows Selective Isolation of C76 , C78 , and C84 from a Commercial Fullerene Mixture

Size-complementary cyclotriveratrylene (CTV)-based hosts can incarcerate C₇₆ , C₇₈ , and C₈₄ , thus allowing the selective isolation of these higher-order fullerenes from a commercially available mixture of fullerenes. The hemicarceplexes, formed after the encapsulation of the size-complementary fullerenes within the hosts, are isolated by column chromatography and released at elevated temperature, thereby leading to the isolation of C₇₆ /C₇₈ and C₈₄ in good purities (up to 95 and 88 %, respectively).

Hybrid materials based on ruthenium and fullerene assemblies

This review provides a detailed overview about the synthesis, properties and applications of all ruthenium-fullerene compounds reported within the last 25 years. The incorporation of ruthenium centers into fullerene compounds by organometallic, covalent or non-covalent bonds has led to a broad range of useful hybrid materials. By this approach novel compounds could be generated that feature the electron-donating and electron-accepting character of ruthenium complexes and fullerenes, respectively. Intramolecular interactions between both units could result in new, combined properties that were studied in the spotlight of emerging applications, such as photovoltaics or catalysis.

Stabilization of reactive species by supramolecular encapsulation

This review describes and updated overview of the stabilization of reactive species and reaction intermediates by inclusion in nanocavities provided by covalent- and supra-molecular containers.

Hemicarceplex formation allows ready identification of the isomers of the metallofullerene Sc3N@C80using1H and13C NMR spectroscopy

A cyclotriveratrylene-based molecular cage forms hemicarceplexes that significantly increase the solubility of commercially available Sc₃N@C₈₀in CDCl₃.