Since fullerenes are available in macroscopic quantities from fullerene soot, large efforts have been geared toward designing efficient strategies to obtain highly pure fullerenes, which can be subsequently applied in multiple research fields. Here we present a supramolecular nanocage synthesized by metal-directed self-assembly, which encapsulates fullerenes of different sizes. Direct experimental evidence is provided for the 1:1 encapsulation of C 60 , C 70 , C 76 , C 78 and C 84 , and solid state structures for the host-guest adducts with C 60 and C 70 have been obtained using X-ray synchrotron radiation. Furthermore, we design a washingbased strategy to exclusively extract pure C 60 from a solid sample of cage charged with a mixture of fullerenes. These results showcase an attractive methodology to selectively extract C 60 from fullerene mixtures, providing a platform to design tuned cages for selective extraction of higher fullerenes. The solid-phase fullerene encapsulation and liberation represent a twist in host-guest chemistry for molecular nanocage structures.

Regio- and enantioselective hydroformylation of styrenes is attained upon embedding a chiral Rh complex in a nonchiral supramolecular cage formed from coordination-driven self-assembly of macrocyclic dipalladium complexes and tetracarboxylate zinc porphyrins. The resulting supramolecular catalyst converts styrene derivatives into aldehyde products with much higher chiral induction in comparison to the nonencapsulated Rh catalyst. Spectroscopic analysis shows that encapsulation does not change the electronic properties of the catalyst nor its first coordination sphere. Instead, enhanced enantioselectivity is rationalized by the modification of the second coordination sphere occurring upon catalyst inclusion inside the cage, being one of the few examples in achieving an enantioselective outcome via indirect through-space control of the chirality around the catalyst center. This effect resembles those taking place in enzymatic sites, where structural constraints imposed by the enzyme cavity can impart stereoselectivities that cannot be attained in bulk. These results are a showcase for the future development of asymmetric catalysis by using size-tunable supramolecular capsules.

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Fullerene extracts are easily available from fullerene soot, but finding an efficient strategy to obtain them in pure form remains elusive, especially for higher fullerenes (Cx, x > 70). The properties of the latter remain unclear and their potential application to multiple research fields has not been developed mainly due to their purification difficulties. In this Tutorial Review we cover the use of molecular receptors for the separation of fullerenes by means of host-guest interactions. This strategy allows gaining selectivity, no specialized equipment is required and, ideally, recyclable systems can be designed. We focus on the metallosupramolecular receptors using the metal-ligand coordination approach, which offers a controlled and versatile strategy to design fullerene hosts, and the latest strategies to release the fullerene guest will be described. The field is probably in its beginnings but it is rapidly evolving and we are confident that this tutorial review will help researchers to rapidly gain a general overview of the main works and concepts that are leading this promising strategy and that may lead towards a useful methodology to purify fullerenes.

An unprecedented and straightforward supramolecular mask strategy to prepare exclusively equatorial bis-, tris-, and tetrakis-cyclopropanated-C 60 Bingel-Hirsch derivatives is reported. By taking advantage of the high affinity for fullerene of tetragonal prismatic supramolecular cages, a highly stable C 60 31a$(BArF) 8 hostguest complex is submitted to Bingel-Hirsch cyclopropanation reaction conditions. Regioselectivity is strictly dictated by the four cross-shaped apertures of the nanocapsule in a controlled fashion. Moreover, stepwise-cyclopropanated adducts up to tetrakis additions are obtained in excellent yields and purities.

Supramolecular nanocapsule 1⋅(BArF) is able to sequentially and selectively entrap recently discovered U @C and unprecedented Sc CU@C , simply by soaking crystals of 1⋅(BArF) in a toluene solution of arc-produced soot. These species, selectively and stepwise absorbed by 1⋅(BArF) , are easily released, obtaining highly pure fractions of U @C and Sc CU@C in one step. Sc CU@C represents the first example of a mixed metal actinide-based endohedral metallofullerene (EMF). Remarkably, the host-guest studies revealed that 1⋅(BArF) is able to discriminate EMFs with the same carbon cage but with different encapsulated cluster and computational studies provide support for these observations.

A novel naphthalene-based 5·(BArF)8 capsule allows for the size-selective inclusion of C60 from fullerene mixtures. Additionally, 5·(BArF)8 encapsulates C60-derivatives such as C60-PCBM and N-methyl-pyrrolidine-C60.

The metal-directed supramolecular synthetic approach has paved the way for the development of functional nanosized molecules. In this work, we report the preparation of the new nanocapsule 3-(CF3SO3)8 with a A4B2 tetragonal prismatic geometry, where A corresponds to the dipalladium hexaazamacrocyclic complex Pd-1, and B corresponds to the tetraanionic form of palladium 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (2). The large void space of the inner cavity and the supramolecular affinity for guest molecules towards porphyrin-based hosts converts this nanoscale molecular 3D structure into a good candidate for host–guest chemistry. The interaction between this nanocage and different guest molecules has been studied by means of NMR, UV/Vis, ESI-MS, and DOSY experiments, from which highly selective molecular recognition has been found for anionic, planar-shaped π guests with association constants (Ka) higher than 109 m−1, in front of non-interacting aromatic neutral or cationic substrates. DFT theoretical calculations provided insights to further understand this strong interaction. Nanocage 3⋅(CF3SO3)8 can not only strongly host one single molecule of M(dithiolene)2 complexes (M=Au, Pt, Pd, and Ni), but also can finely tune their optical and redox properties. The very simple synthesis of both the supramolecular cage and the building blocks represents a step forward for the development of polyfunctional supramolecular nanovessels, which offer multiple applications as sensors or nanoreactorsWe are grateful for financial support from the MICINN of Spain (CTQ2009-08464/BQU to M. C., CTQ2011-25086/BQU, CTQ2011-23156/BQU, PhD grant AP2010-2517 to M. G. B, INNPLANTA- INP-2011-0059PCT-420000-ACT1 and Consolider-Ingenio CSD2010-00065), the FEDER fund (European Fund for Regional Development) for the grant UNGI08-4E-003, the European Research Council for Project ERC-2011StG-277801 to X. R. and ERC-2008-StG-29910 to M. C., and the Generalitat de Catalunya (2009SGR637, 2009SGR528, and a Ph.D. grant to C. G. S.). X. R. and M. C. thank ICREA-Academia awards. I. I. thanks MINECO for a Ramon y Cajal contract. We thank Dr. Teodor Parella for fruitful discussions. We thank STR's from UdG for technical support, and we also acknowledge the computer resources, technical expertise, and assistance provided by the Barcelona Supercomputing Center Centro Nacional de Supercomputacion, and Centre de Serveis Cientifics i Academics de Catalunya (CESCA) for partial funding of computer tim