Wraparound hosts for fullerenes: tailored macrocycles and cages

Custom-made macrocyclic receptors for fullerenes are proving a valuable alternative to achieve the affinity and selectivity required to meet challenges such as the selective extraction of higher fullerenes, their chiral resolution, or the self-assembly of functional molecular materials. In this Minireview, we highlight some of the important breakthroughs that this class of fullerene hosts has already produced.     

Liquid-crystalline hybrid materials based on [60]fullerene and bent-core structures

What a core-ker! By the appropriate combination of promesogenic bent-core structures and the C(60) unit, lamellar polar liquid-crystal phases were induced. The supramolecular organization of the functional fullerene-based assemblies, the temperature range of the soft phase, the stabilization of the mesophase-like order at room temperature, and the molecular switching under an electric field can be tuned, depending on the molecular structure.     

Impact of concentration self-quenching on the charge generation yield of fullerene based donor-bridge-acceptor compounds in the solid state

A fullerene based Donor-Bridge-Acceptor (DBA) compound, incorporating a π-extended tetrathiafulvalene electron donor, is investigated with respect to its photophysics in solution versus solid state. Solid films of neat DBA are compared with blend films where the DBA compound is diluted in the inert, low dielectric, polymer poly(styrene). It is found that the moderate intermolecular electronic coupling and donor-acceptor separation (22 ?) in this case leads to the generation of more dissociated, intermolecular charges than a mixture of the donor and acceptor reference compounds. However, the increased intermolecular interactions in the solid state lead to the excited state of the fullerene suffering from concentration self-quenching. This is found to severely affect the charge generation yield in solid films. The impact of competing intra and intermolecular interactions in the solid state upon the film photophysics is analysed in terms of a kinetic model which includes both the effects of concentration self-quenching and the impact of film composition upon the dielectric stabilisation of charge separated states. We conclude that both concentration self-quenching and dielectric stabilisation are critical in determining the photophysics of the blend films, and discuss strategies based upon our observations to enhance the charge photogeneration properties of organic films and photovoltaic devices based upon DBA compounds.     

Elementary excitations of quantum critical (2+1)-dimensional antiferromagnets

It has been proposed that there are degrees of freedom intrinsic to quantum critical points that can contribute to quantum critical physics. We point out that this conclusion is quite general below the upper critical dimension. We show that in (2+1)D antiferromagnets Skyrmion excitations are stable at criticality and identify them as the critical excitations. We find exact solutions composed of Skyrmion and anti-Skyrmion superpositions, which we call topolons. We include the topolons in the partition function and renormalize by integrating out small size topolons and short wavelength spin waves. We obtain a correlation length exponent nu=0.690 666 and anomalous dimension eta=0.0166.     

New challenges in fullerene chemistry

The aim of this focus article is to emphasize those aspects of fullerene chemistry which currently represent important challenges for the development and future applications of these new carbon allotropes, as well as to celebrate the tenth anniversary of the fullerenes Nobel Prize.