Li@C60 as a multi-state molecular switch

R.S. acknowledges financial support from the Scottish Funding Council through SRD-Grant (HR07003). E.E.B.C. gratefully acknowledges Idea International Inc., Sendai, for providing samples of [Li@C60]+(PF6)–. H.J.C. and M.S. acknowledge financial support of EPSRC DTG studentships (EP/M508214/1 and EP/N509644/1, respectively).The field of molecular electronics aims at advancing the miniaturization of electronic devices, by exploiting single molecules to perform the function of individual components. A molecular switch is defined as a molecule that displays stability in two or more states (e.g. “on” and “off” involving conductance, conformation etc.) and upon application of a controlled external perturbation, electric or otherwise, undergoes a reversible change such that the molecule is altered. Previous work has shown multi-state molecular switches with up to four and six distinct states. Using low temperature scanning tunnelling microscopy and spectroscopy, we report on a multi-state single molecule switch using the endohedral fullerene Li@C60 that displays 14 molecular states which can be statistically accessed. We suggest a switching mechanism that relies on resonant tunnelling via the superatom molecular orbitals (SAMOs) of the fullerene cage as a means of Li activation, thereby bypassing the typical vibronic excitation of the carbon cage that is known to cause molecular decomposition.Publisher PDFPeer reviewe

Roadmap on photonic, electronic and atomic collision physics: I. Light-matter interaction

We publish three Roadmaps on photonic, electronic and atomic collision physics in order to celebrate the 60th anniversary of the ICPEAC conference. In Roadmap I, we focus on the light-matter interaction. In this area, studies of ultrafast electronic and molecular dynamics have been rapidly growing, with the advent of new light sources such as attosecond lasers and x-ray free electron lasers. In parallel, experiments with established synchrotron radiation sources and femtosecond lasers using cutting-edge detection schemes are revealing new scientific insights that have never been exploited. Relevant theories are also being rapidly developed. Target samples for photon-impact experiments are expanding from atoms and small molecules to complex systems such as biomolecules, fullerene, clusters and solids. This Roadmap aims to look back along the road, explaining the development of these fields, and look forward, collecting contributions from twenty leading groups from the field

Coalescence reactions of fullerenes

The production of fullerene molecules typically involves extreme high-temperature conditions (electric arcs, flames or resistive heating), and the reactive processes involved are poorly understood. Once separated these molecules can undergo several important reactions, including formation of charge-transfer and adduct compounds, and the encapsulation of atoms. Here we present evidence for coalescence reactions between fullerene molecules: mass spectrometric measurements on hot, dense vapours of small fullerenes (C60 and C70) reveal the formation of stable higher fullerenes which are multiples of the initial masses. The heat of coalescence is released through emission of small, even-numbered fragments which, in a very dense vapour, are efficiently captured by other coalesced fullerenes. These findings have implications for the mechanisms of fullerene formation and growth, and may open the way to new synthetic routes to selected higher fullerenes and encapsulation compounds