Lanthanum complexes of spheroidal carbon shells

Scandium Clusters in Fullerene Cages

The production and spectroscopic characterization of fullerene-encapsulated metal-atom clusters is reported. In particular, both solution and solid-state electron paramagnetic resonance (EPR) spectra of Sc(3)C(82) have been obtained. ScC(82) also gives an EPR spectrum, but Sc2Cn species-the most abundant metallofullerenes in the mass spectrum-are EPR-silent even though Sc(2) is EPR-active in a rare-gas matrix at 4.2 K. The results suggest that the three scandium atoms in Sc(3)C(82) form an equilateral triangle-as was previously suggested for Sc(3) molecules isolated in a cryogenic rare-gas matrix. The spectrum of ScC(82) has features similar to those found earlier for LaC(82) and YC(82), suggesting that it can also be described as a +3 metal cation within a -3 fullerene radical anion. An implication of this work is that production of macroscopic quantities of clustercontaining fullerenes may make possible the fabrication of exotic new structures with regular arrays of metal-atom clusters isolated in fullerene molecules, resulting in a new type of host/guest nanostructured material.

Mass spectrometry and fullerenes

This article presents, from amass spectrometry perspective, an historical account of research on gas-phase carbon clusters, which has led to the discovery of another form of carbon, fullerenes. In addition, more recent mass spectrometric studies on analysis of fullerene derivatives and synthesis of doped fullerenes are described. The early, strong evidence for certain "magic number" carbon clusters, most notably C60 (buckminsterfullerene), was obtained largely from mass spectrometric experiments. These studies led to the controversial postulation of the soccerball structure for C60, which provoked increased experimental and theoretical efforts. This research eventually resulted in the discovery of a simple method by which large quantities of fullerenes can be produced. The availability of these new, all-carbon molecules has motivated a broad range of synthetic and characterization studies that are expanding at a frenetic pace. Mass spectrometry not only played a critical role in the discovery of fullerenes but also now is crucial for determination of the unusual chemical and physical properties of fullerenes and fullerene-based materials.

Space, Stars, C 60 , and Soot

Although carbon has been subjected to far more study than all other elements put together, the buckminsterfullerene hollow-cage structure, recently proposed to account for the exceptional stability of the C(60) cluster, has shed a totally new and revealing light on several important aspects of carbon's chemical and physical properties that were quite unsuspected and others that were not previously well understood. Most significant is the discovery that C(60) appears to form spontaneously, and this has particularly important implications for particle formation in combustion and in space as well as for the chemistry of polyaromatic compounds. The intriguing revelation that 12 pentagonal "defects" convert a planar hexagonal array of any size into a quasi-icosahedral cage explains why some intrinsically planar materials form quasi-crystalline particles, as appears to occur in the case of soot. Although the novel structural proposal has still to be unequivocally confirmed, this article pays particular attention to the way in which it provides convincing explanations of puzzling observations in several fields, so lending credence to the structure proposed for C(60).

Probing C60

Experiments involving the laser vaporization of graphite have indicated that one particular duster of carbon, C(60), is preeminently stable; this special stability may be evidence that C(60) can readily take the form of a hollow truncated icosahedron (a sort of molecular soccerball). If true, this structure for C(60) would be the first example of a spherical aromatic molecule. In fact, because of symmetry properties unique to the number 60, it may be the most perfecty spherical, edgeless molecule possible. Its rapid formation in condensing carbon vapors and its extreme chemical and photophysical stability may have far-reaching implications in a number of areas, particularly combustion science and astrophysics. For these reasons C(60) and other dusters of carbon have continued to be the subject of intense research. This article provides a short review of the many new experimental probes of the properties of C(60) and related carbon dusters.