Fullerene Radical Anion Research Articles

C60 solid state rotational dynamics and production and EPR spectroscopy of fullerenes containing metal atoms

The narrow single-line NMR spectrum of solid C60 at ambient temperature demonstrates that the molecules rapidly reorient within the crystal lattice. The rate of this motion can be quantitatively probed using solid-state NMR by measuring the relaxation rate, 1/T1. The dominant contribution to this rate at ambient temperature arises from the combination of rotation and chemical shift anisotropy (CSA). The contribution, 1/T1CSA, is isolated by measuring the magnetic field dependence of T1, allowing the molecular reorientational correlation time, tau , to be determined from T1CSA and the CSA tensor components. At 283 K tau =9.1 ps, only three times longer than the calculated tau for free rotation, and shorter than the value measured for C60 in solution (15.5 ps). This tau corresponds to a rotational diffusion constant D=1.8*1010 s-1. Below 260 K a second phase with a much longer reorientation time is observed, consistent with reports of an orientational phase transition in solid C60. In both phases tau shows Arrhenius behaviour with apparent activation energies of 1.4 and 4.2 kcal mol-1 for the high-temperature (rotator) and low-temperature (ratchet) phases, respectively. The authors succeeded in producing quantities of fullerene cages containing metal atoms sufficient to allow the first characterization of such a species by electron spin resonance spectroscopy. The EPR spectrum of La@C82 shows an octet of lines centered in the region characteristic of fullerene anion radicals, with a small hyperfine splitting which indicates that the spin is predominantly associated with the carbon shell, leaving the lanthanum atom in its preferred +3 oxidation state.

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.

Near-infrared absorption spectra of fullerene (C60) radical cations and anions prepared simultaneously in solid argon

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTNear-infrared absorption spectra of fullerene (C60) radical cations and anions prepared simultaneously in solid argonZbigniew Gasyna, Lester Andrews, and Paul N. SchatzCite this: J. Phys. Chem. 1992, 96, 4, 1525–1527Publication Date (Print):February 1, 1992Publication History Published online1 May 2002Published inissue 1 February 1992https://doi.org/10.1021/j100183a005RIGHTS & PERMISSIONSArticle Views907Altmetric-Citations108LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (420 KB) Get e-Alerts

Production and Characterization of Metal-Encapsulated Fullerenes

ABSTRACTWe report here the arc-production and spectroscopic characterization of fullerene-encapsulated metal atoms and metal-atom clusters. In particular, both solution and solid-stateelectron paramagnetic resonance (EPR) spectra of LaC82', YC82', SCC82' and Sc3 C82 have been obtained. Additional species containing rareearth atoms and clusters have been produced. The results suggest, for example, that the three scandium atoms in Sc3C82 form a molecule In the shape of an equilateral triangle — as was previously suggested for Sc3 molecules Isolated In a cryogenic rare-gas matrix. The spectraof the MC82 species (M =La, Y, Sc) exhibit small hyperfine couplings and g-values close to 2, suggesting that they can be described as a +3 metal cations within – 3 fullerene radical anion cages. Sc2C2n species — the most abundant metailofuilerenes In the scandlum-fullerene mass spectrum — are EPR-silent, even though Sc2 is EPR-actlve In a rare-gas matrix at 4.2K. A broader Implication of this work Is that production of macroscopic quantities of metal-containing fullerenes may make possible the fabrication of exotic new structures with regular arrays of metal atoms or clusters Isolated in fullerene molecules, resulting in new typesof host/guest nanostructured materials.