Fourier Transform Infrared and Raman Spectroscopic Study of Chromatographically Isolated Li@C₆₀ and Li@C₇₀

Abstract

IR and Raman investigations have been carried out on purified Li@C60 and Li@C70 produced by low-energy ion implantation. The structural interpretations, based on theoretical considerations and comparison of the obtained vibrational spectra with those of different known fullerene oligomers, have shown that neither of the chromatographically isolated endohedral species (Li@C60(70)) correspond to monomeric nonderivatized molecules. We ascribe the two different fractions of Li@C60 to a double-bonded dimer and a trimer, presumably with the shape of closed triangle. The infrared and Raman spectra of the Li@C70 compound are similar to those of (C70)2, and we therefore propose for this species the structure of a double-bonded dimer (Li@C70)2. The IR spectra of the Li@C60 fractions prepared with 6Li and 7Li isotopes are identical except for the position of broad bands at about 450−600 cm-1, originating from vibrational−rotational movement of the Li+ cation inside the carbon cage.

Angle-resolved photoelectron spectroscopy and scanning tunnelling spectroscopy studies of the endohedral fullerene Li@C60

“…5,6 Early experiments on the isolated material showed the considerably higher reactivity compared to C 60 with a tendency for the purified material to oligomerise. 7 Thin films were shown to exhibit metallic conductivity if kept under high vacuum conditions. 8 More recently, the production of Li@C 60 has been upscaled and commercialised by using a related plasma implantation technique.…”

Progress in classical and quantum variational principles

“…Early theoretical work focussed on the prediction of infrared and Raman [53,54] and neutron scattering [49] spectra due to the motion of X = He, Li + , Na + , K + and CO inside the near-spherical C 60 cage. The predictions of [53] were subsequently confirmed experimentally [55,56] for the infrared bands of Li + @C 60 . Confirmation of the predicted Raman bands [53] of Li + @C 60 is tentative [56].…”

“…The predictions of [53] were subsequently confirmed experimentally [55,56] for the infrared bands of Li + @C 60 . Confirmation of the predicted Raman bands [53] of Li + @C 60 is tentative [56]. Later the theoretical studies were extended to study the dynamics and spectra of atoms, molecules and ions trapped in nonspherical cages, e.g.…”

Doping of C60 Fullerene Peapods with Lithium Vapor: Raman Spectroscopic and Spectroelectrochemical Studies

“…[28] As the interactions of lithium with both SWCNTs and the fullerenes inside the nanotubes are strong due to the small ionic radius and the special properties of the lithiumÀcarbon bond, [10,29] they could be similar to those in fullerenes prepared by the bombardment of C 60 by lithium. [29] In situ spectroelectrochemistry: The Raman spectra of lithium-doped peapods after water treatment indicated residual doping. For potassium-doped peapods it has been shown that it is possible to "de-dope" a sample by applying anodic electrochemical charging.…”