Ratcheting rotation or speedy spinning: EPR and dynamics of Sc3C2@C80. Issue 64 (26th July 2017)

• Record Type: Journal Article
• Authors: Roukala, Juho; Straka, Michal; Taubert, Stefan; Vaara, Juha; Lantto, Perttu
• Is Part Of: Chemical communications. Volume 53:Issue 64(2017)
• Page Start: 8992
• Page End: 8995
• Publication Date: 2017-07-26
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1039/c7cc04695b
• Languages: English
• ISSNs: 1359-7345

Abstract

Abstract : First principles modelling graphically explains how changes in the Sc-trimer motion cause the curious temperature dependence of Sc3 C2 @C80 EPR spectra. Abstract : Besides their technological applications, endohedral fullerenes provide ideal conditions for investigating molecular dynamics in restricted geometries. A representative of this class of systems, Sc3 C2 @C80 displays complex intramolecular dynamics. The motion of the 45 Sc trimer has a remarkable effect on its electron paramagnetic resonance (EPR) spectrum, which changes from a symmetric 22-peak pattern at high temperature to a single broad lineshape at low temperature. The scandium trimer consists of two equivalent and one inequivalent metal atom, due to the carbon dimer rocking through the Sc3 triangle. We demonstrate through first-principles molecular dynamics (MD), EPR parameter tensor averaging, and spectral modelling that, at high temperatures, three-dimensional movement of the enclosed Sc3 C2 moiety takes place, which renders the metal centers equivalent and their magnetic parameters effectively isotropic. In contrast, at low temperatures the dynamics becomes restricted to two dimensions within the equatorial belt of the I h symmetric C80 host fullerene. This restores the inequivalence of the scandium centers and causes their anisotropic hyperfine couplings to broaden the experimental spectrum.