Synthesis and Isolation of the Titanium-Scandium Endohedral Fullerenes-Sc2 TiC@Ih -C80 , Sc2 TiC@D5h -C80 and Sc2 TiC2 @Ih -C80 : Metal Size Tuning of the Ti(IV) /Ti(III) Redox Potentials

Katrin Junghans; Kamran B Ghiassi; Nataliya A Samoylova; Qingming Deng; Marco Rosenkranz; Marilyn M Olmstead; Alan L Balch; Alexey A Popov

doi:10.1002/chem.201601655

Synthesis and Isolation of the Titanium-Scandium Endohedral Fullerenes-Sc2 TiC@Ih -C80 , Sc2 TiC@D5h -C80 and Sc2 TiC2 @Ih -C80 : Metal Size Tuning of the Ti(IV) /Ti(III) Redox Potentials

Chemistry. 2016 Sep 5;22(37):13098-107. doi: 10.1002/chem.201601655. Epub 2016 Jul 26.

Authors

Katrin Junghans¹, Kamran B Ghiassi², Nataliya A Samoylova¹, Qingming Deng¹, Marco Rosenkranz¹, Marilyn M Olmstead³, Alan L Balch⁴, Alexey A Popov⁵

Affiliations

¹ Leibniz Institute for Solid State and Materials Research (IFW Dresden), Helmholtzstraße 20, 01069, Dresden, Germany.
² Department of Chemistry, University of California, Davis, 95616, USA.
³ Department of Chemistry, University of California, Davis, 95616, USA. mmolmstead@ucdavis.edu.
⁴ Department of Chemistry, University of California, Davis, 95616, USA. albalch@ucdavis.edu.
⁵ Leibniz Institute for Solid State and Materials Research (IFW Dresden), Helmholtzstraße 20, 01069, Dresden, Germany. a.popov@ifw-dresden.de.

Abstract

The formation of endohedral metallofullerenes (EMFs) in an electric arc is reported for the mixed-metal Sc-Ti system utilizing methane as a reactive gas. Comparison of these results with those from the Sc/CH4 and Ti/CH4 systems as well as syntheses without methane revealed a strong mutual influence of all key components on the product distribution. Whereas a methane atmosphere alone suppresses the formation of empty cage fullerenes, the Ti/CH4 system forms mainly empty cage fullerenes. In contrast, the main fullerene products in the Sc/CH4 system are Sc4 C2 @C80 (the most abundant EMF from this synthesis), Sc3 C2 @C80 , isomers of Sc2 C2 @C82 , and the family Sc2 C2 n (2 n=74, 76, 82, 86, 90, etc.), as well as Sc3 CH@C80 . The Sc-Ti/CH4 system produces the mixed-metal Sc2 TiC@C2 n (2 n=68, 78, 80) and Sc2 TiC2 @C2 n (2 n=80) clusterfullerene families. The molecular structures of the new, transition-metal-containing endohedral fullerenes, Sc2 TiC@Ih -C80 , Sc2 TiC@D5h -C80 , and Sc2 TiC2 @Ih -C80 , were characterized by NMR spectroscopy. The structure of Sc2 TiC@Ih -C80 was also determined by single-crystal X-ray diffraction, which demonstrated the presence of a short Ti=C double bond. Both Sc2 TiC- and Sc2 TiC2 -containing clusterfullerenes have Ti-localized LUMOs. Encapsulation of the redox-active Ti ion inside the fullerene cage enables analysis of the cluster-cage strain in the endohedral fullerenes through electrochemical measurements.

Keywords: fullerenes; methane; mixed-metal compounds; scandium; titanium.

Grants and funding

648295/ERC_/European Research Council/International