The isolation and electrochemical property of Tb2C90 (I, II) isomers

Abstract

ABSTRACTSoot containing Tb2C90 was synthesized in a modified Krätschmer-Huffman generator by vaporizing the composite graphite rods containing a mixture of Tb4O7 and graphite powder at an atmosphere of 300 torr He. The as-produced soot was collected and refluxed in 1,2,4-trichlorobenzene (TCB) for 12 h. After filtration and distillation to remove TCB, the product was immediately dissolved in toluene, and then subjected to HPLC separation to obtain the two individual isomers of Tb2C90 (I, II), which were confirmed by matrix-assisted laser desorption time-of-flight mass spectrometry and analytical HPLC. According to its UV-Vis-NIR absorption spectrum, the molecular structure of Tb2C90 (II) was estimated to be Tb2C2@Cs(hept)-C88, in which four electrons are transferred from endohedral Tb2C2 carbide cluster to the Cs(hept)-C88 carbon cage. The electrochemical properties of Tb2C90 (I, II) isomers was investigated by cyclic voltammetry. It is found that the first reduction of Tb2C90 (II) is close to that of Tb2C90 (I), whereas its first oxidation potential is larger than that of Tb2C90 (I). Hence, is a better electron acceptor than Tb2C90 (I). Moreover, the electrochemical potential gap of Tb2C90 (II) is larger than that of Tb2C90 (I), which is correlated with the thermodynamic stability and relative abundance of the two isolated Tb2C90 isomers. Through comparative study of Tb2C2@Cs(hept)-C88 and Sc2C2@Cs(hept)-C88, it is concluded that the endohedral dimetallo-carbide cluster has greater effect on the oxidation properties than reduction properties of dimetallo-carbide clusterfullerenes.