Isolation and Electrochemical Property of Ho2O@C90 Isomers

Abstract

Four oxide clusterfullerenes Ho2O@C90 (I–IV) were prepared by a modified arc discharge method and isolated by a multistage high performance liquid chromatography procedure. Based on their vis-NIR spectra, the carbon cage symmetries in Ho2O@C90 (I, III, IV) are confirmed to be C 2(43)-C90, C 2(40)-C90 and C 2(41)-C90, respectively. Electrochemical studies display that the first and second reduction potentials of Ho2O@C90 isomers are close to those of Er2C2@C90 ones, but much lower than those of Sm@C90 ones. Moreover, it is found that the electrochemical band gaps of Ho2O@C90 isomers are also very close to those of Er2C2@C90 isomers. A detailed investigation on the redox potentials of C90 based EMFs reveals that endohedral clusters/atoms have much greater effect than carbon cage symmetries on the electrochemical properties of EMFs.