Synthesis, extraction and electronic structure of Ce@C 2 n

Abstract

In view of the growing interest in endohedral lanthanide fullerenes, Ce, as a typical+ 4 oxidation state lanthanide element, has been systematically studied. The synthesis, extraction and electronic structure of Ce @ C 2 n are investigated. Soot containing Ce@C 2 n was synthesized in high yield by carbonizing CeO 2-containing graphite rods and are back-burning the CeC 2-enriched cathode deposit in a DC arc plasma apparatus. Ce@C 2 n dominated by Ce@C 82, can be efficiently extracted from the insoluble part of the soot after toluene Soxhlet extraction by pyridine at high temperature and high pressure in a closed vessel. About 60% Ce@C 2 n (2n = 82, 80, 78, 76) and 35% Ce@C 82 can be enriched in the pyridine extract. This fact is identified by desorption electron impact mass spectrometry (DEI MS). The electronic structure of Ce@C 2 n is analyzed by using X-ray photoemission spectroscopy (XPS) of pyridine-free film. It is suggested that the encapsulated Ce atom is in a charge state close to+ 3 and was effectively protected from reaction with water and oxygen by the enclosing fullerene cage. Unlike theoretical expectation, the electronic state of Ce@C 82 is formally described as Ce +3@C 3− 82.