Pyramidal Structures of Lanthanide-C₆₀ Clusters (Ln_n(C₆₀)_m: Ln = Eu and Ho)

Novel lanthanide organometallic clusters, Ln_n(C₆₀)_m, consisting of lanthanide atoms (Ln; Ln = Eu and Ho) and C₆₀ molecules were produced in gas phase by a two-laser vaporization method. The Ln_n(C₆₀)_m clusters were produced predominantly at compositions of (n, m) = (n, n + 3) [n = 1-4]. These stoichiometries showed no chemisorption reactivity toward CCl₄ and O₂ reactants. The cluster having (1,4) composition is proposed to form a tetrahedral structure, in which a Ln atom is surrounded by four C₆₀ molecules. In larger clusters with (n, n + 3) composition, each Ln atom is found in a local (1,4) group. Together with the results of sequential chemisorption of Cl atoms on cluster cations, photoelectron spectroscopy of cluster anions leads us to conclude that Ln₁(C₆₀)_m clusters are charge-transfer complexes expressed as Ln₁^x+(C₆₀)_m^x-, and that Eu and Ho atoms exist as Eu²⁺ and Ho³⁺ ions, respectively.