Ion mobility studies of metal-coated fullerenes

Abstract

Ion mobility measurements have been used to examine the structures and fragmentation processes of Nb x C 60 + complexes with up to five niobium atoms. Our results confirm the observations of Martin and collaborators that loss of C 3 is an important fragmentation process for complexes with x ≥ 3. However, ion mobility measurements for Nb x C 60 + complexes and their Nb x C 60−3 n + fragments show that they are all fullerenes. It is likely that the Nb x C 60−3 n + fragments with an odd number of carbon atoms are stabilized by a niobium atom occupying the defect site in the fullerene cage, and that this stabilization makes C 3 loss energetically favored over the usual fullerene dissociation process of C 2 loss. Detailed analysis of the ion mobility measurements shows that the niobium atoms in the Nb x C 60 + complexes are clustered together on the fullerene surface. At high injection energies a structural transformation occurs for Nb 2C 60 + and one of the niobium atoms apparently moves to an endohedral position. This process does not occur for NbC 60 +, but an analogous structural transformation appears to occur for all complexes with x > 2.