A remarkable mixture of germanium with phosphorus and arsenic atoms making stable pentagonal hetero-prisms [M@GeE], E = P, As and M = Fe, Ru, Os.

A pentagonal hetero-prismatic structural motif was found for singly transition metal doped M@GeE clusters, where the transition metal atom is located at the centre of a (5/5) GeE prism in which Ge is mixed with either P or As atoms. Structural characterization indicates that each (5/5) GeE prism is established by joining of two GeE and GeE strings in a prismatic fashion rather than two Ge and E strings. Each string results from a remarkable mixture of Ge and E atoms and contains only one E-E connection due to the fact that Ge-E bonds are much stronger than E-E connections. From the donor-acceptor perspective, the GeE tube donates electrons to the M center, which behaves as an acceptor. NBO atomic charge and ELI_D analyses demonstrate such electrostatic interactions of the M dopant with a GeE tube which likely induce thermodynamic stability for the resulting M@GeE cluster. CMO analysis illustrates that the conventional 18 electron count is recovered in the M@GeE cations.