Synthesis, Crystal and Electronic Structures, and Magnetic Properties of LiLn 9 Mo 16 O 35 (Ln=La, Ce, Pr, and Nd) Compounds Containing the Original Cluster Mo 16 O 36

The new compounds LiLn 9 Mo 16 O 35 (Ln=La, Ce, Pr, and Nd) were synthesized from stoichiometric mixtures of Li 2 MoO 4 , Ln 2 O 3 , Pr 6 O 11 or CeO 2 , MoO 3 , and Mo heated at 1600 °C for 48 h in a molybdenum crucible sealed under a low argon pressure. The crystal structure, determined from a single crystal of the Nd member, showed that the main building block is the Mo 16 O 36 unit, the Mo 16 core of which is totally new and results from the fusion of two bioctahedral Mo 10 clusters. It can also be viewed as a fragment of an infinite twin chain of edge‐sharing Mo 6 octahedra. The Mo 16 O 36 cluster units share some oxygen atoms to form infinite chains running parallel to the b axis, which are separated by the rare‐earth and lithium cations. 7 Li‐NMR experiments, carried out at high field on the nonmagnetic LiLa 9 Mo 16 O 35 , provided insights into the local environment of the lithium ions. Magnetic susceptibility measurements confirmed the trivalent oxidation state of the magnetic rare‐earth cations and indicated the absence of localized moments on the Mo 16 clusters. The electronic structure of the LiLn 9 Mo 16 O 35 compounds was analyzed using molecular and periodic quantum calculations. The study of the molecular orbital diagrams of isolated Mo 16 O 36 models allowed the understanding of this unique metallic architecture. Periodic density functional theory calculations demonstrated that few interactions occur between the Mo 16 clusters, and predicted semiconducting properties for LiLn 9 Mo 16 O 35 as a band gap of 0.57 eV was computed for the lanthanum phase.