Structural trends and the electronic structure of the rare-earth oxomolybdates RMo5O8 (R = La, Ce, Pr, Nd, Sm, Eu and Gd) containing chains of bioctahedral Mo10 clusters

Abstract

The crystal structures of the rare-earth members of the series RMo5O8 (R = Ce to Eu) have been investigated and compared with those of the La and Gd members previously published in order to understand the influences of the size and the charge of the cation on the different Mo—Mo bonds. The RMo5O8 compounds crystallize in the monoclinic space group P21/c. Their crystal structure is characterized by bioctahedral Mo10 clusters forming extended chains. The results of our single-crystal studies show that the modification of charge predominantly affects the Mo—Mo bonds between the Mo10 clusters and, to a lesser extent, the intra-cluster distances, while the cationic size induces only small variations. Theoretical investigations confirm this statement and allow the understanding of the bonding mode in these compounds.