Engineering Highly Reduced Molybdenum Polyoxometalates via the Incorporation of d and f Block Metal Ions

The assembly of nanoscale polyoxometalate (POM) clusters has been dominated by the highly reduced icosahedral {Mo-132} browns and the toroidal {Mo-154} blues which are 45 % and 18 % reduced, respectively. We hypothesised that there is space for a greater diversity of structures in this immediate reduction zone. Here we show it is possible to make highly reduced mix-valence POMs by presenting new classes of polyoxomolybdates: [(Mo52Mo12H26O200)-Mo-V-H-VI](4)(2-) {Mo-64} and [(Mo40Mo30H30O215)-Mo-V-H-VI](2)(0-) {Mo-70}, 81 % and 57 % reduced, respectively. The {Mo-64} cluster archetype has a supercube structure and is composed of five different types of building blocks, each arranged in overlayed Archimedean or Platonic polyhedra. The {Mo-70} cluster comprises five tripodal {Mo-6(V)} and five tetrahedral {(Mo2Mo2VI)-Mo-V} building blocks alternatively linked to form a loop with a pentagonal star topology. We also show how the reaction yielding the {Mo-64} super-cube can be used in the enrichment of lanthanides which exploit the differences in selectivity in the self-assembly of the polyoxometalates.

Automated summary

The study demonstrates the possibility of greater structural diversity in the assembly of nanoscale POM clusters, presenting new classes of highly reduced mixed-valence POMs. This includes the supercube structure of {Mo-64} and the pentagonal star topology of {Mo-70}, with potential applications in lanthanide enrichment through differences in selectivity in the self-assembly of polyoxometalates.