Polyoxometalate molybdenum blue (MB) complexes typically exist as discrete multianionic clusters and are composed of repeating Mo building units. MB wheels such as {Mo 176 } and {Mo 154 } are made from pentagon-centered {Mo 8 } building blocks joined by equal number of {Mo 1 } units as loin, and {Mo 2 } dimer units as skirt along the ring edge, with the ring sizes of the MB wheels modulated by the {Mo 2 } units. Herein we report a new class of contracted lanthanide-doped MB structures that have replaced all the {Mo 2 } units with lanthanide ions on the inner rim, giving the general formula {Mo 90 Ln 10 }. We show three examples of this new decameric {Mo 90 Ln 10 } (Ln = La, Ce, and Pr) framework synthesized by high temperature reduction and demonstrate that later Ln ions result in {Mo 92 Ln 9 } (Ln = Nd, Sm), conserving one {Mo 2 } linker unit in its structure, as a consequence of the lanthanide contraction. Remarkably the {Mo 90 Ln 10 } compounds are the first examples of chargeneutral molybdate wheels as confirmed by BVS, solubility experiments, and redox titrations. We detail our full synthetic optimization for the isolation of these clusters and complete characterization by X-ray, TGA, UV-vis, and ICP studies. Finally, we show that this fine-tuned self-assembly process can be utilized to selectively enrich Ln-MB wheels for effective separation of lanthanides.

Peptide sequence can be used to control the self-assembly and structures of nanoscale molybdenum blue polyoxometalate (POM) wheel-shaped clusters.

The assembly of nanoscale polyoxometalate (POM) clusters has been dominated by the highly reduced icosahedral {Mo132} “browns” and the toroidal {Mo154} “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: [MoV52MoVI12H26O200]42− {Mo64} and [MoV40MoVI30H30O215]20− {Mo70}, 81 % and 57 % reduced, respectively. The {Mo64} cluster archetype has a super‐cube structure and is composed of five different types of building blocks, each arranged in overlayed Archimedean or Platonic polyhedra. The {Mo70} cluster comprises five tripodal {MoV6} and five tetrahedral {MoV2MoVI2} building blocks alternatively linked to form a loop with a pentagonal star topology. We also show how the reaction yielding the {Mo64} super‐cube can be used in the enrichment of lanthanides which exploit the differences in selectivity in the self‐assembly of the polyoxometalates.

The assembly of nanoscale polyoxometalate (POM) clusters has been dominated by the highly reduced icosahedral {Mo132} “browns” and the toroidal {Mo154} “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: [MoV52MoVI12H26O200]42− {Mo64} and [MoV40MoVI30H30O215]20− {Mo70}, 81 % and 57 % reduced, respectively. The {Mo64} cluster archetype has a super‐cube structure and is composed of five different types of building blocks, each arranged in overlayed Archimedean or Platonic polyhedra. The {Mo70} cluster comprises five tripodal {MoV6} and five tetrahedral {MoV2MoVI2} building blocks alternatively linked to form a loop with a pentagonal star topology. We also show how the reaction yielding the {Mo64} super‐cube can be used in the enrichment of lanthanides which exploit the differences in selectivity in the self‐assembly of the polyoxometalates.