Lanthanides Singing the Blues: Their Fascinating Role in the Assembly of Gigantic Molybdenum Blue Wheels

Abstract

Molybdenum blues (MBs) are a distinct class of polyoxometalates, exhibiting versatile/impressive architectures and high structural flexibility. In acidified and reduced aqueous environments, isopolymolybdates generate precisely organizable building blocks, which enable unique nanoscopic molecular systems (MBs) to be constructed and further fine-tuned by hetero elements such as lanthanide (Ln) ions. This Review discusses wheel-shaped MB-based structure types with strong emphasis on the ∼30 Ln-containing MBs as of August 2021, which include both organically hybridized and nonhybridized structures synthesized to date. The spotlight is thereby put on the lanthanide ions and ligand types, which are crucial for the resulting Ln-patterns and alterations in the gigantic structures. Several critical steps and reaction conditions in their synthesis are highlighted, as well as appropriate methods to investigate them both in solid state and in solution. The final section addresses the homogeneous/ heterogeneous catalytic, molecular recognition and separation properties of wheel-shaped Ln-MBs, emphasizing their inimitable behavior and encouraging their application in these areas.

A New Molybdenum Blue Structure Type: How Uranium Expands this Family of Polyoxometalates

“…Lanthanides have been incorporated into molybdenum blue wheels but they simply replace molybdenum polyhedra instead of leading to a new connectivity. [10] Transition metals can lead to unprecedented structure types such as Mo 64 Ni 8 Ln 6 but many other variables such as degree of molybdenum reduction as well as the presence of lanthanides make it difficult to distinguish what causes the assembly of the new cluster in solution. [22] Adding the uranyl cation to a solution that would otherwise form Mo 154 instead causes the common MB building blocks to coordinate Mo 72 U 8 is chiral and crystallizes in the centrosymmetric space group P4/n as a racemic mixture.…”

“…[32] Inclusion of trivalent lanthanides into MB clusters reduces their symmetry owing to the high coordination numbers of the lanthanides. [10] As a result, clusters can become chiral but most often still crystallize as a racemic mixture. [33,34] Herein we report the synthesis of the first uraniumcontaining molybdenum blue clusters.…”

Solvent-modulated assembly of peptide and cerium functionalized gigantic {Mo120Ce6}2 dimers for high-efficiency photocatalytic oxidation

“…[32][33][34][35][36][37][38][39][40][41] By introducing lanthanides (Ln) as structural modulators and heterometal functionalities, the size, charge, nuclearity, curvature and even chirality can be controlled for the resulting clusters. [42][43][44][45][46][47][48][49][50][51][52][53][54] This indeed promoted the generation of a variety of MB clusters ranging from {Mo 90 Ce 10 } to {Mo 150 La 2 } as well as dimeric {Mo 128 Eu 4 } 2 and {Mo 100 Ce 6 } 2 . [43][44][45][46][47][48][49][50][51][52][53][54] Besides, amino acids and peptides have recently emerged as ligands to build functional MB clusters.…”

Trisubstituted 4f- and 4d tungstoantimonates as artificial phosphoesterases for nerve agent degradation

“…Polyoxometalates (POMs) 1 represent a broad class of anionic inorganic clusters with versatile structural topologies resulting in a variety of chemical and physical properties which can be modulated by molecular design. These features make them attractive materials in a wide range of fields like catalysis, 2 supramolecular chemistry, 3 magneto chemistry, 4 biological chemistry 5 including protein crystallography 6 and subject of challenging interdisciplinary research. 7 Their inherently high negative charge, water solubility and modular properties render POMs promising candidates for catalytic studies.…”