Lord of the Rings: An Octameric Lanthanum Pyrazolonate Cluster

High‐Relaxivity MRI Contrast Agents: Where Coordination Chemistry Meets Medical Imaging

“…The dominant example is the "Lord of the Rings" (31). [89] The La 8 L 8 complex forms, however, instead of the analogous tetrahedron In 6 L 6 ( Figure 11). Eight lanthanum atoms occupy the eight vertices of the polyhedron, while each ligand occupies one of the eight triangular faces.…”

Metallo-supramolecular capsules

“…In the broad topic of this section, transition metals are often used for templating, and significant advances in large superstructures or clusters have been made by Fujita and coworkers [12][13][14][15][16][17][18], Stang and co-workers [19,20], Raymond and co-workers [21][22][23][24][25][26][27] and Ward and co-workers [28][29][30][31][32][33][34][35][36]. Fujita has reacted pyridyl or pyrimidyl functionalised planar or near planar ligands (that are typically triangular) with cis-protected palladium in order to synthesise a substantial series of metalorganic cages [12][13][14][15][16][17][18].…”

“…When an anthracene spacer is used, either triple helicate and tetrahedral cluster interconversion is observed, a phenomenon which is also controlled by host-guest interactions, also with tetraalkylammonium guest species [24]. In moving from transition to lanthanide metals, Raymond and co-workers also reported an octameric lanthanum pyrazolate cluster [25]. This self-assembly is more difficult to control given the high coordination numbers of the lanthanides, but the authors successfully react a rigid tris-bidentate 4-acyl-2-pyrazolin-5-one ligand with lanthanum acetylacetonate in DMSO to afford a single selfassembled 'ring-like' metal-organic cluster that is ∼3 nm in diameter.…”

Metal-Controlled Diastereoselective Self-Assembly and Circularly Polarized Luminescence of a Chiral Heptanuclear Europium Wheel

“…1, 2 In particular the circularly polarized luminescence (CPL) observed in chiral lanthanide complexes is of high current interest in biological probing and display technologies 1, 3-6 due to the attractive properties of lanthanide ions (large Stokes shift, long lifetimes, narrow emission bands, high quantum yields). 7 However, enantiopure lanthanide complexes are mostly limited to few examples of mononuclear compounds 1, 83, 94, 5, 10, 11 and dinuclear helicates 12-14 Although the supramolecular chemistry of lanthanide ions is less developed with respect to d-block metal ions, reports of lanthanide based polynuclear assemblies 15-20 which have pre-programmed new original structures 21-23 and of nanosized complexes that show fascinating optical, 24 and magnetic properties 25 are rapidly increasing. However, the high kinetic lability and lack of stereochemical preferences of lanthanide ions renders very difficult the control of their coordination sphere.…”