Restricted Speciation and Supramolecular Assembly in the 5f Block

Hybrid materials bearing elements from the 5f block display a rich diversity of coordination geometries, connectivities, and assembly motifs. Exemplary in this regard have been uranyl coordination polymers, which feature a wide range of secondary building units resulting from hydrolysis and oligomerization of the [UO2](2+) cation. An alternative approach to novel materials, however, suppresses hydrolysis and relies on non-covalent interactions (e.g. hydrogen or halogen bonding) to direct assembly of a more limited suite of species or building units. This may be achieved through the use of high-anion media to promote singular actinyl anions that are assembled with organic cations, or by way of functionalized chelating ligands that produce complexes suited for assembly through peripheral donor/acceptor sites. Presented in this Concept article is therefore an overview of our efforts in this arena. We highlight examples of each approach, share our thoughts regarding delineation of assembly criteria, and discuss the opportunities for exploring structure-property relationships in these systems.