Hybrid Materials of the f-Elements Part II

The structural chemistry of crystalline hybrid materials bearing the uranyl cation, [UO2]2 +, is reviewed. A theme of uranyl hydrolysis and complex aqueous speciation as drivers for structural diversity is developed for materials constructed from coordinate covalent bonding with various O- and N-donor ligands. We begin with results from a number of exploratory hydrothermal synthesis efforts to highlight structural themes dominated by oligomeric secondary building units, and ligand affinities and sterics. The review then evolves to highlight more focused studies that endeavor to promote incorporation of targeted coordination geometries, compositions, and connectivities. Finally, we explore purely supramolecular systems that focus on the assembly of specific uranyl-bearing ions such as [UO2X4(H2O)n]2 − (X = Cl, Br) and [UO2(NCS)5 − n(H2O)n] (n = 0, 1) formed from high anion media. Assembly of these tectons is afforded through noncovalent interactions (synthons) with appropriate organic molecules to promote hydrogen or halogen bonding. The luminescent behavior of selected compounds is presented where clear structure–property relationships may be discerned.