A Highly Adjustable Coordination System: Nanotubular and Molecular Cage Species in Uranyl Ion Complexes with Kemp's Triacid

A unique example of topology tailoring in a uranyl-organic system is provided by the three-pronged Kemp's tricarboxylate ligand. While unexceptional one-dimensional polymers are formed with uranyl alone under solvo-hydrothermal conditions, addition of Ni2+ ions yields the nanotubular species [(UO2)(2)Ni(L)(2)(H2O)(4)](infinity), with a hydrophilic inner cavity lined by hydrated Ni2+ ions, and a hydrophobic outer surface. The further presence of 2,2'-bipyridine brings about the trapping of Ni2+ ions into counterions and formation of the octanuclear pseudocubic cage [(UO2)(8)(L)(6)(H2O)(6)](2-).