3D Uranyl Organic Frameworks Supported by Rigid Octadentate Carboxylate Ligand: Synthesis, Structure Diversity, and Luminescence Properties.

Seven three dimensional (3D) uranyl organic frameworks (UOFs), formulated as [NH ][(UO ) (HTTDS)(H O)] (1), [(UO ) (HTTDS) ](HIM) (2, IM=imidazole), [(UO ) (TTDS)(H O) (Phen) ] (3, Phen=1,10-phenanthroline), [Zn(H O) ] [(UO ) (HTTDS)(H O) ] (4), and {(UO ) [Zn(H O) ] (TTDS)} (5), {Zn(UO ) (H O)(Dib) (HDib)(HTTDS)} (6, Dib=1,4-di(1H-imidazol-1-yl)benzene) and [Na]{(UO ) [Cu (u -OH)(H O) ](TTDS) } (7) have been hydrothermally prepared using a rigid octadentate carboxylate ligand, tetrakis(3,5-dicarboxyphenyl)silicon(H TTDS). These UOFs have different 3D self-assembled structures as a function of co-ligands, structure-directing agents and transition metals. The structure of 1 has an infinite ribbon formed by the UO pentagonal bipyramid bridged by carboxylate groups. With further introduction of auxiliary N-donor ligands, different structure of 2 and 3 are formed, in 2 the imidazole serves as space filler, while in 3 the Phen are bound to [UO ] units as co-ligands. The second metal centers were introduced in the syntheses of 4-7, and in all cases, they are part of the final structures, either as a counterion (4) or as a component of framework (5-7). Interesting, in 7, a rare polyoxometalate [Cu (μ -OH)O (O CR) ] cluster was found in the structure. It acts as an inorganic building unit together with the dimer [(UO ) (O CR) ] unit. Those uranyl carboxylates were sufficiently determined by single crystal X-ray diffraction, and their topological structures and luminescence properties were analyzed in detail.