Uranyl–organic bilayer assemblies with flexible aromatic di-, tri- and tetracarboxylic acids

Complexes of Uranyl Ions with Aromatic Di‐ and Tetracarboxylates Involving [Ni(bipy)n]2+ (n = 2, 3) Counterions

“…The complex formed by hfdp 4– with uranyl ions alone crystallizes also as a thick 2D network, but in this case the uranyl cations are located on the faces and the ligands span the whole inner space, while the sheets in 4 can be seen as built of two thin layers connected to one another by the bridging bidentate carboxylate groups. It is notable that thick, bilayer arrangements were also found in uranyl ion complexes of the related ligand benzophenone‐3,3′,4,4′‐tetracarboxylate,, suggesting a particular propensity of these V‐shaped ligands to form such architectures. In this case also, parallel‐displaced π‐stacking interactions involving both ligands may be present, [centroid ··· centroid distances 3.836(5)–4.434(5) Å, dihedral angles 0–14.1(4)°], but examination of the HS shows that they are not greater than dispersion.…”

“…Concerning the syntheses, the most unexpected result here is that of complex 3 , prepared from 1,4,5,8‐naphthalenetetracarboxylic acid (H 4 ntc), but containing instead just its doubly deprotonated 1,8‐monoanhydride (ntcma 2– ). Anhydrides are commonly hydrolyzed under hydrothermal conditions,, but the six‐membered ring formed here enhances the stability of the anhydride unit. Another index of this stability is that recrystallization of H 4 ntc from dimethyl sulfoxide gives crystals of the monoanhydride .…”

“…No uranyl complex with either of the two naphthalene derivatives has been reported (but nine structures with the positional isomer 1,4‐naphthalenedicarboxylate are in the CSD, ). Uranyl complexation by 4,4′‐(1,1,1,3,3,3‐hexafluoroisopropylidene)diphthalic acid has been the subject of only one study, three complexes with the geometrically related benzophenone‐3,3′,4,4′‐tetracarboxylic acid having also been reported , …”

Design, synthesis and structure of uranyl coordination polymers from 2-D layer to 3-D network structure

“…The coordination environments of U2 and U3 are quite similar, except that the pair of terminal hydroxo groups on each U center (adjacent in the pentagonal plane) is different. The O9⋯O9 #1 separation on U2 is 2.69 Å, whereas the corresponding separation between terminal hydroxo groups on U3 [20]. The bond angles of O=U=O range from 178.0(6) to 179.6(6)°and the bond angles of O-U-O vary from 63.9(3) to 157.0(4)°.…”

“…X-ray single crystal analysis indicates that 2 is made up of one crystallographically independent UO 2 2þ , one hydroxo bridge, three terminal hydroxo ions, and two protonated NH 2 (CH 3 ) 2 + cations. [20]. The bond angle of O=U=O is 177.3 (7) Uranyl coordination polymers 517…”