Uranyl–organic one- and two-dimensional assemblies with 2,2′-bipyridine-3,3′-dicarboxylic, biphenyl-3,3′,4,4′-tetracarboxylic and bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acids

Abstract

The complexes formed by uranyl ions with two aromatic and one alicyclic polycarboxylic acids have been crystallographically characterized. Three complexes were obtained under hydrothermal conditions with 2,2′-bipyridine-3,3′-dicarboxylic acid (H₂L¹), [UO₂(L¹)(H₂O)]·3H₂O (1), [UO₂(L¹)(DMF)]·0.5H₂O (2) and [UO₂(L¹)(H₂L¹)]·H₂O (3), all of which contain one-dimensional polymeric chains with the ligand being both chelating through one oxygen atom from each carboxylate group and bridging through the remaining donor atoms, the nitrogen atoms being uncoordinated. The last coordination site is occupied by either a water (1), a dimethylformamide (2), or a monodentate, zwitterionic H₂L¹ molecule (3). Biphenyl-3,3′,4,4′-tetracarboxylic acid (H₄L²) gives the complex [UO₂(H₂L²)(H₂O)₂]·2H₂O (4) under hydrothermal conditions, which is also a one-dimensional coordination polymer with uranyl chelation by only one carboxylate group from each aromatic ring. A two-dimensional assembly is finally obtained in the complex [(UO₂)₃(HL³)₂(H₂O)₆]·10H₂O (5), crystallized at room temperature, in which H₄L³ is the all-exo isomer of bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid. The three carboxylate groups in 5 are chelating, the ligand being thus a T-shaped node, and the layers are built from a tessellation of oblong twelve-membered rings arranged in herringbone fashion.