Zwitterionic and Anionic Polycarboxylates as Coligands in Uranyl Ion Complexes, and Their Influence on Periodicity and Topology

Abstract

The three zwitterionic di- and tricarboxylate ligands 1,1′-[(2,3,5,6-tetramethylbenzene-1,4-diyl)­bis­(methylene)]­bis­(pyridin-1-ium-4-carboxylate) (pL1), 1,1′-[(2,3,5,6-tetramethylbenzene-1,4-diyl)­bis­(methylene)]­bis­(pyridin-1-ium-3-carboxylate) (mL1), and 1,1′,1″-[(2,4,6-trimethylbenzene-1,3,5-triyl)­tris­(methylene)]­tris­(pyridin-1-ium-4-carboxylate) (L2) have been used as ligands to synthesize a series of 15 uranyl ion complexes involving various anionic coligands, in most cases polycarboxylates. [(UO2)2(pL1)2(cbtc)­(H2O)2]·10H2O (1, cbtc4– = cis,trans,cis-1,2,3,4-cyclobutanetetracarboxylate) is a discrete, dinuclear ring-shaped complex with a central cbtc4– pillar. While [UO2(pL1)­(NO3)2] (2), [UO2(pL1)­(OAc)2] (3), and [UO2(pL1)­(HCOO)2] (4) are simple chains, [(UO2)2(mL1)­(1,3-pda)2] (5, 1,3-pda2– = 1,3-phenylenediacetate) is a daisy chain and [UO2(pL1)­(pdda)]3·10H2O (6, pdda2– = 1,2-phenylenedioxydiacetate) is a double-stranded, ribbon-like chain. Both [UO2(pL1)­(pht)]·5H2O (7, pht2– = phthalate) and [(UO2)3(mL1)­(pht)2(OH)2] (8) crystallize as diperiodic networks with the sql topology, the latter involving hydroxo-bridged trinuclear nodes. [(UO2)2(pL1)­(c/t-1,3-chdc)2] (9, c/t-1,3-chdc2– = cis/trans-1,3-cyclohexanedicarboxylate) and [UO2(pL1)­(t-1,4-chdc)]·1.5H2O (10, t-1,4-chdc2– = trans-1,4-cyclohexanedicarboxylate) are also diperiodic, with the V2O5 and sql topologies, respectively. Both [(UO2)2(mL1)­(c/t-1,4-chdc)2] (11) and [(UO2)2(pL1)­(1,2-pda)2] (12, 1,2-pda2– = 1,2-phenylenediacetate) crystallize as diperiodic networks with hcb topology, and they display threefold parallel interpenetration. [HL2]­[(UO2)3(L2)­(adc)3]Br (13, adc2– = 1,3-adamantanedicarboxylate) contains a very corrugated hcb network with two different kinds of cells, and the uncoordinated HL2+ molecule associates with the coordinated L2 to form a capsule containing the bromide anion. [(UO2)2(pL1)­(kpim)2] (14, kpim2– = 4-ketopimelate) is a three-periodic framework with pL1 molecules pillaring fes diperiodic subunits, whereas [(UO2)2(L2)2(t-1,4-chdc)]­(NO3)1.7Br0.3·6H2O (15), the only cationic complex in the series, is a triperiodic framework with dmc topology and t-1,4-chdc2– anions pillaring fes diperiodic subunits. Solid-state emission spectra and photoluminescence quantum yields are reported for all complexes.

Varied role of organic carboxylate dizwitterions and anionic donors in mixed-ligand uranyl ion coordination polymers

“…There is no evidence that the p L interactions with U VI are particularly affected by those with 3-SB 2− , its simple bis(κ 1 O)-bridging role found here and in 1 being common for this ligand. 6 All three sulfonate oxygen atoms act as hydrogen bond acceptors from four uncoordinated water molecules, these being also bound to one another, but not to carboxylate groups (Table 2). These water molecules are part of chains which in effect convert the monoperiodic coordination polymer units into a triperiodic assembly.…”

“…Both p LH 2 Cl 2 and m LH 2 Cl 2 were prepared according to previous literature. 6,7 Elemental analyses were performed by MEDAC Ltd. For all syntheses, the mixtures in demineralized water and dimethylacetamide (DMA) were placed in 10 mL tightly closed glass vessels and heated at 140 °C in a sand bath, under autogenous pressure.…”

“…(1,3-phenylenediacetate or cis/trans-1,4cyclohexanedicarboxylate) are κ 2 O,O′-chelating an hexagonalbipyramidal U VI cation, 6 with bond lengths in the ranges of 2.489(3)-2.5317(15) and 2.405(9)-2.4915(15) Å, respectively; these U-O bonds to mL appear to be slightly longer than those to anionic carboxylates but the difference is small, so there is no certain evidence of an overwhelming influence of differences in donor capacity between zwitterionic and anionic carboxylates. Other factors such as hydrogen bonding may well explain the structural variations.…”

“…The products obtained in the present work rather nicely illustrate the variable nature of solvothermal syntheses of uranyl ion coordination polymers. Together with those in the cases previously reported, 6 the anionic ligands used here are the only ones for which crystalline materials could be isolated among the many which were tried, many anionic polycarboxylates, albeit closely related to those in the compounds described, giving no crystals suitable for structure determination. In only one case, complex 1, does the stoichiometry of the isolated material match that of the reaction mixture and while the composition of all solids shows a mixture of ligands to be present, in one case, complex 4, one of the deliberately added coligands is not present, and in another, complex 5, the two ligands are separated into two distinct polymeric species.…”

“…Further work, however, has shown this not to be an infallible procedure. Following previous work 6 with the organic dizwitterions 1,1′- [(2,3,5,6-tetramethylbenzene-1,4diyl)bis(methylene)]bis(pyridin-1-ium-4-carboxylate) (pL) and 1,1′- [(2,3,5,6-tetramethylbenzene-1,4-diyl)bis(methylene)] bis(pyridin-1-ium-3-carboxylate) (mL), shown in Scheme 1, we present herein the synthesis, crystal structure and luminescence properties in the solid state of five complexes involving one or the other of these ligands in association with anionic donors in the form of partially protonated pyromellitate (H 2 PM 2− ), 3-sulfobenzoate (3-SB 2− ), 2-sulfobenzoate (2-SB 2− ), 2,5-thiophenedicarboxylate (TDC 2− ), or a mixture of oxo and hydroxo anions. The crystal structures of the mono-and diperiodic assemblies formed are interpreted in terms of reasons for their novelty.…”