Hydrothermal synthesis, crystal structure and properties of a two-dimensional uranyl coordination polymer based on a flexible zwitterionic ligand

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

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, cbtc^4- = cis,trans,cis-1,2,3,4-cyclobutanetetracarboxylate) is a discrete, dinuclear ring-shaped complex with a central cbtc^4- 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-pda^2- = 1,3-phenylenediacetate) is a daisy chain and [UO₂(pL1)(pdda)]₃·10H₂O (6, pdda^2- = 1,2-phenylenedioxydiacetate) is a double-stranded, ribbon-like chain. Both [UO₂(pL1)(pht)]·5H₂O (7, pht^2- = 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-chdc^2- = cis/trans-1,3-cyclohexanedicarboxylate) and [UO₂(pL1)(t-1,4-chdc)]·1.5H₂O (10, t-1,4-chdc^2- = 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-pda^2- = 1,2-phenylenediacetate) crystallize as diperiodic networks with hcb topology, and they display threefold parallel interpenetration. [HL2][(UO₂)₃(L2)(adc)₃]Br (13, adc^2- = 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, kpim^2- = 4-ketopimelate) is a three-periodic framework with pL1 molecules pillaring fes diperiodic subunits, whereas [(UO₂)₂(L2)₂(t-1,4-chdc)](NO₃)_1.7Br_0.3·6H₂O (15), the only cationic complex in the series, is a triperiodic framework with dmc topology and t-1,4-chdc^2- anions pillaring fes diperiodic subunits. Solid-state emission spectra and photoluminescence quantum yields are reported for all complexes.