Ligand competition on uranyl ion: further examples of zwitterionic vs. anionic carboxylate coordination

Four uranyl ion mixed-ligand complexes involving anionic and zwitterionic carboxylate donors have been synthesized under solvo-hydrothermal conditions. [(UO2)(2)(pda)(2)(bet)(2)] (1), where pda(2-) is 1,3-phenylenediacetate and bet is betaine, crystallizes as a monoperiodic coordination polymer in which all ligands are kappa O-2,O '-chelated and UO2(pda)(bet)(2) units are decorating groups to the UO2(pda) chain. In [bcebpH(2)][UO2(bcebp)(H2O)(2)][UO2(tcenm)](4)<middle dot>2H(2)O (2), where tcenm(3-) is tris(2-carboxylatoethyl)nitromethane and bcebp is 4,4 '-bis(2-carboxylatoethyl)-4,4 '-bipyridinium, the two ligands are separated into different polymeric units, di- (hcb) and monoperiodic, respectively, and hydrogen bonding of the bcebpH(2)(2+) counterions to chains results in heteropolycatenation, with the counterions crossing four hexagonal networks. [(UO2)(2)(pht)(2)(bcpmb)] (3), where pht(2-) is phthalate and bcpmb is 1,4-bis(4 '-carbonylatopyridiniomethyl)benzene, is a diperiodic network with V2O5 topology, while [(UO2)(4)(O)(2)(kpim)(2)(bcpmb)] (4), where kpim(2-) is 4-ketopimelate, is a diperiodic network with bis(mu(3)-oxo)-bridged U4O2 secondary building units as nodes and sql topology. In this last case, the large size of the rings allows for 2D + 2D -> 3D inclined polycatenation to occur. The relative strength of anionic and zwitterionic carboxylate donors and the importance of weak interactions in the structures are discussed.