Ligand competition on uranyl ion: further examples of zwitterionic vs anionic carboxylate coordination
Résumé
Four uranyl ion mixed-ligand complexes involving anionic and zwitterionic dicarboxylate donors have been synthesized under solvo-hydrothermal conditions. [(UO2)2(pda)2(bet)2] (1), where pda2– is 1,3-phenylenediacetate and bet is betaine, crystallizes as a monoperiodic coordination polymer in which all ligands are μ2O,O'-chelated and UO2(pda)(bet)2 units are decorating groups to the UO2(pda) chain. In [bcebpH2][UO2(bcebp)(H2O)2][UO2(tcenm)]4.2H2O (2), where tcenm3– is tris(2-carboxylatoethyl)nitromethane and bcebp is 4,4ʹ-bis(2-carboxylatoethyl)-4,4ʹ-bipyridinium, the two ligands are separated into different polymeric units, di- (hcb) and monoperiodic, respectively, and hydrogen bonding of the bcebpH22+ counterions to chains results in heteropolycatenation, with the counterions crossing four hexagonal networks. [(UO2)2(pht)2(bcpmb)] (3), where pht2– is phthalate and bcpmb is 1,4-bis(4ʹ-carbonylatopyridiniomethyl)benzene, is a diperiodic network with V2O5 topology, while [(UO2)4(O)2(kpim)2(bcpmb)] (4), where kpim is 4-ketopimelate, is a diperiodic network with bis(μ3-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 hydrogen bonding in the structures are discussed.
Domaines
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