Ag I and Pb II as Additional Assembling Cations in Uranyl Coordination Polymers and Frameworks

Pierre Thuéry (1) , Jack Harrowfield (2)

1 LCMCE - Laboratoire de Chimie Moléculaire et de Catalyse pour l'Energie (ex LCCEF)
2 ISIS - Institut de Science et d'ingénierie supramoléculaires

Five mono-or polycarboxylic acids have been used to generate a series of eight heterometallic uranyl complexes involving silver(I) or lead(II) cations, all synthesized under (solvo)-hydrothermal conditions. Pimelic acid (H2pim) gave complexes [Ag(bipy)2]2[UO2(pim)(NO3)]2 (1) and [UO2Pb(pim)2(bipy)(H2O)]0.5bipyH2O (2) (bipy = 2,2ʹ-bipyridine), which both crystallize as one-dimensional (1D) polymers, but differ in that the silver(I) cations are separate counter-ions, while carboxylate-bound lead(II) cations are an essential component of the polymer. Only silver(I)-containing species were obtained with all-cis 1,3,5-cyclohexanetricarboxylic acid (H3chtc), [UO2Ag(chtc)(H2O)2] (3) and [Ag(bipy)(CH3CN)]2[UO2(chtc)]2 (4); both contain two-dimensional (2D) uranyl carboxylate subunits with honeycomb {6 3 } topology, these being united into a three-dimensional (3D) framework with the lonsdaleite {6 6 } topology by bridging, oxo-bound silver(I) cations in 3. Both silver-and lead-containing complexes were obtained with 3,3ʹ,4,4ʹ-biphenyltetracarboxylic acid (H4bptc), [UO2Ag(bptc)(4,4ʹ-bipyH)] (5) and [UO2Pb(bptc)(bipy)2] (6) (4,4ʹ-bipy = 4,4ʹ-bipyridine), and they both display a 2D uranyl carboxylate network with the {4 4 .6 2 } topology, the additional cations and N-donors being decorating species. In this case, a higher dimensionality was obtained not with an additional cation, but with a coordinated N-methyl-2-pyrrolidone (NMP) molecule, since [(UO2)2(bptc)(NMP)1.5(H2O)1.5]1.5H2O (7) crystallizes as a three-dimensional (3D) framework. In the presence of silver(I), 3-pyrimidin-2-yl-benzoic acid (Hpyb) gave the complex [UO2Ag(pyb)3(H2O)2]4H2O (8), in which the two coordination sites are occupied in accord with Hard/Soft Acid/Base (HSAB) principles, uranyl being chelated by three carboxylate groups and silver(I) being bound to nitrogen atoms; the 1D polymer formed bridges to another through silver–uranyl oxo bonding. In contrast, the homometallic, molecular complex [UO2(pyb)2(bipy)] (9) was obtained in the presence of lead(II) cations. The lead-containing complex with 2,6-pyridinedicarboxylic acid (H2pydc), [UO2Pb2(pydc)2(phen)2(HCOO)1.5(NO3)0.5]0.5H2O (10) (phen = 1,10-phenanthroline), crystallizes as a 1D polymer in which uranyl is bound to two O,N,O-donors, as usual with this ligand, polymerization being due to lateral double lead(II) bridges. Variations in uranyl emission maxima positions appear to be essentially related to the uranium coordination number within the present series.

Domaines: Matériaux

Pierre Thuéry, Jack Harrowfield. Ag I and Pb II as Additional Assembling Cations in Uranyl Coordination Polymers and Frameworks. Crystal Growth & Design, 2017, ⟨10.1021/acs.cgd.7b00081⟩. ⟨cea-01484247⟩