title: Probing the influence of phosphonate bonding modes to uranium(VI) on structural topology and stability: a complementary experimental and computational investigation.
abstract: Systematic control of the reactions between U(VI) and 1,4-phenylenebis(methylene))bis(phosphonic acid) (pmbH4) allows for alterations in the bonding between these constituents and affords three uranyl phosphonate compounds with chiral one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) structures, namely, [TPA][UO2(pmbH3)(pmbH2)H2O]·2H2O (1), [NH4]2[UO2(pmb)] (2), UO2(pmbH2) (3), and the first uranyl mixed phosphite/phosphonate compound [TMA]2[(UO2)2(pmb)(HPO3)] (4) (TPA = NPr4+, TMA = NMe4+). These compounds crystallize in the space groups P212121, P1̅, P21/c, and Cmcm, respectively. Further investigation of the local uranyl coordination environment reveals that in 1 only oxygen atoms from P=O moieties ligate the uranium centers; whereas in 2 only P-O(-) oxygen atoms are involved in bonding and yield a layered topology. Compound 3 differs sharply from the first two in that conjugated P=O and P-O(-) oxygen atoms chelate the uranium centers resulting in a 3D framework. In compound 4, a phosphonate group bridges three uranyl centers further coordinated with a phosphite ligand HPO32–, which is a product of pmbH4 decomposing, forming a 2D layered structure. Compounds 3 and 4 also contain a different coordination environment for U(VI) than that found in 1 or 2. In this case, tetragonal bipyramidal UO6 units occur instead of the far more common UO7 pentagonal bipyramids found in 1 and 2. Interestingly, 1 converts to 3 at elevated reaction temperatures, indicating that the formation of 1 is likely under kinetic control. This is supported by thermal analysis, which reveals that 3 has higher thermal stability than 1 or 2. UV-vis-near-IR absorption and fluorescence spectroscopy show that the absorption and photoluminescence intensity increases from 1 to 4. Density functional theory electronic structure calculations provide insight into the nature of the interactions between U(VI) and the phosphonate ligands.
authors: Tao
authors: T
authors: Zheng
authors: §Key Laboratory of Nuclear Radiation and Nuclear Energy Technology and Key Laboratory For Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.
authors: Qun-Yan
authors: QY
authors: Wu
authors: Yang
authors: Y
authors: Gao
authors: Daxiang
authors: D
authors: Gui
authors: Shiwen
authors: S
authors: Qiu
authors: Lanhua
authors: L
authors: Chen
authors: Daopeng
authors: D
authors: Sheng
authors: Juan
authors: J
authors: Diwu
authors: §Key Laboratory of Nuclear Radiation and Nuclear Energy Technology and Key Laboratory For Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.
authors: Wei-Qun
authors: WQ
authors: Shi
authors: Zhifang
authors: Z
authors: Chai
authors: ∥Department of Chemistry and Biochemistry, Florida State University, 95 Chieftain Way, Tallahassee, Florida 32306, United States.
authors: Thomas E
authors: TE
authors: Albrecht-Schmitt
authors: Shuao
authors: S
authors: Wang
mesh_terms: D001665:Binding Sites; D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D063065:Organophosphonates / Q000737:chemistry*; D011789:Quantum Theory; D014501:Uranium / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D063065:Organophosphonates; D014501:Uranium