Uranyl Diphosphonates Research Articles

Construction of uranyl phosphonates from multifunctional zwitterionic ligands

Abstract Two new uranyl diphosphonates, namely, [UO2(H3L1)2(H2O)]·4H2O (1) and [UO2(H3L2)(H2O)]·3H2O (2), H4L1 = PyNHCH(PO3H2)2, H5L2 = Py(COOH)NHCH(PO3H2)2, have been hydrothermally synthesized from the reactions of two diphosphonate ligands with uranyl nitrate hexahydrate and characterized systematically using powder and single-crystal X-ray diffraction, IR, EA, TGA and fluorescent emission measurements. The proton transfer from the phosphonic acid groups to the pyridine and imine groups leads to the formation of zwitterionic ligands. The diphosphonate ligand in compound 1 adopts chelate coordination mode resulting in molecular structure while displays chelate-bridging coordination mode in compound 2 leading to the formation of 1D infinite chain structure. The fluorescent properties of compounds 1 and 2 were also investigated.

Construction of Uranyl Organic Hybrids by Phosphonate and in Situ Generated Carboxyphosphonate Ligands.

The hydrothermal reaction of uranyl ions with (5-methyl-1,3-phenylene)diphosphonic acid (H4MPDP) in the presence of additives such as nitric acid, N-bearing species, and heterometal ions yielded five new uranyl organic hybrids: (H3O)[(UO2)5(H2O)4(H3DPB)2(H2DPB)(HDPB)]·2H2O (1), (Hphen)(phen)[(UO2)3(H2DPB)(HDPB)] (2), (H2dipy)[(UO2)3(MPDP)2] (3), Zn(bipy)(UO2)(MPDP) (4), and Co(bipy)(UO2)(MPDP)·H2O (5) (H5DPB = 3,5-diphosphonobenzoic acid; phen = 1,10-phenanthroline; dipy = 4,4'-bipyridine; bipy = 2,2'-bipyridine). Single-crystal X-ray diffraction (XRD) demonstrates that 1 and 2 are 3D frameworks constructed of uranyl centers and carboxyphosphonate DPB ligands; the latter were formed via the in situ oxidation of H4MPDP. In the homometallic uranyl diphosphonate 3, less common UO6 square bipyramids connected by MPDP ligands were incorporated to form the 2D assembly. A further introduction of heterometal ions produced two heterobimetallic uranyl phosphonates 4 and 5. Both of them show layered structures, formed by UO6 square bipyramids linked by MPDP ligands with heterometal-centered polyhedra decorated on the sides of the layers. It is found that the pH and heterometal ions have significant effects on the structures of the complexes. In addition to the syntheses and XRD characterization, the spectroscopic properties of these uranyl complexes were also addressed. To complement the experimental results, density functional theory calculations were carried out on several model complexes that feature a homo- or heterobimetallic molecular skeleton. Geometrical/electronic structures, IR spectra, and electronic absorptions were discussed.

Incorporation of Cu2+ Ions into Nanotubular Uranyl Diphosphonates

Three new multidimensional polymetallic uranyl diphosphonates were crystallized under mild hydrothermal conditions: [Cu(H2O)]2{(UO2)4F2[(PO3C6H4)(C6H4PO3H)3]2(bipym)}·6H2O (1), [Cu(H2O)]2{(UO2)4[(C6H4PO3)(C6H4PO3H)]4(bipym)} (2), and Cu{(UO2)(C6H4PO3)2(bipym)}·H2O (3). Compound 1 consists of UO6F pentagonal bipyramids connected by diphosphonate moieties into a tubular channel. The Cu(2+) cations are stabilized between the nanotubular subunits by 2,2'-bipyrimidine (bipym). The structure of 2 is similar to 1, except that it consists of relatively rare UO6 tetragonal bipyramids bridged by diphosphonate groups. Compound 3 also contains UO6 tetragonal bipyramids. Unlike compounds 1 and 2, only two of the tetradentate N atoms of the binucleating bipym group are coordinated. All three compounds show luminescent properties under ambient conditions, with evidence of the characteristic vibronically coupled charge-transfer based uranyl cation emissions.

Structural Variation within Heterometallic Uranyl Hybrids Based on Flexible Alkyldiphosphonate Ligands

Five novel zinc uranyl diphosphonates have been hydrothermally synthesized by using a series of flexible diphosphonate ligands, including ethane-1,2-diyldiphosphonic acid (H4EDP), propane-1,3-diyldiphosphonic acid (H4PDP), and butane-1,4-diyldiphosphonic acid (H4BDP). Compound Zn(H2tib)(UO2)2(EDP)(HEDP)(H2EDP)0.5·3H2O (EDP-ZnU1, tib = 1,3,5-tri(1H-imidazol-1-yl)benzene) comprises dimeric U2O12 unit condensed by two UO7 pentagonal bipyramids, which are further connected by Zn-centered polyhedra and EDP ligands resulting in a 3-dimensional framework. Compound [Zn(bipy)(H2O)](UO2)(PDP) (PDP-ZnU1, bipy = 2,2′-bipyridine) also features U2O12 dimers and Zn-centered polyhedra, but a layered arrangement is formed. Different from that in PDP-ZnU1, the uranium exists in the form of UO6 tetragonal bipyramid and is surrounded by four PDP ligands to generate the layered structure of Zn(bipy)(UO2)(PDP) (PDP-ZnU2). ZnO2N2 tetrahedra are connected on both sides of the layers. Both Zn2(phen)4(UO2)3(BDP)(HBDP)2·4H2O (BDP-ZnU1, phen = 1,10-phenanthroline) and Zn2(bipy)2(UO2)3(HBDP)2(H2BDP)2 (BDP-ZnU2) contain U2O12 dimers and UO6 tetragonal bipyramids. In BDP-ZnU1, uranyl centers are bridged by BDP to form a 2-dimensional structure, on which Zn(phen)2 are decorated. Whereas in BDP-ZnU2, uranyl phosphonate layers are connected by bridging ZnO3N2 to produce framework structure. All of these compounds have been investigated by IR and photoluminescent spectroscopy. Their characteristic green light emissions have been attributed to transition properties of uranyl dications.

Three New Silver Uranyl Diphosphonates: Structures and Properties

The hydrothermal reaction of uranium trioxide and methylenediphosphonic acid in the presence of silver nitrate resulted in the formation of three new uranyl coordination polymers: AgUO2[CH2(PO3)(PO3H)] (Ag-1), [Ag2(H2O)1.5]{(UO2)2[CH2(PO3)2]F2}·(H2O)0.5 (Ag-2), and Ag2UO2[CH2(PO3)2] (Ag-3). All consist of uranyl pentagonal bipyramids that form two-dimensional layered structures. Ag-1 and Ag-3 possess the same structural building unit, but the structures are different; Ag-3 is formed through edge-sharing of F atoms to form UO5F2 dimers. The pH and silver cation have significant effects on the structure that is synthesized. Raman spectra of single crystals of Ag-1, Ag-2, and Ag-3 reveal v1 UO2(2+) symmetric stretches of 816 and 829, 822, and 802 cm(-1), respectively. Electronic structure calculations were performed using the projector augmented wave (PAW) method with density functional theory (DFT) to gain insight into the nature of bonding and electronic characteristics of the synthesized compounds. Herein, we report the syntheses, crystal structures, Raman spectroscopy, and luminescent behavior of these three compounds.

Flexible Diphosphonic Acids for the Isolation of Uranyl Hybrids with Heterometallic UVI═O—ZnII Cation–Cation Interactions

A family of uranyl diphosphonates have been hydrothermally synthesized using various flexible diphosphonic acids and Zn(UO2)(OAc)4·7H2O in the presence of bipy or phen. Single-crystal X-ray analyses indicate that these compounds represent the first examples of uranyl phosphonates with heterometallic U(VI)═O-Zn(II) cation-cation interactions.

From 1D Chain to 3D Framework Uranyl Diphosphonates: Syntheses, Crystal Structures, and Selective Ion Exchange

In this work, we demonstrate a family of new inorganic-organic hybrid uranyl diphosphonates based on 1-hydroxyethylidenediphosphonic acid (H(4)L) linker by using hydrothermal method. These compounds, (Hbpi)[(UO(2))(H(2)O)(HL)]·H(2)O (UP-1), represents 1D structure, (Hbpi)[(UO(2))(H(2)O)(HL)] (UP-2), (H(2)dib)(0.5)[(UO(2))(H(2)O)(HL)] (UP-3), and [(UO(2))(H(2)O)(H(2)L)]·2H(2)O (UP-4) feature 2D architectures, (H(2)bipy){[(UO(2))(H(2)O)](2)[(UO(2))(H(2)O)(2)](L)(2)}·2H(2)O (UP-5), and (H(3)O)(2){[(UO(2))(H(2)O)](3)(L)(2)}·2H(2)O (UP-6) adopt 3D networks (bpi: 1-(biphenyl-4-yl)-1H-imidazole, dib: 1,4-di(1H-imidazol-1-yl)benzene, bipy: 2,2'-bipyridine). Among them, UP-1, UP-2, UP-3, and UP-4 possess the same structural building unit but with different structures. UP-5 and UP-6 feature the same UO(2)/L ratio of 3:2 but a different structural building unit. Photoluminescence studies reveal that UP-5 displays characteristic emissions of uranyl cations. Ion-exchange experiments demonstrate that the H(3)O(+) in UP-6 can be easily and selectively exchanged by monovalent cations including Na(+), K(+), Cs(+), and Ag(+) cations, whereas the framework retains identical as confirmed by single-crystal X-ray diffractions.

Tailor-Made Zinc Uranyl Diphosphonates from Layered to Framework Structures

Hydrothermal reactions of zinc uranyl acetate and 1-hydroxyethylidenediphosphonic acid (H4L) with 1,10-phenanthroline (phen), 2,2′-bipyridine (bipy), 1H-benzo[d]imidazole (bi), or 1-phenyl-1H-imidazole (pi) resulted in the formation of four new zinc uranyl compounds, namely, [Zn2(phen)2(UO2)2(L)2(H2O)3]·3H2O (ZnUP-1), Zn2(bipy)2(UO2)2(L)2(H2O)2 (ZnUP-2), (Hbi)[Zn0.5(UO2)2(L)(H2L)(H2O)3]·3H2O (ZnUP-3), and (Hpi)[Zn(UO2)2(H2O)4(L)(HL)]·H2O (ZnUP-4). These four structures all comprise uranyl diphosphonate layers formed by UO7 pentagonal bipyramids and PO3C tetrahedra. Such layers are further connected by Zn-centered polyhedra by sharing oxygens from phosphonate groups. For ZnUP-1 and ZnUP-2, the zinc atoms are terminally coordinated by phen and bipy molecules, respectively, resulting in two-dimensional (2-D) hybrid materials. In ZnUP-3 and ZnUP-4, the uranyl phosphonate layers are joined together by Zn–O polyhedra forming three-dimensional (3-D) frameworks. The structures of ZnUP-3 and ZnUP-4 contain large channels along the a-axis with apertures around 3.4 × 13.3 and 4.4 × 12.2 Å2, respectively. Protonated templates exist in the channels, filling the space and compensating the negative charge of the anionic frameworks. Photoluminescent studies reveal that ZnUP-1 and ZnUP-2 exhibit the characteristic vibronically coupled charge-transfer based UO22+ emission.

Metal-Controlled Assembly of Uranyl Diphosphonates toward the Design of Functional Uranyl Nanotubules

Two uranyl nanotubules with elliptical cross sections were synthesized in high yield from complex and large oxoanions using hydrothermal reactions of uranyl salts with 1,4-benzenebisphosphonic acid or 4,4'-biphenylenbisphosphonic acid and Cs(+) or Rb(+) cations in the presence of hydrofluoric acid. Disordered Cs(+)/Rb(+) cations and solvent molecules are present within and/or between the nanotubules. Ion-exchange experiments with A(2){(UO(2))(2)F(PO(3)HC(6)H(4)C(6)H(4)PO(3)H)(PO(3)HC(6)H(4)C(6)H(4)PO(3))}·2H(2)O (A = Cs(+), Rb(+)), revealed that A(+) cations can be exchanged for Ag(+) ions. The uranyl phenyldiphosphonate nanotubules, Cs(3.62)H(0.38)[(UO(2))(4){C(6)H(4)(PO(2)OH)(2)}(3){C(6)H(4)(PO(3))(2)}F(2)]·nH(2)O, show high stability and exceptional ion-exchange properties toward monovalent cations, as demonstrated by ion-exchange studies with selected cations, Na(+), K(+), Tl(+), and Ag(+). Studies on ion-exchanged single crystal using scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM/EDS) provide evidence for chemical zonation in Cs(3.62)H(0.38)[(UO(2))(4){C(6)H(4)(PO(2)OH)(2)}(3){C(6)H(4)(PO(3))(2)}F(2)]·nH(2)O, as might be expected for exchange through a diffusion mechanism.

Syntheses of Uranyl Diphosphonate Compounds Using Encapsulated Cations as Structure Directing Agents

Five new uranyl phenyldiphosphonate compounds have been synthesized using cations encapsulated by a variety of crown ethers (18-crown-6, 15-crown-5, and 12-crown-4) as structure directing agents under mild hydrothermal conditions. These compounds, [(H3O)@C12H24O6]{(UO2)2[C6H4(PO3H)2]2F}·2H2O (U18C6-1), [K@C12H24O6]{(UO2)2[C6H4(PO3H)2]2F}·4H2O (U18C6-2), [(H3O)@C10H20O5]{(UO2)2[C6H4(PO3H)2]2F}·4H2O (U15C5-1), and [(H3O)C8H16O4][(UO2)(PO3HC6H4PO3H0.5)]2 (U12C4-1) are all layered, while [(H3O)C8H16O4]{(UO2)3[(PO3HC6H4PO3H0.5)2C6H4(PO3H)2]} (U12C4-2) adopts a three-dimensional channel structure. U18C6-1, U18C6-2, and U15C5-1 are constructed from UO6F pentagonal bipyramids, whereas U12C4-1 and U12C4-2 have UO7 and UO6 units, respectively. The crystal structures corroborate the proposed C3v and D3d conformational symmetries observed in H3O+ and K+ crown ether inclusion complexes, respectively. These compounds fluoresce at room temperature and display a red shift of 35 nm compared to the luminescence spectrum of...

Pillared and open-framework uranyl diphosphonates

The hydrothermal reactions of uranium trioxide, uranyl acetate, or uranyl nitrate with 1,4-benzenebisphosphonic acid in the presence of very small amount of HF at 200 °C results in the formation of three different uranyl diphosphonate compounds, [H 3O] 2{(UO 2) 6[C 6H 4(PO 3)(PO 2OH)] 2[C 6H 4(PO 2OH) 2] 2[C 6H 4(PO 3) 2]}(H 2O) 2 ( Ubbp-1), [H 3O] 4{(UO 2) 4[C 6H 4(PO 3) 2] 2F 4}·H 2O ( Ubbp-2), and {(UO 2)[C 6H 2F 2(PO 2OH) 2(H 2O)} 2·H 2O ( Ubbp-3). The crystal structures of these compounds were determined by single crystal X-ray diffraction experiments. Ubbp-1 consists of UO 7 pentagonal bipyramids that are bridged by the phosphonate moieties to form a three-dimensional pillared structure. Ubbp-2 is composed of UO 5F 2 pentagonal bipyramids that are bridged through the phosphonate oxygen atoms into one-dimensional chains that are cross-linked by the phenyl spacers into a pillared structure. The structure of Ubbp-3 is a three-dimensional open-framework with large channels containing water molecules with internal dimensions of approximately 10.9×10.9 Å. Ubbp-1 and Ubbp-2 fluoresce at room temperature.

Hydrothermal Synthesis and Structural Characterization of Organically Templated Uranyl Diphosphonate Compounds

The hydrothermal treatment of uranyl nitrate and 1,4-benzenebisphosphonic acid with a variety of aliphatic amines (tetramethylammonium hydroxide, tetraethylammonium hydroxide, and diethyldimethylammonium hydroxide) and small quantities of hydrofluoric acid at 200 °C results in the crystallization of a series of layered uranyl diphosphonate compounds, [(CH3)4N][(UO2)3(O3PC6H4PO3H)2F(H2O)]·0.5H2O (Me4Ubbp), [(CH3CH2)4N]{(UO2)[C6H4(PO3H)(PO3H1.5)]2(H2O)} (Et4Ubbp), and [(CH3CH2)2N(CH3)2][(UO2)3(O3PC6H4PO3H)2F(H2O)] (Et2Me2Ubbp). All these new compounds have layered structures, but the structures of Me4Ubbp and Et2Me2Ubbp are similar in that they both contain UO6F and UO7 pentagonal bipyramids within dimers that are bridged by the phosphonate into a three-dimensional structure. The structure of Et4Ubbp contains a single crystallographically unique UO7 unit. The edge-sharing pentagonal bipyramids are linked into chains formulated as {(UO2)[C6H4(PO3H)(PO3H1.5)]2(H2O)}1−. The voids in these structures are filled...

Differential Ion Exchange in Elliptical Uranyl Diphosphonate Nanotubules

A simple route to a uranyl diphosphonate with an elliptical nanotubular structure has been developed. The interior of the nanotubules provides a different chemical environment than the exterior with regards to the exchange of Cs{sup +} cations for Ag{sup +} cations, thus demonstrating that uranyl nanotubules are functional materials.

Differential Ion Exchange in Elliptical Uranyl Diphosphonate Nanotubules

Eine einfache Route zu einem Uranyldiphosphonat mit der Struktur einer elliptischen Nanoröhre wurde entwickelt (siehe Bild; C schwarz, O rot, Cs blau, F gelb, pentagonal-bipyramidales UO7 grün, Phosphonat-Tetraeder violett). Die Nanoröhren bieten Cs+-Ionen im Inneren eine andere chemische Umgebung als solchen an der Außenseite, wie anhand des Austauschs von Cs+ gegen Ag+ gezeigt wurde.

Unusual case of a polar copper(II) uranyl phosphonate that fluoresces

Abstract A polar Cu(II) uranyl diphosphonate, Cu(H2O)4(UO2)3(H2O)2[CH2(PO3)2]2·5H2O, has been prepared under mild hydrothermal conditions. This compound has direct linkages between the oxo atoms of the uranyl moieties and the Cu(II) centers. Despite the presence of Cu(II) in the structure, vibronically-coupled emission is still observed, most likely because there are two crystallographically unique uranyl moieties, only one of which bonds to Cu(II).

Uranyl Diphosphonates with Pillared Structures

A series of five uranyl diphosphonates with pillared and canted pillared structures have been prepared and characterized. These compounds are constructed from UO(6) tetragonal bipyramids and UO(7) pentagonal bipyramids that are bridged by the diphosphonate anions. All of these compounds fluoresce at room temperature.