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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.

The hydrothermal treatment of uranium trioxide and methylenediphosphonic acid with a variety of amines (2,2-dipyridyl, triethylenediamine, ethylenediamine, and 1,10-phenanthroline) at 200 °C results in the crystallization of a series of layered uranium diphosphonate compounds, [C10H9N2]{UO2(H2O)[CH2(PO3)(PO3H)]} (Ubip2), [C6H14N2]{(UO2)2[CH2(PO3)(PO3H)]2·2H2O} (UDAB), [C2H10N2]2{(UO2)2(H2O)2[CH2(PO3)2]2·0.5H2O} (Uethyl), and [C12H9N2]{UO2(H2O)[CH2(PO3)(PO3H)]} (Uphen). The crystal structures of the compounds are based on UO7 units linked by methylenediphosphonate molecules to form two-dimensional anionic sheets in Ubip2 and UDAB, and one-dimensional anionic chains in Uethyl and Uphen, which are charge balanced by protonated amine molecules. Interaction of the amine molecules with phosphonate oxygens and water molecules results in extensive hydrogen bonding in the interlayer. These amine molecules serve both as structure-directing agents and charge-balancing cations for the anionic uranium phosphonate sheets and chains in the formation of the different coordination geometries and topologies of each structure. Reported herein are the syntheses, structural and spectroscopic characterization of the synthesized compounds.

Three Ba{sup 2+}/UO{sub 2}{sup 2+} methylenediphosphonates have been prepared from mild hydrothermal treatment of uranium trioxide, methylendiphosphonic acid (C1P2) with barium hydroxide octahydrate, barium iodate monohydrate, and small aliquots of HF at 200 Degree-Sign C. These compounds, Ba[UO{sub 2}[CH{sub 2}(PO{sub 3}){sub 2}]{center_dot}1.4H{sub 2}O (Ba-1), Ba{sub 3}[(UO{sub 2}){sub 4}(CH{sub 2}(PO{sub 3}){sub 2}){sub 2}F{sub 6}]{center_dot}6H{sub 2}O (Ba-2), and Ba{sub 2}[(UO{sub 2}){sub 2}(CH{sub 2}(PO{sub 3}){sub 2})F{sub 4}]{center_dot}5.75H{sub 2}O (Ba-3) all adopt layered structures based upon linear uranyl groups and disphosphonate molecules. Ba-2 and Ba-3 are similar in that they both have UO{sub 5}F{sub 2} pentagonal bipyramids that are bridged and chelated by the diphosphonate moiety into a two-dimensional zigzag anionic sheet (Ba-2) and a one-dimensional ribbon anionic chain (Ba-3). Ba-1, has a single crystallographically unique uranium metal center where the C1P2 ligand solely bridges to form [UO{sub 2}[CH{sub 2}(PO{sub 3}){sub 2}]{sup 2-} sheets. The interlayer space of the structures is occupied by Ba{sup 2+}, which, along with the fluoride ion, mediates the structure formed and maintains overall charge balance. - Graphical abstract: Illustration of the stacking of the layers in Ba{sub 3}[(UO{sub 2}){sub 4}(CH{sub 2}(PO{sub 3}){sub 2}){sub 2})F{sub 6}]{center_dot}6H{sub 2}O viewed along the c-axis. The structure is constructed from UO{sub 7} pentagonal bipyramidalmore » units, U(1)O{sub 7}=gray, U(2)O{sub 7}=yellow, barium=blue, phosphorus=magenta, fluorine=green, oxygen=red, carbon=black, and hydrogen=light peach. Highlights: Black-Right-Pointing-Pointer The polymerization of the UO{sub 2}{sup 2+} sites to form uranyl dimers leads to structural variations in compounds. Black-Right-Pointing-Pointer Barium cations stitch uranyl diphosphonate anionic layers together, and help mediate structure formation. Black-Right-Pointing-Pointer HF acts as both a mineralizing agent and a ligand.« less

The hydrothermal reaction of PuO(2) with CH(2)(PO(3)H(2))(2) results in the formation of alpha-Pu[CH(2)(PO(3))(2)](H(2)O), beta-Pu[CH(2)(PO(3))(2)](H(2)O) (1), gamma-Pu[CH(2)(PO(3))(2)](H(2)O) (2), and Pu[CH(2)(PO(3))(2)](H(2)O).H(2)O (3) as crystalline compounds with blue, green, red, and very pale peach coloration, respectively. In all cases single crystal X-ray diffraction studies reveals Pu(4+) coordinated by [CH(2)(PO(3))(2)](4-) and water to yield PuO(7) units. The methylenediphosphonate anions bridge between these units to yield three-dimensional networks. Bond-valence parameters of R(o) = 2.068 and b = 0.385 have been derived for Pu(4+) using a combination of the data reported in this work with that available in crystallographic databases. UV-vis-NIR spectroscopic measurements demonstrate that despite the dramatic color differences all of the compounds contain Pu(4+), and that subtle changes in the visible region of the spectra account for different colors.

A variety of transuranium phosphonates have now been prepared and structurally characterized allowing for comparisons to be made with other metal ions that have been proposed to be surrogates for transuranics (e.g., Zr4+, Ce4+, Th4+, and U4+). The phosphonates that will be discussed in this work include Np(CH3PO3)(CH3PO3H)(NO3)(H2O)·H2O, Pu(CH3PO3)2, M[CH2(PO3)2](H2O)n (M=Ce, Th, U, Np, Pu; n = 0 − 2), and UO2An(H2O)2[CH2(PO3)(PO3H)]2 (An = Th, Np, Pu). Through the examination of these structures, rare coordination geometries for actinides have been uncovered. Simple periodic trends based solely on ionic radii are absent. However, there are examples where surrogate elements adopt the same composition and structure as transuranics, such as Pu(CH3PO3)2 versus Zr(CH3PO3)2.

Three binuclear copper(II) complexes were characterized as solids by X-ray diffraction and in solution by UV/vis spectrophotometric titration, and subsequently evaluated for their glycosidase-like activity. The structure analysis revealed comparable intermetallic Cu...Cu distances (approximately 3.5 A) for the complexes 2 and 3. Despite this similarity, the composition of the complexes differs significantly in aqueous solution as revealed by spectrophotometric titrations. The hydrolysis of selected nitrophenylglycopyranosides is up to 11,000-fold accelerated over background in the presence of the copper(II) complexes in 3-(cyclohexylamino)-1-propanesulfonic acid (CAPS) buffer at pH 10.5 and 30 degrees C.

Reported are four iron(II) complexes with N-benzyl-N,N′-bis(2-pyridylmethyl)-1,2-ethanediamine (LH) and three electronically modified derivatives: N-(4-methoxy)benzyl-N,N′-bis(2-pyridylmethyl)-1,2-ethanediamine (LOMe), N-(4-chloro)benzyl-N,N′-bis(2-pyridylmethyl)-1,2-ethanediamine (LCl), and N-(4-nitro)benzyl-N,N′-bis(2-pyridylmethyl)-1,2-ethanediamine ( L NO 2 ). The four ligands react with FeCl2 to form a series of mononuclear species with the general formula [Fe(LR)Cl2]. The cis-α conformation of the ligand places the amine N-donors trans to the Fe–Cl bonds. The identity of the 4-benzyl substituent has profound influences on the lengths of the iron-ligand bonds, the optical spectra, and the redox activities of the [Fe(LR)Cl2] compounds.

In order to assess the changes in the redox activity of a metal ion that result from inductive effects, three electronically modified derivatives of the ligand, N-benzyl-N,N′-bis(2-pyridylmethyl)-1,2-ethanediamine (LH), have been prepared: N-(4-nitro)benzyl-N,N′-bis(2-pyridylmethyl)-1,2-ethanediamine (LNO2), N-(4-chloro)benzyl-N,N′-bis(2-pyridylmethyl)-1,2-ethanediamine (LCl), and N-(4-methoxy)benzyl-N,N′-bis(2-pyridylmethyl)-1,2-ethanediamine (LOMe). Due to the lack of a fully conjugated π-system between the 4-benzyl substituent and the N-donors, the electronic perturbation should influence a bound metal ion’s redox properties through primarily inductive pathways. The organic ligands react with MnCl2 to form mononuclear complexes with the general formula [Mn(LR)Cl2]. The parent ligand, LH, and its three derivatives each coordinate Mn(II) ions in a cis-α conformation, with the amine N-donors installed trans to the Mn–Cl bonds. Despite its distance from the metal ion, the electron-donating or – withdrawing group has a notable impact on both the metrical parameters of the Mn(II) compounds and the Mn(III/II) reduction potential. A single inductive perturbation can vary the reduction potential by as much as 50 mV.

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).

The hydrothermal reactions of both PuO(2)(2+) and PuO(2) with phosphonates results in the formation of Pu(IV) phosphonates. Pu(CH(3)PO(3))(2), Pu[CH(2)(PO(3))(2)](H(2)O), and UO(2)Pu(H(2)O)(2)[CH(2)(PO(3))(PO(3)H)](2) have been isolated from these reactions and structurally characterized. Pu(CH(3)PO(3))(2) contains six-coordinate Pu(IV) and adopts a structure closely related to that of alpha-Zr(HPO(4))(2). Pu[CH(2)(PO(3))(2)](H(2)O) forms a novel three-dimensional network with seven-coordinate Pu(IV) and chelating/bridging [CH(2)(PO(3))(2)](4-) anions. The heterobimetallic U(VI)/Pu(IV) diphosphonate, UO(2)Pu(H(2)O)(2)[CH(2)(PO(3))(PO(3)H)](2), also forms a three-dimensional network. To complete the An[CH(2)(PO(3))(2)](H(2)O)(n) (An = Th, U, Np, Pu; n = 1, 2) and UO(2)An(H(2)O)(2)[CH(2)(PO(3))(PO(3)H)](2) series, Th[CH(2)(PO(3))(2)](H(2)O)(2) and UO(2)Th(H(2)O)(2)[CH(2)(PO(3))(PO(3)H)](2) have also been prepared. These compounds are isostructural with their Np(IV) analogues.

A lamellar neptunium(IV) methylphosphonate, Np(CH3PO3)(CH3PO3H)(NO3)(H2O)·H2O, has been prepared under hydrothermal conditions via the in situ reduction of NpVI to NpIV. The single crystal structure of this compound shows polar layers that are joined to one another via a hydrogen-bonding network involving interlayer water molecules. Magnetic susceptibility measurements demonstrate that the NpIV ions are magnetically isolated from one another.