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.

Comparisons of Pu(IV) and Ce(IV) diphosphonates.

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.

Evaluating binuclear copper(II) complexes for glycoside hydrolysis.

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.

Periodic trends in actinide phosphonates: divergence and convergence between thorium, uranium, neptunium, and plutonium systems.

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.

Further examples of the failure of surrogates to properly model the structural and hydrothermal chemistry of transuranium elements: insights provided by uranium and neptunium diphosphonates.

In situ hydrothermal reduction of Np(VI) to Np(IV) in the presence of methylenediphosphonic acid (C1P2) results in the crystallization of Np[CH2(PO3)2](H2O)2 (NpC1P2-1). Similar reactions have been explored with U(VI) resulting in the isolation of the U(IV) diphosphonate U[CH2(PO3)2](H2O) (UC1P2-1), and the two U(VI) diphosphonates (UO2)2[CH2(PO3)2](H2O)3.H2O (UC1P2-2) and UO2[CH2(PO3H)2](H2O) (UC1P2-3). Single crystal diffraction studies of NpC1P2-1 reveal that it consists of eight-coordinate Np(IV) bound by diphosphonate anions and two coordinating water molecules to create a polar three-dimensional framework structure wherein the water molecules reside in channels. The structure of UC1P2-1 is similar to that of NpC1P2-1 in that it also adopts a three-dimensional structure. However, the U(IV) centers are seven-coordinate with only a single bound water molecule. UC1P2-2 and UC1P2-3 both contain U(VI). Nevertheless, their structures are quite distinct with UC1P2-2 being composed of corrugated layers containing UO 6 and UO 7 units bridged by C1P2; whereas, UC1P2-3 is found as a polar three-dimensional network structure containing only pentagonal bipyramidal U(VI). Fluorescence measurements on UC1P2-2 and UC1P2-3 exhibit emission from the uranyl moieties with classical vibronic fine-structure.

In situ hydrothermal reduction of neptunium(VI) as a route to neptunium(IV) phosphonates.

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.