Syntheses, structures, and electrochemistry of a dinuclear compound and a mononuclear-mononuclear cocrystalline compound of uranyl(VI) (original) (raw)
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Inorganic Chemistry, 2010
The U VI complex with a pentadentate Schiff base ligand (N,N 0 -disalicylidenediethylenetriaminate = saldien 2-) was prepared as a starting material of a potentially stable U V complex without any possibility of U V O 2 þ 3 3 3 U V O 2 þ cation-cation interaction and was found in three different crystal phases. Two of them had the same composition of U VI O 2 -(saldien) 3 DMSO in orthorhombic and monoclinic systems (DMSO = dimethyl sulfoxide, 1a and 1c, respectively). The DMSO molecule in both 1a and 1c does not show any coordination to U VI O 2 (saldien), but it is just present as a solvent in the crystal structures. The other isolated crystals consisted only of U VI O 2 (saldien) without incorporation of solvent molecules (1b, orthorhombic). A different conformation of the coordinated saldien 2in 1c from those in 1a and 1b was observed. The conformers exchange each other in a solution through a flipping motion of the phenyl rings. The pentagonal equatorial coordination of U VI O 2 (saldien) remains unchanged even in strongly Lewis-basic solvents, DMSO and N,N-dimethylformamide. Cyclic voltammetry of U VI O 2 (saldien) in DMSO showed a quasireversible redox reaction without any successive reactions. The electron stoichiometry determined by the UV-vis-NIR spectroelectrochemical technique is close to 1, indicating that the reduction product of U VI O 2 (saldien) is [U V O 2 (saldien)] -, which is stable in DMSO. The standard redox potential of [U V O 2 (saldien)] -/U VI O 2 (saldien) in DMSO is -1.584 V vs Fc/Fc þ . This U V complex shows the characteristic absorption bands due to f-f transitions in its 5f 1 configuration and charge-transfer from the axial oxygen to U 5þ . Hennig, C.; Tsushima, S.; , K.; Ikeda, Y.; Scheinost, A. C.; Bernhard, G. Inorg. Chem. 2007, 46, 4212-4219. (i) Grenthe, I.; Fuger, J.; Konings, R. J. M.; Lemire, R. J.; Muller, A. B.; Nguyen-Trung, C.; Wanner, H.; Forest, I. Chemical Thermodynamics of Uranium; North Holland, Elsevier Science Publishers BV: Amsterdam, The Netherlands, 1992. (j) Fangh€ anel, T.; Neck, V.; Fuger, J.; Palmer, D. A.; Grenthe, I,; Rand, M. H. Update on the Chemical Thermodynamics of Uranium, Neptunium, Plutonium, Americium and Technetium; Elsevier Science BV: Amsterdam, The Netherlands, 2003.
Inorganic Chemistry Communications, 2005
Reaction of K[(OPPh 2) 2 N] with UO 2 (NO 2) 2 AE 6H 2 O resulted in the formation of compound [UO 2 [(OPPh 2) 2 N] 2 ] 3 (1). Single-crystal diffraction analysis of 1 reveals an elaborated and unique trinuclear uranyl compound, where the central UO 2 moiety exhibits Lewis basic properties through an equatorial UÁ Á ÁO@U@OÁ Á ÁU bridging towards two outer uranyl units comprised in a six-membered ring array. The central and outer UO 2 groups are also bridged by means of four eight-membered rings containing the ancillary ligand. The overall morphology of this compound may be regarded as a linear U 3 O 2 core engaging two different types of environments for the uranium atoms.
Inorganica Chimica Acta, 2002
The [1'/1] asymmetric compartmental ligands H 2 L A and H 2 L B , containing a N 3 O 2 Schiff base coordination chamber and an adjacent O 2 O n (n 0/3, 4) crown-like coordination chamber, have been prepared by reaction of equimolar amount of 3,3?-(3oxapentane-1,5-diyldioxy)bis(2-hydroxybenzaldehyde (H 2 L I ) or 3,3?-(3,6-dioxaoctane-1,8-diyldioxy)bis(2-hydroxybenzaldehyde) (H 2 L II ) and 1,5-diamino-3-azamethylpentane. These macrocycles react with UO 2 2' to form the mononuclear complexes [UO 2 (L A )] and [UO 2 (L B )]; the same complexes have been obtained by condensation of the above formyl-and amine-precursors in the presence of UO 2 2' as templating agent. The uranyl(VI) ion invariantly prefers the N 3 O 2 site as evidenced by IR and NMR spectroscopy and confirmed by an X-ray diffractometric investigation for the complex [UO 2 (L A )]. [UO 2 (L A )] crystallizes in the monoclinic space group P 2 1 /c with four formula units in a cell of dimensions a 0/10.412(2), b 0/12.973(3), c 0/19.743(4) Å and b0/ 100.22(3)8. The structure was solved by standard methods and refined by full-matrix least-squares to the conventional R index of 6.9%. The uranyl(VI) atom presents a classic pentagonal bipyramidal coordination polyhedron with the base formed by three nitrogen and two phenolic oxygen atoms of the cyclic ligand. A detailed 1 H and 13 C NMR study was carried out in order to compare the structure in solution with that found in the solid state. #
Low-Dimensional Structural Units in Amine-Templated Uranyl Oxoselenates(VI): Synthesis and Crystal Structures of [C3H12N2](UO2)(SeO4)2(H2O)2, [C5H16N2]2(UO2)(SeO4)2(H2O)2, [C4H12N][(UO2)(SeO4)(NO3)], and [C4H14N2][(UO2)(SeO4)2(H2O
Zeitschrift Fur Anorganische Und Allgemeine Chemie, 2005
The crystals of four amine-templated uranyl oxoselenates(VI), [C3H12N2][(UO2)(SeO4)2(H2O)2](H2O) (1), [C5H16N2]2[(UO2)(SeO4)2(H2O)](NO3)2 (2), [C4H12N][(UO2)(SeO4)(NO3)] (3), and [C4H14N2][(UO2)(SeO4)2(H2O)] (4) were prepared by evaporation from aqueous solution of uranyl nitrate, selenic acid and the respective amine. The crystal structures of all four compounds have been solved by direct methods from X-ray diffraction data. The structure of 1 (triclinic, , a = 7.5611(16), b = 7.7650(17), c = 12.925(3) Å, α = 94.605(18), β = 94.405(17), γ = 96.470(17)°, V = 748.8(3) Å3, R1 = 0.029 for 2769 unique observed reflections) is based upon 0D-units of the composition [(UO2)2(SeO4)4(H2O)4]4−. These discrete units are composed from two pentagonal [UO7]8− bipyramids linked via [SeO4]2− tetrahedra and are unknown in structural chemistry of uranium so far. The structure of 2 (monoclinic, C2/c, a = 28.916(5), b = 8.0836(10), c = 11.9856(16) Å, β = 110.909(11)°, V = 2617.1(6) Å3, R1 = 0.035 for 2578 unique observed reflections) contains [(UO2)(SeO4)2(H2O)]2− chains of corner-sharing pentagonal [UO7]8− bipyramids and [SeO4]2− tetrahedra. The chains run parallel to the c axis and are arranged into layers parallel to (100). In the structure of 3 (monoclinic, C2/m, a = 21.244(5), b = 7.1092(11), c = 8.6581(18) Å, β = 97.693(17)°, V = 1295.8(4) Å3, R1 = 0.027 for 1386 unique observed reflections), pentagonal [UO7]8− bipyramids share corners with three [SeO4]2− tetrahedra each and an edge with a [NO3]− anion to form [(UO2)(SeO4)(NO3)]− chains parallel to the b axis. In the structure of 4 (triclinic, , a = 6.853(2), b = 10.537(3), c = 10.574(3) Å, α = 99.62(3), β = 94.45(3), γ = 100.52(3)°, V = 735.6(4) Å3, R1 = 0.045 for 2713 unique observed reflections), one symmetrically independent pentagonal [UO7]8− bipyramid shares corners with four [SeO4]2− tetrahedra to form the [(UO2)(SeO4)2(H2O)]2− chains parallel to the a axis. A comparison to related uranyl compounds is given.
Scientific Reports, 2016
Two derivatives of organouranyl mononuclear complexes [UO 2 (L)THF] (1) and [UO 2 (L)Alc] (2), where L = (2,2′-(1E,1′E)-(2,2-dimethylpropane-1,3-dyl)bis(azanylylidene, THF = Tetrahydrofuran, Alc = Alcohol), have been prepared. These complexes have been determined by elemental analyses, single crystal X-ray crystallography and various spectroscopic studies. Moreover, the structure of these complexes have also been studied by DFT and time dependent DFT measurements showing that both the complexes have distorted pentagonal bipyramidal environment around uranyl ion. TD-DFT results indicate that the complex 1 displays an intense band at 458.7 nm which is mainly associated to the uranyl centered LMCT, where complex 2 shows a band at 461.8 nm that have significant LMCT character. The bonding has been further analyzed by EDA and NBO. The photocatalytic activity of complexes 1 and 2 for the degradation of rhodamine-B (RhB) and methylene blue (MB) under the irradiation of 500W Xe lamp has been explored, and found more efficient in presence of complex 1 than complex 2 for both dyes. In addition, dye adsorption and photoluminescence properties have also been discussed for both complexes. The chemistry of uranium is dominated by hexavalent uranyl dication (UO 2 2+) which is a linear triatomic species capped with terminal oxygen atoms 1,2. The uranyl ion is remarkably stable form of natural uranium which exists in nuclear fuel processing, and usually exhibits tetragonal, pentagonal, and hexagonal bipyramidal geometries in the equatorial plane 3,4. Furthermore, uranyl dication shows little propensity to involve in various reactions characteristic of its group 6 transition-metal analogues [MO 2 ] 2+. [M = Cr, Mo, W] 5. It is worth mentioning that the transition metal analogues of uranyl dication always adopt bent geometry whereas the uranyl ions are essentially linear with bond angle close to 180°, and are strongly covalent in nature. Moreover, the uranyl ion is almost always found with 4, 5 or 6 ligands coordinated to the uranyl cation in the equatorial plane. Interestingly, the bond lengths to the equatorial ligands are always longer than to the axial uranyl oxygen 6. However, the uranyl complexes with cyclopentadienyl-based ligands exhibit coordination number upto 1-3 7. Salen ligands form neutral complexes with uranyl ion UO 2 2+ in tetradentate fashion in which a fifth coordination site is occupied by additional monodentate ligand such as hard anion or neutral donor molecule or a solvent molecule in equatorial position 8. Interestingly, the presence of solvent molecule at the fifth position in equatorial plane plays a significant role in the activation of the substrate in catalysis 8. Furthermore, Uranyl(VI) complexes exhibit various promising physicochemical properties, such as photoluminescence, photocatalysis, and photochemical reactivity 9. The photoluminescence in uranyl complexs is due to the excitation and relaxation of the UO 2 2+ group. In some cases, the interaction between the ligands and the uranium centers via the "antenna effect" also causes photoluminescence 10. In addition, uranyl complexes have also been reported to have some rare properties like pollutant adsorption properties because of their large surface area and functional groups 11 .
European Journal of Inorganic Chemistry, 2012
The interaction of uranyl nitrate with the series of diamides Et 2 N(C=O)(CH 2) n (C=O)NEt 2 (0 Յ n Յ 6) was investigated to evaluate systematically the effect of the (CH 2) n spacer on the solid-state structures of the corresponding uranyl complexes. Under aerobic conditions, [UO 2 (NO 3) 2 •6H 2 O] reacted with an excess amount of these diamides (L) in organic solvents to yield [UO 2 (κ 2-NO 3) 2 (L)] {1 [n = 0, tetraethyloxalamide (TEOA)], 2 [n = 1, tetraethylmalonamide (TEMA)], 3 [n = 2, tetraethylsuccinamide (TESA)], 5 [n = 3, tetraethylglycolamide (TEGA)], 6 [n = 4, tetraethyladipicamide (TEAA)], 7 [n = 5, tetraethylpimelicamide (TEPA)], and 8 [n = 6, tetraethylsubericamide (TESUA)]}, which were isolated and characterized by 1 H NMR, ESI-MS, IR, and Raman spectroscopy. Under anhydrous and anaerobic conditions, [UO 2 (OTf) 2 ] (OTf = trifluoromethanesulfonate) was treated with an excess amount of L to give [UO 2 (L) 2 ][OTf] 2 , which was isolated for n = 1 (9) and n = 2 (10). The crystal structures of 2,
Inorganic Chemistry, 2006
Na 2 [UO 2 (IO 3) 4 (H 2 O)] has been synthesized under mild hydrothermal conditions. Its structure consists of Na + cations and [UO 2 (IO 3) 4 (H 2 O)] 2anions. The [UO 2 (IO 3) 4 (H 2 O)] 2anions are formed from the coordination of a nearly linear uranyl, UO 2 2+ , cation by four monodentate IO 3anions and a coordinating water molecule to yield a pentagonal bipyramidal environment around the uranium center. The water molecules form intermolecular hydrogen bonds with the terminal oxo atoms of neighboring [UO 2 (IO 3) 4 (H 2 O)] 2anions to yield one-dimensional chains that extend down the b axis. There are two crystallographically unique iodate anions in the structure of Na 2 [UO 2 (IO 3) 4 (H 2 O)]. One of these anions is aligned so that the lone-pair of electrons is also directed along the b axis. The overall structure is therefore polar, owing to the cooperative alignment of both the hydrogen bonds and the lone-pair of electrons on iodate. The polarity of the monoclinic space group C2 (a) 11.3810(12) Å, b) 8.0547(8) Å, c) 7.6515(8) Å,) 90.102(2)°, Z) 2, T) 193 K) found for this compound is consistent with the structure. Secondharmonic generation of 532 nm light from a 1064 nm laser source yields a response of approximately 16× R-SiO 2 .
Inorganic Chemistry, 2013
While uranyl halide complexes [UO 2 (halogen) n ] 2−n (n = 1, 2, 4) are ubiquitous, the tricoordinate species have been relatively unknown until very recently. Here photoelectron spectroscopy and relativistic quantum chemistry are used to investigate the bonding and stability of a series of gaseous tricoordinate uranyl complexes, UO 2 X 3 − (X = F, Cl, Br, I). Isolated UO 2 X 3 − ions are produced by electrospray ionization and observed to be highly stable with very large adiabatic electron detachment energies: 6.25, 6.64, 6.27, and 5.60 eV for X = F, Cl, Br, and I, respectively. Theoretical calculations reveal that the frontier molecular orbitals are mainly of uranyl U−O bonding character in UO 2 F 3 − , but they are from the ligand valence np lone pairs in the heavier halogen complexes. Extensive bonding analyses are carried out for UO 2 X 3 − as well as for the doubly charged tetracoordinate complexes (UO 2 X 4 2− ), showing that the U−X bonds are dominated by ionic interactions with weak covalency. The U−X bond strength decreases down the periodic table from F to I. Coulomb barriers and dissociation energies of UO 2 X 4 2− → UO 2 X 3 − + X − are calculated, revealing that all gaseous dianions are in fact metastable. The dielectric constant of the environment is shown to be the key in controlling the thermodynamic and kinetic stabilities of the tetracoordinate uranyl complexes via modulation of the ligand−ligand Coulomb repulsions.