Bidentate Linkage Research Articles

Poly[diethylenetriammonium [aquadi-μ2-sulfato-sulfatocerium(III)

A new organically templated open-framework cerium sulfate, {(C4H16N3)[Ce(SO4)3(H2O)]}n, was hydro­thermally synthesized. The CeIII cation is nine-coordinated by nine O atoms, including one water mol­ecule. Two of the SO4 groups afford one monodentate and bidentate linkages as the bridge to connect adjacent CeIII cations, while the third SO4 group attaches the CeIII cation in a bidentate mode. The crystal structure consists of layers composed of eight-membered-ring networks formed by four CeO9 polyhedra and four SO4 tetra­hedra. The triply protonated diethyl­enetriamine cations are located between adjacent layers and connect the layers via hydrogen bonds.

Metal−Organic Frameworks with Functional Pores for Recognition of Small Molecules

Molecular recognition, an important process in biological and chemical systems, governs the diverse functions of a variety of enzymes and unique properties of some synthetic receptors. Because molecular recognition is based on weak interactions between receptors and substrates, the design and assembly of synthetic receptors to mimic biological systems and the development of novel materials to discriminate different substrates for selective recognition of specific molecules has proved challenging. The extensive research on synthetic receptors for molecular recognition, particularly on noncovalent complexes self-assembled by hydrogen bonding and metal-organic coordination, has revealed some underlying principles. In particular, these studies have demonstrated that the shapes of the supramolecular receptors play significant roles in their specific and selective recognition of substrates: receptors can offer concave surfaces that complement their convex targets. This Account describes our research to develop a synthetic molecular recognition platform using porous metal-organic frameworks (MOFs). These materials contain functional pores to direct their specific and unique recognition of small molecules through several types of interactions: van der Waals interactions of the framework surface with the substrate, metal-substrate interactions, and hydrogen bonding of the framework surface with the substrate. These materials have potential applications for gas storage, separation, and sensing. We demonstrate a simple strategy to construct a primitive cubic net of interpenetrated microporous MOFs from the self-assembly of the paddle-wheel clusters M(2)(CO(2))(4) (M = Cu(2+), Zn(2+), and Co(2+)) with two types of organic dicarboxylic acid and pillar bidentate linkers. This efficient method allows us to rationally tune the micropores to size-exclusively sort different small gas molecules, leading to the highly selective separation and purification of gases. By optimizing the strong interactions between open metal sites within porous MOFs and gas molecules such as hydrogen and acetylene, we have developed several MOF materials with extraordinary acetylene storage capacity at room temperature. We have also immobilized Lewis acidic and basic sites into luminescent porous MOFs to recognize and sense neutral and ionic species. Using the strategy to systematically immobilize different open metal sites within porous MOFs from the metalloligand precursors, we have developed the first microporous mixed-metal-organic framework (M'MOF) with enhanced affinity for hydrogen molecules, which successfully separated D(2) from H(2) using kinetic isotope quantum molecular sieving. Because we can functionalize the pores to direct their specific recognition of small molecules, the emerging porous MOFs serve as novel functional materials for gas storage, separation, heterogeneous catalysis, and sensing.

A 4-connected 3D porous coordination polymer with a binodal 6284 net built on tetrahedral quadridentate and bidentate linkers

An unprecedented 4-connected metal–organic framework [Zn2(tpom)(bdc)2]·2H2O (tpom = tetrakis(4-pyridyloxymethylene)methane, bdc = benzene-1,4-dicarboxylic acid) with a binodal 6284 net has been solvothermally synthesized from the assembly of a semirigid tetrahedral ligand (tpom) and a rigid linear bidentate ligand (bdc). The network of 1 is constructed by tetrahedrally connected tpom ligands and metal sites, in which 1D chains [Zn(bdc)]n interweave 2D diamondlike sheets [Zn2(tpom)]n into a 3D porous framework with a binodal 6284 net. 1 has a relatively high thermal stability and exhibits permanent porosity.

Sulfate encapsulation in three-fold interpenetrated metal–organic frameworks with bis(pyridylurea) ligands

Self-assembly of two flexible bis-pyridylurea ligands, pentane-1,5-diylbis(3-pyridin-3-ylurea) (L5) and hexane-1,6-diylbis(3-pyridin-3-ylurea) (L6) with ZnSO4 or CdSO4 (metal-to-ligand molar ratio 1 : 2) results in three metal–organic frameworks with (4,4) net structures, {[ML2(H2O)2]SO4·2H2O}n (1: Zn, L5; 2: Cd, L5; and 3: Zn, L6). Single-crystal X-ray diffraction analyses reveal that all the compounds are characteristic of a 3-fold parallel interpenetrated framework with cavities suitable for encapsulating the sulfate anion despite the different spacer lengths ((CH2)5 and (CH2)6) of the two ligands and variation of the metal ions. The ligand adopts an anti–anti conformation and functions as a bridging bidentate linker, while the sulfate ion is selectively bound by four urea functionalities via multiple hydrogen bonds.

An attenuated total reflectance IR study of silicic acid adsorbed onto a ferric oxyhydroxide surface

Silicic acid (H 4SiO 4) can have significant effects on the properties of iron oxide surfaces in both natural and engineered aquatic systems. Understanding the reactions of H 4SiO 4 on these surfaces is therefore necessary to describe the aquatic chemistry of iron oxides and the elements that associate with them. This investigation uses attenuated total reflectance infrared spectroscopy (ATR-IR) to study silicic acid in aqueous solution and the products formed when silicic acid adsorbs onto the surface of a ferrihydrite film in 0.01 M NaCl at pH 4. A spectrum of 1.66 mM H 4SiO 4 at pH 4 (0.01 M NaCl) has an asymmetric Si–O stretch at 939 cm −1 and a weak Si–O–H deformation at 1090 cm −1. ATR-IR spectra were measured over time (for up to 7 days) for a ferrihydrite film (≈1 mg) approaching equilibrium with H 4SiO 4 at concentrations between 0.044 and 0.91 mM. Adsorbed H 4SiO 4 had a broad spectral feature between 750 and 1200 cm −1 but the shape of the spectra changed as the amount of H 4SiO 4 adsorbed on the ferrihydrite increased. When the solid phase Si/Fe mole ratio was less than ≈0.01 the ATR-IR spectra had a maximum intensity at 943 cm −1 and the spectral shape suggests that a monomeric silicate species was formed via a bidentate linkage. As the solid phase Si/Fe mole ratio increased to higher values a discrete oligomeric silicate species was formed which had maximum intensity in the ATR-IR spectra at 1001 cm −1. The spectrum of this species suggests that it is larger than a dimer and it was tentatively identified as a cyclic tetramer. A small amount of a polymeric silica phase with a broad spectral feature centered at ≈1110 cm −1 was also observed at high surface coverage. The surface composition was estimated from the relative contribution of each species to the area of the ATR-IR spectra using multivariate curve resolution with alternating least squares. For a ferrihydrite film approaching equilibrium with 0.044, 0.14, 0.40 and 0.91 mM H 4SiO 4 the area of the spectra accounted for by monomeric species were 92%, 49%, 23% and 6%, respectively. The remainder was oligomer apart from a small amount (<5%) of polymerized silica at the two higher H 4SiO 4 concentrations. The solid phase Si/Fe mole ratios for these samples were 0.020, 0.037, 0.071 and 0.138, respectively.

Organic Compound/Metal Oxide Hybrid Thin Film Prepared by the Liquid Phase Deposition Method

Organic compound/metal oxide composite thin films have been prepared by the liquid-phase deposition method in one-step deposition technique. Organic dyes were added to the metal fluoro-complexes aqueous solution in order to entrap these dyes within the growing thin films of metal oxides, yielding organic dye/metal oxide hybrid materials. According to Raman spectroscopy and X-ray photoelectron spectroscopy, the formation of the materials in the case of cationic dyes can be explained by electrostatic interaction between negative charge density at the fluorinated surface of metal oxides and the cationic dyes. UV-Vis results indicate that stilbazo and pyrocatechol violet (catecholate dye molecules) form a charge transfer complex with metal oxides through the catechol moiety with a bidentate linkage.

Organic compound/metal oxide hybrid thin film prepared by the liquid phase deposition method

Organic compound/metal oxide composite thin films have been prepared by the liquid-phase deposition method in a one-step deposition technique. Organic dyes were added to the metal fluoro-complexes aqueous solution in order to entrap these dyes within the growing thin films of metal oxides, yielding organic dye/metal oxide hybrid materials. According to Raman spectroscopy and X-ray photoelectron spectroscopy, the formation of the materials in the case of cationic dyes can be explained by the electrostatic interaction between negative charge density at the fluorinated surface of metal oxides and the cationic dyes. UV-Vis results indicate that stilbazo and pyrocatechol violet (catecholate dye molecules) form a charge transfer complex with metal oxides through the catechol moiety with a bidentate linkage.

Photovoltaic Performance of Nanoporous TiO2 Replicas Synthesized from Mesoporous Materials for Dye-Sensitized Solar Cells

For dye-sensitized solar cell (DSSC), highly ordered nanoporous TiO2 materials with crystalline frameworks were successfully synthesized from different silica templates including SBA-15, KIT-6 and MSU-H. A photoelectrode in DSSC was fabricated by adsorbing cis-bis(isothiocyanato)bis(2,2'-bipyridyl-4,4'-dicarboxylato)-ruthenium(II)bis-tetrabutylammonium dye (N719) onto the prepared TiO2 nanoparticles. The samples were characterized by XRD, TEM, FE-SEM, AFM and Brunauer-Emmett-Teller (BET), and FT-IR analysis. An investigation of the influence of the bonding structure of N719 dye and nanoporous TiO2 on the photovoltaic performance of DSSC revealed that the bonding structure of N719 on TiO2 films is caused by the unidentate and bidentate linkage. Based on the overall conversion efficiency (eta), fill factor (FF), open-circuit voltage (V(oc)) and short-circuit current (/sc) from the I-V curves measured, it was observed that the photoelectric performance is strongly dependent on the dispersion properties of the nanoporous TiO2 replicas from mesoporous silica templates.

Efficient, Stable Infrared Photovoltaics Based on Solution-Cast Colloidal Quantum Dots

Half of the sun's power lies in the infrared. As a result, the optimal bandgaps for solar cells in both the single-junction and even the tandem architectures lie beyond 850 nm. However, progress in low-cost, large-area, physically flexible solar cells has instead been made in organic and polymer materials possessing absorption onsets in the visible. Recent advances have been achieved in solution-cast infrared photovoltaics through the use of colloidal quantum dots. Here we report stable solution-processed photovoltaic devices having 3.6% power conversion efficiency in the infrared. The use of a strongly bound bidentate linker, benzenedithiol, ensures device stability over weeks. The devices reach external quantum efficiencies of 46% in the infrared and 70% across the visible. We investigate in detail the physical mechanisms underlying the operation of this class of device. In contrast with drift-dominated behavior in recent reports of PbS quantum dot photovoltaics, we find that diffusion of electrons and holes over hundreds of nanometers through our PbSe colloidal quantum dot solid is chiefly responsible for the high external quantum efficiencies obtained in this new class of devices.

A Computational Study on π and σ Modes of Metal Ion Binding to Heteroaromatics (CH)5-mXm and (CH)6-mXm (X = N and P): Contrasting Preferences Between Nitrogen- and Phosphorous-Substituted Rings

The pi and sigma complexation energy of various heteroaromatic systems which include mono-, di-, and trisubstituted azoles, phospholes, azines and phosphinines with various metal ions, viz. Li(+), Na(+), K(+), Mg(2+), and Ca(2+), was calculated at the post Hartree-Fock MP2 level, MP2(FULL)/6-311+G(2d,2p)//MP2/6-31G. The azoles and azines were found to form stronger sigma complexes than the corresponding pi complexes, whereas the phospholes and phosphinines had higher pi complexation energy with Li(+), Mg(2+), and Ca(2+) while their pi and sigma complexation energies were very comparable with Na(+) and K(+). The strongest pi complex among the five-membered heteroaromatic system was that of pyrrole with all the metals except with Mg(2+), while benzene formed the strongest pi complex among the six-membered heterocyclic systems. The nitrogen heterocyclic system 4H-[1,2,4] triazole and pyridazine formed the strongest sigma complex among the five- and six-membered heteroaromatic systems considered. The complexation energy of the pi and sigma complexes of the azoles and azines was found to decrease with the increase in the heteroatom substitution in the ring, while that of phospholes and phosphinines did not vary significantly. The azoles and azines preferred to form sigma complexes wherein the metal had bidentate linkage, while the phospholes and phosphinines did not show binding mode preference. In the sigma complexes of both azoles and phospholes, the metal binds away form the electron-deficient nitrogen or phosphorus center.

Spirocyclic Sulfur and Selenium Ligands as Molecular Rigid Rods in Coordination of Transition Metal Centers

A set of analogous chalcogen-containing spirocycles, 2,6-dithiaspiro[3.3]heptane, 2,6-diselenaspiro[3.3]heptane, and 2-thia-6-selenaspiro[3.3]heptane [E(2)C(5)H(8), E = S (1), Se (2), and S/Se (3)], has been prepared and fully characterized by spectroscopic methods and by X-ray diffraction. The structural characterization of 2 was presented by us earlier, while the crystal structures of 1 and 3 are reported here for the first time. Molecules 1-3 are built around the central tetrahedral carbon atom and therefore are nonplanar. The E...E separation ranges from 4.690(1) A in 1 to 4.906(1) A in 2. Molecule 3 has statistically mixed positions of sulfur and selenium atoms in the solid state with all geometric characteristics being intermediate between those of 1 and 2. Compounds 2 and 3 have been tested as molecular rigid rod ligands in coordination reactions with transition metal complexes such as Cu(hfac)(2) (4), cis-Co(hfac)(2).2H(2)O (5), and cis-Ni(hfac)(2).2H(2)O (6) (hfac = hexafluoroacetylacetonate). Several coordination products built of two building blocks, M(hfac)(2) (M = Cu, Co, and Ni) and Se(2)C(5)H(8) (2), have been prepared in crystalline form and structurally characterized. The copper-based product (7) is comprised of the oligomeric units {[Cu(hfac)(2)](3).2mu(2)-Se(2)C(5)H(8)-Se,Se'} built on the axial Cu...Se interactions averaged at 2.909 A. These units are further assembled into 1D polymeric chains via intermolecular Cu...F contacts at 2.829 A. The SSeC(5)H(8) (3) ligand was also used in the reaction with Cu(hfac)(2) to afford an analogue of 7, namely {[Cu(hfac)(2)](3).2mu(2)-SSeC(5)H(8)-S,Se} (8). Complex 8 exhibits statistically mixed positions of the donor sulfur and selenium atoms to give an average axial Cu...S/Se contact at 2.892 A. In contrast to the copper complexes of composition 3:2, the stoichiometries of the isolated cobalt and nickel products are 1:1, [M(hfac)(2).Se(2)C(5)H(8)] (M = Co (9) and Ni (10)). Complexes 9 and 10 exhibit 1D polymer structures having alternating metal units cis-M(hfac)(2) and ligands 2 with intermolecuar M...Se separations of 2.6046(8) and 2.5523(16) A, respectively. In all products 7-10 the initial cis or trans geometry of M(hfac)(2) complexes is preserved and the spiro[3.3]heptane ligands act as bidentate linkers bridging transition metal centers via both donor ends. The magnetic properties of this series of new Cu(II), Co(II), and Ni(II) complexes have been tested by variable-temperature magnetic susceptibility measurements.

Powder diffraction study of a coordination polymer comprised of rigid building blocks: [Rh2(O2CCH3)4.mu2-Se2C5H8-Se,Se']infinity.

The crystal structure of a new hybrid product comprised of two rigid building blocks, namely dirhodium(II) tetraacetate, [Rh(2)(O(2)CCH(3))(4)] (1), and 2,6-diselenaspiro[3.3]heptane, Se(2)C(5)H(8) (2), has been solved ab initio using laboratory source X-ray powder diffraction (XRPD) data. The rigid body refinement approach has been applied to assist in finding an adequate model and to reduce the number of the refined parameters. Complex [Rh(2)(O(2)CCH(3))(4).mu(2)-Se(2)C(5)H(8)-Se,Se'] (3) conforms to the triclinic unit cell with lattice parameters of a = 8.1357(4), b = 8.7736(4), and c = 15.2183(8) A, alpha = 77.417(3), beta = 88.837(3), and gamma = 69.276(4) degrees, V = 989.66(8) A(3), and Z = 2. The centrosymmetric P space group was selected for calculations. The final values of the reduced wR(p), R(p), and chi(2) were calculated at 0.0579, 0.0433, and 5.95, respectively. The structure of 3 is a one-dimensional zigzag polymer built on axial Rh...Se interactions at 2.632(6) A. The 2,6-diselenaspiro[3.3]heptane ligand acts as a bidentate linker bridging dirhodium units via both selenium atoms. The geometrical parameters of individual groups for rigid body refinement have been obtained from X-ray powder data for dirhodium(II) tetraacetate (1) and from single-crystal X-ray diffraction for diselenium molecule 2. The crystal structures of 1 and 2 are reported here for the first time. For 1 indexing based on XRPD data has resulted in the triclinic unit cell P with lattice parameters of a = 8.3392(7), b = 5.2216(5), and c = 7.5264(6) A, alpha = 95.547(10), beta = 78.101(6), and gamma = 104.714(13) degrees, V = 309.51(5) A(3), and Z = 1. The final values were wR(p) = 0.0452, R(p) = 0.0340, and chi(2) = 1.99. The 1D polymeric motif built on axial Rh.O interactions of the centrosymmetric dirhodium units has been confirmed for the solid-state structure of 1. Compound 2,6-diselenaspiro[3.3]heptane (2) conforms to the monoclinic space group P2(1)/c with the unit cell parameters of a = 5.9123(4), b = 19.6400(13), and c = 5.8877(4) A, beta = 108.5500(10) degrees, V = 648.15(8) A(3), and Z = 4.

Pentapotassium sodium hexasulfatodicerate(III)

K5Na[Ce2(SO4)6] contains two CeIII ions, cross-linked via two oxygen and four sulfate bridges, a unique configuration for cerium sulfates. Each cerium is (8 + 2)-coordinated by O atoms of four sulfate groups by bidentate linkages.

Mineralogical characterization of arsenic in uranium mine tailings precipitated from iron-rich hydrometallurgical solutions.

Arsenic-rich uranium mine tailings from the Rabbit Lake in-pit tailings management facility (RLITMF) in northern Saskatchewan, Canada, were investigated to determine the mineralogy and long-term stability of secondary arsenic precipitates formed from iron-rich hydrometallurgical solutions. Total arsenic and iron concentrations in six iron-rich samples of the mine tailings ranged from 56 to 6,000 microg/g and from 12 600 to 30 200 microg/g, respectively (Fe/As molar ratios of 5.3-303). On the basis of stability field diagrams generated from pH, Eh, and temperature measurements on tailings samples (mean values of 9.79, +162 mV, and 2.8 degrees C, respectively), it was concluded that arsenic and iron in the tailings were stable as As5+ and Fe3+. Synchrotron-based X-ray absorption spectroscopic studies of tailings samples, fresh mill precipitates, and reference compounds showed that the arsenic in iron-rich areas of the tailings existed as the stable As5+ and was adsorbed to 2-line ferrihydrite through inner-sphere bidentate linkages. Furthermore, under the conditions in the RLITMF, the 2-line ferrihydrite did not undergo any measurable conversion to more crystalline goethite or hematite, even in tailings discharged to the RLITMF 10 yr prior to sampling.

Genotoxicity of musk ketone

Thermal stabilities of perfluoropolyethers, Fomblin Z, Fomblin Y, Krytox, and Demnum in the presence of Al2O3 were examined. Fomblin Z was found to degrade at 200°C in two stages, the slow first stage, and the vigorous second stage leading to complete loss of fluid. It is concluded that oxide-to-halide conversion occurs on Al2O3 surface during the first stage. The second stage is attributed to a catalytic process induced by Lewis acid AlF3. Based on NMR and mass spectroscopic evidences the following reaction mechanism is advanced for the second stage: (1) a bidentate linkage is formed between an acidic aluminum and two oxygen atoms of an acetal unit (-O-CF2-O-) of Fomblin Z chains, and (2) the partial positive charge thus developed at the acetal carbon induces a fluorine atom transfer from the adjacent CF2 unit onto the acetal carbon and results in chain scission with transformation of the acetal sector into a methoxy end-group (-O-CF3) and the adjacent unit into either an acylfluoride end-group (FCO-CF2-), or a fluoroformate end-group (FCO-O-CF2-). Lacking acetal units Krytox and Demnum are stable against this degradation process. In the case of Fomblin Y, owing to the paucity of acetal units, no reaction was observed when heated in the presence of Al2O3; when heated with AlCl3, removal of acetal units and consequential formation of functional end-groups were observed.

Vibrational spectroscopic studies of uranyl complexes in aqueous and non-aqueous solutions

Vibrational spectra have been obtained for aqueous solution of uranyl-perchlorates, -fluorides, -chlorides, -acetates and -sulphates over a range of solution composition with added anions. We have prepared [Bu n 4N][UO 2Cl 4], [Me 4N][UO 2Cl 4], [Pr n 4N][[UO 2(NO 3) 3], [Bu n 4N][UO 2(NO 3) 3], with the expectation that the large cation would give a better approximation to vibrational frequencies of the free anion and would allow measurements in non-coordinating solvents. As the perchlorate is not coordinated to [UO 2] 2+ in aqueous solution the expected structure is a solvated cation [UO 2(OH 2) 5] 2+ with characteristic infrared 962.5, 253 and 160 cm −1 and Raman 874 and 198 cm −1 bands. The formation of weak, solvated [UO 2X] + complexes (X=F, Cl) has been established with frequencies at 908, 827, 254, 380 cm −1 and 956, 871, 254 and 222 cm −1 for [UO 2F] + and [UO 2Cl] +, respectively. Bidentate NO 3 coordination has been established for solid and dissolved (in CH 2Cl 2) [R 4N][UO 2(NO 3) 3] (R=Pr n , Bu n ). Aqueous solutions of UO 2(NO 3) 2 and Cs[UO 2(NO 3) 3] show no clear evidence that bidentate or monodentate nitrate is present. Both unidentate and bidentate linkage of acetate-uranyl were established for acetate complexes in aqueous solutions. For the uranyl sulphate system, monodentate sulphate coordination is the major mode at low SO 4:U ratios, and even at a ratio of 3:1 there is very little free sulphate.

Degradation of perfluoropolyethers catalyzed by aluminum oxide

Thermal stabilities of perfluoropolyethers, Fomblin Z, Fomblin Y, Krytox, and Demnum in the presence of Al 2O 3 were examined. Fomblin Z was found to degrade at 200°C in two stages, the slow first stage, and the vigorous second stage leading to complete loss of fluid. It is concluded that oxide-to-halide conversion occurs on Al 2O 3 surface during the first stage. The second stage is attributed to a catalytic process induced by Lewis acid AlF 3. Based on NMR and mass spectroscopic evidences the following reaction mechanism is advanced for the second stage: (1) a bidentate linkage is formed between an acidic aluminum and two oxygen atoms of an acetal unit (-O-CF 2-O-) of Fomblin Z chains, and (2) the partial positive charge thus developed at the acetal carbon induces a fluorine atom transfer from the adjacent CF 2 unit onto the acetal carbon and results in chain scission with transformation of the acetal sector into a methoxy end-group (-O-CF 3) and the adjacent unit into either an acylfluoride end-group (FCO-CF 2-), or a fluoroformate end-group (FCO-O-CF 2-). Lacking acetal units Krytox and Demnum are stable against this degradation process. In the case of Fomblin Y, owing to the paucity of acetal units, no reaction was observed when heated in the presence of Al 2O 3; when heated with AlCl 3, removal of acetal units and consequential formation of functional end-groups were observed.

Preparation and Physico-Chemical Studies of Some 3-Substituted-2,4-pentanedionato Copper(II) Complexes and Their Adducts

Abstract The copper(II) complexes of 3-phenyl-, 3-benzyl-, 3-chloro-, and 3-nitro-2,4-pentanediones and their 2,2′-bipyridine and 1,10-phenanthroline adducts have been prepared and characterised by microanalysis, conductance, magnetic and spectral measurements. The available conductance data in nitromethane indicate that the complexes are nonelectrolytes while the room temperature magnetic moments suggest that they are magnetically dilute compounds. The shifts observed in the ligand field spectral bands and the solvent dependence suggest plausible 4-, 5- and 6-coordinate geometries for these compounds. The infra-red spectral shifts inferred the possibility of O-unidentate β-diketonate linkage and bidentate linkage of base. Square-planar and square-pyramidal stereochemistries have been proposed for the complexes and adducts, respectively, except for Cu(Cl-acac)2.bipy2 which is 6-coordinate octahedral.

Bidentate linkage isomerization and phosphate hydrolysis in (triphosphato)tetraamminecobalt(III)

Etude de ces reactions par spectrometrie RMN de 31 P et visible. Parametres thermodynamiques

Mid-, far-infrared and raman spectra of uranyl complexes in aqueous solutions

Vibrational spectra have been obtained for aqueous solution of UO 2C10 4, Na 3[UO 2F 5], [NH 4] 3[UO 2F 5], UO 2F 2, [Bu 4N] 2[UO 2Cl 4], UO 2Cl 2, UO(NO 3) 2, Rb [UO 2(NO 3) 3], [Pr 4N] [UO 2(NO 3) 3], UO 2(O 2CCH 3) 2, [Pr 4N] [UO 2(O 2CCH 3) 3] and UO 2SO 4 over a range of solution composition. The residual absorptions of H 2O after water subtraction suggest that some water molecules are bound to [UO 2] 2+. There was no evidence of perchlorate coordination, but besides solvated [UO 2] 2+ ion formation of weak [UO 2F] + and [UO 2Cl] + complexes have been established. The four nitrate stretching features do not refer neither to bidentate nor to monodentate ligand, but both monodentate and bidentate linkage of acetate to uranyl were established for acetate complexes. The main species present in UO 2SO 4 solution can be ascribed to a monodentate sulphate. From uranyl frequencies force constants and UO bond distances were calculated for solvated complexes.