Chelating Carboxylate Groups Research Articles

Synthesis, crystal structure and thermal decomposition mechanism of complex [Sm( o-MBA) 3phen] 2

The title complex [Sm( o-MBA) 3phen] 2 ( o-MBA, o-methylbenzoate; phen, 1,10-phenanthroline) was prepared and characterized by single crystal X-ray diffraction, elemental analysis, IR spectra and TG-DTG techniques. The results show that the crystal is triclinic, space group P ī with a = 13.1364(10) Å, b = 14.3739(11) Å, c = 17.4356(13) Å; α = 83.1100(10)°, β = 83.7760(10)°, γ = 73.0520(10)°, Z = 2, D c = 1.568 Mg/m 3, F (000) = 1476. The crystal is consisted of two similar types of binuclear molecule. Each Sm 3+ is nine-coordinated by one bidentate chelating carboxylate group, two bidentate bridging and two tridentate chelating-bridging carboxylate groups, as well as one 1,10-phenanthroline molecule. The thermal decomposition mechanism of [Sm( o-MBA) 3phen] 2 has been determined on the basis of thermal analysis. The dependences of E − α for the first-stage decomposition process were determined by using Ozawa-iterative procedure, which show the E values varied with the extent of conversion. In addition, the lifetime equation at weight-loss of 10% was deduced as ln τ = −25.5547 + 18511.68/ T by isothermal thermogravimetric analysis.

Hydrothermal Synthesis and Crystal Structure of a Europium(III) Coordination Polymer with 5-Sulfoisophthalate Trivalent Anions and Free 4,4′-Bipyridine Molecules

A novel europium(III) coordination polymer [Eu(Sip)(H2O)5]n · nH2O · 1.5n(Bipy) (I) (Sip is 5-sulfo-isophthalate trivalent anion and Bipy is 4,4′-bipyridine) is hydrothermally synthesized and determined by the single crystal X-ray diffraction method. Polymer I crystallizes in the monoclinic system, space group C2/c with a=30.7515(6) A, b=10.9577(2) A, c=17.5545(4) A, β=112.040(1)°, V=5483.0(2) A3, Z=4, final R 1=0.0253 and wR 2=0.0606. In I, each Eu3+ ion is coordinated by four oxygen atoms from two carboxylate groups of two different Sip anions and five oxygen atoms from five coordinated water molecules to complete a deformed monocap square antiprism. Moreover, each Sip anion acts as a tetradentate ligand to connect two adjacent Eu3+ ions through its two chelating carboxylate groups, resulting in one-dimensional linear chains. In addition, fifteen different kinds of hydrogen-bonding interactions link the chains, lattice water molecules, and free Bipy molecules to engender a complicated hydrogen-bonding network.

Hydrothermal Syntheses and Structural Studies of Lanthanide Coordination Polymers Involving In‐Situ Decarboxylation and their Luminescence Properties

AbstractLanthanide coordination polymers with the formula [Ln(pydc)2]·H2O (Ln = La, 1; Nd, 2; pydc = 3,4‐pyridinedicarboxylate) and [Ln(pydc)(ina)(H2O)2] (Ln = Sm, 3; Eu, 4; Tb, 5; Dy, 6; pydc = 3,4‐pyridinedicarboxylate, ina = isonicotinate) were synthesized by treating LnIII nitrates with 3,4‐pyridinedicarboxylic acid under hydrothermal conditions. Single‐crystal and powder X‐ray diffraction studies indicate that these lanthanide coordination polymers adopt two different structures. The lighter lanthanide compounds 1 and 2 consist of extended two‐dimensional layer structures with the thickness of ca. 1.7 nm. While the heavier lanthanide compounds 3‐6 have pydc‐bridged double chain structures with one chelating carboxylate group of ina ligand and two water molecules on each metal center. Interestingly, decarboxylation occurred and pydc was partially transformed into ina in the hydrothermal reactions of 3‐6. The fluorescence activities of compounds 4 and 5 are reported.

Morphology of Zinc-Neutralized Maleated Ethylene−Propylene Copolymer Ionomers: Structure of Ionic Aggregates As Studied by X-ray Absorption Spectroscopy

X-ray absorption spectroscopy (EXAFS) was used to characterize zinc-neutralized ionomers made from ethylene−propylene copolymers with grafted maleic anhydride units (Zn-MAn-g-EPM). The structure of the zinc moieties in the dry system consisted of two chelating carboxylate groups around one zinc atoma structure much different than if the carboxylate anions come from acrylic or methacrylic acid. These self-contained zinc−two chelating carboxylate structures assemble into a larger superstructure as shown in a previous SAXS study, which indicated that the microphase-separated ionic aggregates are ∼2 nm. This superstructure must therefore contain significant amounts of nonionic material, consistent with the observation that the superstructure also forms in the unneutralized maleic anhydride precursor. After addition of water, zinc atoms in the sample with 10% of the carboxylate groups neutralized were fully solvated, i.e., zinc was surrounded by six water molecules. Zinc atoms in samples with higher neutraliza...

Crystallographic report: Bis[tri(o‐chlorobenzyl)tin(IV)] terephthalate

AbstractThe centrosymmetric structure of (o‐ClC6H4)3SnO2CC6H4CO2Sn(C6H4Cl‐o)3 features an unsymmetrically chelating carboxylate group, so that a distorted trigonal bipyramidal cis‐C3O2 coordination geometry for tin results. Copyright © 2004 John Wiley & Sons, Ltd.

Synthesis, structure and luminescent property of a binuclear terbium complex [Tb 2(Hsal) 8(H 2O) 2][(Hphen) 2]·2H 2O

A binuclear terbium complex [Tb 2(Hsal) 8(H 2O) 2][(Hphen) 2]·2H 2O 1 (Hsal= o-HOC 6H 4CO 2 −, phen=1,10-phenanthroline) was synthesized and characterized by elemental analysis, molar conductance, IR, UV–VIS, X-ray powder diffraction, Thermogravimetric analysis and fluorescence. Its structure was determined by X-ray single crystal diffraction. In the dimeric anion [Tb 2(Hsal) 8(H 2O) 2] 2−, two terbium atoms are connected by four bidentate bridging carboxylate groups. Each Tb atom is eight-coordinated to four bidentate bridging carboxylate groups, one bidentate chelating carboxylate groups, one monodentate carboxylate group as well as one water molecule. The mono-protonated phen does not coordinate to the Tb atom directly. Hydrogen bonds, π–π stacking interactions and electrostatic attractions result in the formation of a two-dimensional supramolecular structure. The solid-state luminescence behavior of 1 was studied. Compared with binary terbium salicylate Tb(Hsal) 3(H 2O) 2·2H 2O, it emits a relatively weak green light under the excitation of UV light, which may be attributed to the formation of extensive π-electron conjugation systems in the structure.

Synthesis, characterization, and crystal structures of three new divalent metal carboxylate-sulfonates with a layered and one-dimensional structure.

Hydrothermal reactions of 5-sulfoisophthalic acid (HO(3)SC(6)H(3)-1,3-(CO(2)H)(2), H(3)L) with M(II) carbonate (or oxide) and 4,4'-bipyridine (4,4'-bipy) (or 2,2'-bipyridine, 2,2'-bipy) resulted in three new metal carboxylate-sulfonate hybrids, namely, [CdL(H-4,4'-bipy)] (1) and [Cd(3)L(2)(2,2-bipy)(4)(H(2)O)(2)].2H(2)O (2) with layered structures and [ZnL(H-4,4'-bipy)(H(2)O)].2H(2)O (3), whose structure features a one-dimensional double chain. The cadmium(II) ion in complex 1 is seven-coordinated by five carboxylate oxygen atoms and one sulfonate oxygen atom from four ligands and a unidentate 4,4'-bipyridine. The interconnection of the cadmium(II) ions through bridging carboxylate-sulfonate ligands resulted in the formation of a <002> double layer with the bipyridyl rings orientated toward the interlayer space. Complex 2 has a different layered structure. Cd(1) is seven-coordinated by two bidentate chelating carboxylate groups from two ligands, a bidentate chelating 2,2'-bipy and an aqua ligand, and Cd(2) is octahedrally coordinated by two bidentate chelating 2,2'-bipy's, a sulfonate oxygen, and an aqua ligand. The coordination geometry around Cd(3) is similar to that of Cd(1) with the aqua ligand being replaced by an oxygen atom from the sulfonate group. The carboxylate-sulfonate ligand acts as pentadentate ligand, bridging with three cadmium(II) ions. The bridging of cadmium(II) ions through the carboxylate-sulfonate ligands resulted in the formation of <006> and <003> layers; the 2,2'-bipy molecules and [Cd(2)(2,2'-bipy)(2)(H(2)O)] cations are orientated to the interlayer space. Complex 3 features a 1D metal carboxylate-sulfonate double chain along the diagonal of the a- and b-axes. The zinc(II) ion is octahedrally coordinated by four carboxylate O atoms from three ligands, a unidentate 4,4'-bipy, and an aqua ligand. Each pair of zinc(II) ions is bridged by two carboxylate groups from two ligands to form a dimer, and such dimeric units are interconnected by bridging ligands to form a double chain. The sulfonate group of the carboxylate sulfonate ligand remains noncoordinated and forms a number of hydrogen bonds with aqua ligands as well as lattice water molecules.

Synthesis, structure and luminescence properties of europium and zinc ionic complexes

Two europium and zinc ionic complexes [Eu 2(Hsal) 8][Zn(phen) 3] · (H 2sal)(H 2O) ( 1) and [Eu 2(TPA) 8][Zn(TPA)(Phen) 2] 2 · (H 2O) 2 ( 2) (where H 2sal=salicylic acid, TPA=α-thiophene carboxylic acid, phen=1,10-phenanthroline) have been synthesized by the rheological phase reaction method and structurally characterized by IR spectra and X-ray crystallography. The results show that in both complexes the carboxylate groups adopt three modes: bidentate bridging, bidentate chelating and tridentate chelating-bridging. Complex 1 consists of a discrete dinuclear [Eu 2(Hsal) 8] 2− anion, [Zn(phen) 3] 2+ cation, free salicylic acid and a lattice water molecule. Interestingly, in the unit cell there are two types of dimeric [Eu 2(Hsal) 8] 2− anions with inversion centers. The hydrogen bonds between the chelating carboxylate groups and the lattice water molecules link the dimeric Eu1 units into 1-D chains. Complex 2 comprises of a dimeric [Eu 2(TPA) 8] 2− anion, two [Zn(TPA)(Phen) 2] + cations and two lattice water molecules. One obvious difference from complex 1 is that besides phen ligands, the TPA − group also coordinates to the Zn 2+ ion. The C–H⋯O, O–H⋯O hydrogen bonds and π–π stacking interactions play an important role in the crystal structure. These two complexes emit strong red light when irradiated by UV light. The emission bands at about 590, 610 nm correspond to the characteristic 5D 0 → 7F 1, 5D 0 → 7F 2 transitions of Eu 3+ ions. The large intensity ratio of 5D 0 → 7F 2/ 5D 0 → 7F 1 indicates the low symmetry of Eu 3+ ion sites in both complexes, consistent with the results of the structure determination.

Syntheses, characterizations and crystal structures of two new lead(II) amino and carboxylate–sulfonates with a layered and a pillared layered structure

Reactions of lead(II) acetate with m-aminobenzenesulfonic acid (H L 1) and 5-sulfoisophthalic acid (H 3 L 2) afforded two new lead(II) sulfonates, Pb( L 1) 2 1 and Pb 2( L 2)( μ 3-OH)(H 2O) 2. In compound 1, the lead(II) ion is eight-coordinated by two sulfonate groups bidentately, two sulfonate groups unidentately and two amino groups from six ligands. Each L 1 ligand is tetradentate and bridges with three Pb(II) ions. The interconnection of the Pb(II) ions via bridging sulfonate ligands resulted in 〈100〉 and 〈200〉 layers. In compound 2, one Pb(II) ion is six-coordinated by a carboxylate group bidentately, by two carboxylate groups unidentately, by a sulfonate oxygen atom and by an OH anion, whereas the other one is six-coordinated by a bidentate chelating carboxylate group, two μ 3-OH anions, a sulfonate oxygen atom and an aqua ligand. The interconnection of irregular PbO 6 polyhedra via carboxylate–sulfonate ligands resulted in the formation of a pillared layered structure with the 2D layer being formed; the lead(II) ions, hydroxyl groups, carboxylate and sulfonate groups and the benzene ring as the pillar agent.

Tetraaqua-1,2,4,5-benzenetetracarboxylato(pyrazine)dicobalt(II) dihydrate

The Co(II) atom in polymeric {[Co2(C10H2O8)(C4H4N2)(H2O)4]·2H2O}n exists in an octahedral coordination environment defined by the two O atoms of a chelating carboxyl group, the O atom of a monodentate carboxyl group of another benzene­tetra­carboxyl­ato unit, two water mol­ecules and the N atom of the pyrazine. The tetraanionic ligand and the N-heterocycle are located on inversion centers. The layer structure is linked by hydrogen bonds into a network structure.

Polymeric tetraaqua(1,2,4,5-benzenetetracarboxylato)(pyrazine)dinickel(II) dihydrate

The Ni atom in the title compound, {[Ni2(C10H2O8)(C4H4N2)(H2O)4]·2H2O}n, exists in an octahedral NO5Ni coordination environment that is defined by the two O atoms of a chelating carboxyl group, the O atom of a monodentate carboxyl group belonging to another carboxy­lato tetraanion, two water mol­ecules and the N atom of the N-heterocycle. The tetra­carboxyl­ato anion and the pyrazine mol­ecule are each located on a center of inversion. The bonding pattern leads to the formation of a layer structure; the layers are linked into a three-dimensional network by extensive hydrogen bonds involving the water mol­ecules and the O atoms of the anionic unit.

Synthesis and characterization of di‐n‐butyltin(IV) complexes with 4′/2′‐nitrobiphenyl‐2‐carboxylic acids: X‐ray crystal structures of [{(n‐C4H9)2Sn(OCOC12H8NO2−4′)}2O]2 and (n‐C4H9)2Sn{OCOC12H8NO2−4′}2

AbstractReactions of di‐n‐butyltin(IV) oxide with 4′/2′‐nitrobiphenyl‐2‐carboxylic acids in 1 : 1 and 1 : 2 stoichiometry yield complexes [{(n‐C4H9)2Sn(OCOC12H8NO2−4′/2′)}2O]2 (1 and 2) and (n‐C4H9)2Sn(OCOC12H8NO2−4′/2′)2 (3 and 4) respectively. These compounds were characterized by elemental analysis, IR and NMR (1H, 13C and 119Sn) spectroscopy. The IR spectra of these compounds indicate the presence of anisobidentate carboxylate groups and non‐linear CSnC bonds. From the chemical shifts δ (119Sn) and the coupling constants 1J(13C, 119Sn), the coordination number of the tin atom and the geometry of its coordination sphere have been suggested. [{(n‐C4H9)2Sn(OCOC12H8NO2−4′)}2O]2 (1) exhibits a dimeric structure containing distannoxane units with two types of tin atom with essentially identical geometry. To a first approximation, the tin atoms appear to be pentacoordinated with distorted trigonal bipyramidal geometry. However, each type of tin atom is further subjected to a sixth weaker interaction and may be described as having a capped trigonal bipyramidal structure. The diffraction study of the complex (n‐C4H9)2Sn(OCOC12H8NO2−4′)2 (3) shows a six–coordinate tin in a distorted octahedral frame containing bidentate asymmetric chelating carboxylate groups, with the n‐Bu groups trans to each other. The n‐BuSnn‐Bu angle is 152.8° and the SnO distances are 2.108(4) and 2.493(5) Å. The oxygen atom of the nitro group of the ligand does not participate in bonding to the tin atom in 1 and 3. Crystals of 1 are triclinic with space group P1 and of that of 3 have orthorhombic space group Pnna. Copyright © 2003 John Wiley &amp; Sons, Ltd.

Crystal Structures and Thermal Behaviour of Lanthanide(III) Hexanoate 1, 10‐Phenanthroline Complexes, [M(C5H11CO2)3(phen)] and [Tm(C5H11CO2)2(NO3)(phen)

AbstractLanthanide(III) hexanoate 1, 10‐phenanthroline complexes crystallise in the space group P21/n. The compounds consist of dimers, whereby two lanthanide ions are held together by two bidentate bridging and two tridentate bridging carboxylate groups. The first coordination sphere of the lanthanide ions is completed by one bidentate chelating carboxylate group and by one bidentate 1, 10‐phenanthroline molecule, resulting in the coordination number 9. The dimers have a spherical form, which has important consequences for the thermal properties of complexes. The basic idea behind the preparation of this type of compounds is the stabilisation of the ionic lanthanide layer, so that the smaller lanthanide ions (from which the normal alkanoates do not show mesomorphism because they are too small) show liquid crystallinity. The stabilisation of the ionic layer was successful, expressed by the high melting temperatures, but mesomorphism is not observed. The absence of mesomorphism is related to the isotropic structure of the compounds. A lower symmetry is obtained when a hexanoate group is replaced by a nitrate group. Thulium(III) dihexanoate nitrate 1, 10‐phenanthroline crystallises in the space group P1¯. However, this compound also shows a spherical dimeric structure, but no mesomorphism.

Carboxylate versus imidobenzoate bonding for anthranilic acid derivatives. Crystal structures of [W( η-C 5Me 5)Cl 3( η2-O 2CC 6H 4NH 2-2)] and [ReCl(OEt)(PPh 3) 2(NC 6H 4CO 2)

The paramagnetic complex [W( η-C 5Me 5)Cl 3( η 2-O 2CC 6H 4NH 2-2)] ( 1) has been obtained by reaction of [W( η-C 5Me 5)Cl 4] with anthranilic acid [1,2-(NH 2)(CO 2H)C 6H 4]; the X-ray crystal structure shows a pseudo-octahedral geometry with a mer arrangement of chlorines and a symmetrically chelating carboxylate group containing a pendant non-coordinated NH 2 group. Contrastingly, [ReCl(OEt)(PPh 3) 2(NC 6H 4CO 2)] ( 2), the product of the reaction between [ReOCl 3(PPh 3) 2] and anthranilic acid contains pseudo-octahedral rhenium with a chelating imidobenzoate ligand and trans-phosphines which are mutually cis to the bent imido function [Re–N(1)–C(1)=143.5(3)°]. The carboxylate group of the chelating ligand is trans to a chloride with the remaining site ( trans to the imido function) occupied by an ethoxide ligand.

Luminescent Lanthanide Coordination Polymers

One-dimensional lanthanide coordination polymers with the formula Ln(isonicotinate)3(H2O)2 (Ln = Ce, Pr, Nd, Sm, Eu, Tb; 1a−f) were synthesized by treating nitrate or perchlorate salts of Ln(III) with 4-pyridinecarboxaldehyde under hydro(solvo)thermal conditions. Single-crystal and powder X-ray diffraction studies indicate that these lanthanide coordination polymers adopt two different structures. While Ce(III), Pr(III), and Nd(III) complexes adopt a chain structure with alternating Ln−(carboxylate)2−Ln and Ln−(carboxylate)4−Ln linkages, Sm(III), Eu(III), and Tb(III) complexes have a doubly carboxylate-bridged infinite-chain structure with one chelating carboxylate group on each metal center. In both structures, the lanthanide centers also bind to two water molecules to yield an eight-coordinate, square antiprismatic geometry. The pyridine nitrogen atoms of the isonicotinate groups do not coordinate to the metal centers in these lanthanide(III) complexes; instead, they direct the formation of Ln(III) coor...

Catena-Poly[[diaqua(3-cyanobenzoato-O,O')erbium]-bis-μ-(3-cyanobenzoato-O:O')

The title compound, [Er(C 8 H 4 NO 2 ) 3 (H 2 O) 2 ] n , has a one-dimensional chain structure bridged by carboxylate groups. The Er III atom and one 3-cyanobenzoate ligand lie on a twofold axis and this ligand has its cyano group disordered over two sites. Each Er III atom is surrounded by two O atoms from one chelating carboxylate group, four O atoms from four different bridging carboxylate groups and two water molecules, leading to a square-antiprism coordination polyhedron.

Synthesis and structural characterization of a novel polymeric praseodymium(III) complex with a new flexible double betaine

A novel polymeric Pr(III) complex with a new double betaine, namely [{Pr(L-1)(1.5)(H2O)(2)}(n)] [ClOli4]3(n). nH(2)O (1) (L-1= 1,4-diazoniobicyclo[2,2,2]octane- 1,4-dipropionate), has been synthesized and characterized by X-ray analysis. In the title complex, the Pr(III) atom is nine-coordinated by seven oxygen atoms from five L-1 ligands and two aqua ligands. Each pair of adjacent praseodymium(III) atoms is linked by a pair of mu(3) chelating and bridging carboxylate groups, thus forming an infinite metal metal chain running parallel to the a direction, and such chains are cross-linked by flexible backbones of L-1 ligands into a three-dimensional network with the perchlorate anions and lattice water molecules accommodated in the interstitial space. The title complex crystallizes in the monoclinic space group P2(1)/n with a = 8.085(2), b = 14.316(3), c = 29.775(6) Angstrom, beta = 103.04(3)degrees and Z = 4.

Synthesis and structural characterization of a novel polymeric gadolinium(III)–copper(II) complex of iminodiacetic acid

A novel polymeric Gd2Cu3 complex of iminodiacetic acid (H2L1=NH{CH2COOH}2), namely, Gd2Cu3(L1)6, 1, has been synthesized and structurally characterized. In the title complex, the Gd3+ ion is nine-coordinated by six O atoms from three bidentate chelating carboxylate groups and three O atoms from three anti-anti bridging carboxylic groups of six L1 ligands; the Cu2+ ion is six-coordinated by four O and two N atoms from two chelating L1 ligands. Each pair of Gd(III) atoms is bridged by three L1 ligands, each of which also chelates with one copper(II) ion, thus forming a Gd2Cu3 cluster unit. Such cluster units are cross-linked by flexible L1 ligands into a three-dimensional coordination framework. The title complex crystallizes in the trigonal space group P-3c1 (No. 165) with a = b = 13.433(4), c = 14.770(6) A; V = 2308(1) A3; Dcalca = 1.859 g cm−3; Z = 2.

Organometallic Complexes with Biological Molecules: VIII. Synthesis, Solid State andin vivo Investigation of Triorganotin(IV) Derivatives ofL-Homocysteic Acid

Several new triorganotin(IV) derivatives of L-homocysteic acid (L-HCAH) with formula R3Sn(L-HCA) (R=Me, nBu, Ph) have been synthesized. Their solid-state configurations were determined by IR and Mössbauer spectroscopy. The tin(IV) atom is five-coordinated in all the complexes, with the L-homocysteic acid behaving as a monoanionic bidentate ligand coordinating the tin(IV) atom through a chelating or bridging carboxylate group. The sulfonate (SO3−) and NH3+ groups of L-homocysteic acid maintain their free acid configuration and hence do not participate to the coordination of the tin(IV) atom. Coordination hypotheses have been checked through the correlation between the Mössbauer parameter isomer shift, δ, and partial atomic charge on the tin atoms, QSn, performed, for all the new organotin(IV) compounds, on the basis of an equalization procedure applied to idealized trigonal-bipyramidal structures for R3Sn(L-HCA). 1H and 13C NMR spectra of the complexes show that pentacoordination of the tin atom, with R groups in the equatorial plane of a trigonal bipyramid, is retained in DMSO solution. The NMR data confirm also that the uncoordinated NH3+ group of the ligand is still present in solution. Results gathered after exposure of two- to four-cell embryos of the sea urchin Paracentrotus lividus (Echinodermata) to the triorganotin(IV) L-homocysteate derivatives as well as to the parent triorganotin(IV) chlorides document cytotoxicity of the complexes, while free L-homocysteic acid exerts no significant toxic activity. The trimethyltin(IV) L-homocysteate derivative seems to exert a lower cytotoxicity than the tributyl- and triphenyl-tin(IV) ones. Different structural lesions have been identified by comparative analysis of mitotic chromosomes from untreated embryos (negative controls) and embryos treated with triorganotin(IV) L-homocysteate derivatives, such as (1) suppression of the stretch among sister chromatids at the beginning of anaphase stage; (2) deeply stained zones mainly located at the telomeric regions of chromosomes; (3) arm breakages; and (4) chromosome bridges among daughter chromosomes at anaphase stage. A colchicine-like effect of triorganotin(IV) L-homocysteate derivatives was observed. © 1997 John Wiley & Sons, Ltd.

Differentiating Between Monodentate and Bidentate Carboxylate Ligands Coordinated to Uranyl Ions Using EXAFS

We have investigated the U L III -edge EXAFS of two carboxylato uranyl complexes of known structure to explore the possibilty of differentiating between monodentate and bidentate coordinated carboxylate ions. The interpretation of EXAFS results from uranyl complexes with carboxylate ions based solely on axial and equatorial bond lengths can be inconclusive; information from further-distant shells is often needed. Multiple scattering (MS) pathways along the O=U=O unit and in coordinating chelating or monodentate carboxylate groups can make substantial contributions to the EXAFS. Therefore, MS pathways were calculated using FEFF6 [1] and considered in the data analysis. EXAFS results are compared to XRD data reported in the literature.