In this study, smelter contaminated soil was treated with various soil amendments (ferric sulphate [Fe2(SO4)3], triple superphosphate [TSP] and biochar) to determine their efficacy in immobilizing soil lead (Pb) and arsenic (As). XAS were collected on soils and mine waste materials at the Materials Research Collaborative Access Team 10-BM for As and 10-ID for Pb, Advanced Photon Source at Argonne National Laboratory. Arsenic XAS data collection at 10-BM was measured at the As K edge (11867 eV) using a 4-element Vortex fluorescence detector. Four layers of aluminum foil to filter out background fluorescence from iron and other elements in the samples. Three to five step scans were collected in fluorescence by Vortex detector at 45° incident to sample and down beam transmission on energy calibration standard. Energy was calibrated to set at the 1st derivative inflection point zero of sodium arsenate standard to 11874 eV. Data were then background subtracted and converted to k space for EXAFS region analysis. Data processed for EXAFS analysis were k3-weighted and all e0 set to 11870 eV for uniform k range start energy. Spline range was 0.5-12 k. Lead XAS data collection at 10-ID utilized a Si(111) mono to tune energy to the Pb L3-edge (13035 eV). Samples were measured in fluorescence using a Mirion-Canberra 7-element Ge detector at 45° incident to the sample. For each sample, three to five scans were collected in both transmission and fluorescence mode with a Pb foil for reference sample. Calibration was performed by assigning the first derivative inflection point of Pb foil scan to 13035 eV. Analysis of Pb spectra utilized LCF of the 1st derivative norm(E) from -20 to 80 eV from e0, constraints of all weights between 0 and 1 and sum of weights normalized to 1. Standards were sequentially removed based on statistical improvement of fit. Components contributing less than ten percent were removed, followed by refitting with remaining components. The combination of standards resulting in the lowest R-factor results for each sample was reported. Arsenic spectra were analyzed LCF utilizing the EXAFS range of spectra. Preliminary data checking indicated As oxidation states of all samples contained only AsV as confirmed by matching edge position with the sodium arsenate pellet used for energy calibration. As EXAFS range were utilized for quantitative speciation from a k-range of 3-10 Å-1. This dataset is associated with the following publication: Alankarage, D., A. Betts, K.G. Scheckel, C. Herde, M. Cavallaro, and A.L. Juhasz. Remediation options to reduce bioaccessible and bioavailable lead and arsenic at a smelter impacted site - consideration of treatment efficacy. ENVIRONMENTAL POLLUTION. Elsevier Science Ltd, New York, NY, USA, 341: 122881, (2024).

K-space EXAFS spectra; additional PXRD results; EXAFS fitting for reference t-ZrO2; fwhm analysis of first derivative of the Zr K-edge XANES main edge; EXAFS fitting for reference h-ZnO; test Zr K-edge EXAFS fitting of ZrZn-5 using a c-ZrO2 model; additional details on input structures employed in Zn K-edge EXAFS fitting; additional details on cluster size evaluation; additional details on in situ XAS data during activation in H2 and related EXAFS analysis using the Einstein model; in situ XAS data under reaction conditions (CO2/H2, 300 °C, 15 bar)

The results for 3.12 and 5.06 mol∙kg-1 NiCl2 solutions using X-ray diffraction [21,25] are also listed. The concentrations are expressed in molality (mol∙kg-1). Uncertainty limits are given in parentheses.a Value fixed (not optimized) during refinements.b Sum of number of O and Cl fixed to be equal to 6.c Solid standard.d Concentration in molarity (mol∙L-1) in references [21,25], converted to molality (mol∙kg-1).Results of Ni EXAFS analysis of the Ni(II) first shell structure under ambient conditions.

EXAFS simulation parametersa.

Human serum albumin (HSA) is involved physiologically in heme scavenging; in turn, heme-albumin (HSA-heme-Fe) displays globin-like properties. Here, the allosteric effect of ibuprofen and warfarin on the local atomic structure around the ferric heme-Fe (heme-Fe(III)) atom of HSA-heme-Fe (HSA-heme-Fe(III)) has been probed by Fe-K edge X-ray absorption spectroscopy (XAS). The quantitative analysis of the Fe-K edge extended X-ray absorption fine structure (EXAFS) signals and modeling of the near edge (XANES) spectral features demonstrated that warfarin and ibuprofen binding modify the local structure of the heme-Fe(III). Combined XAS data analysis and targeted molecular dynamics (MD) simulations provided atomic resolution insights of protein structural rearrangements required to accommodate the heme-Fe(III) upon ibuprofen and warfarin binding. In the absence of drugs, the heme-Fe(III) atom is penta-coordinated having distorted 4+1 configuration made by the nitrogen atoms of the porphyrin ring and the oxygen phenoxy atom of the Tyr161 residue. MD simulations show that ibuprofen and warfarin association to the secondary fatty acid (FA) binding site 2 (FA2) induces a reorientation of domain I of HSA-heme-Fe(III), this leads to the redirection of the His146 residue providing an additional bond to the heme-Fe(III) atom, providing the 5+1 configuration. The comparison of Fe-K edge XANES spectra calculated using MD structures with those obtained experimentally confirms the reliability of the proposed structural model. As a whole, combining XAS and MD simulations it has been possible to provide a reliable model of the heme-Fe(III) atom coordination state and to understand the complex allosteric transition occurring in HSA-heme-Fe(III) upon ibuprofen and warfarin binding.

In order to establish structure–reactivity relationships in propylene metathesis as a function of the podality of tungsten oxo species bearing neosilyl ligands, we targeted the parent tris alkyl [(SiO)WOR3] and bis alkyl oxo [(SiO)2WOR2] derivatives prone to carbene formation. Thus, WO(CH2SiMe3)3Cl was grafted onto silica dehydroxylated at 700 °C (SiO2–700), proceeding via W–Cl cleavage to yield well-defined monopodal species (SiO)WO(CH2SiMe3)3 along with HCl release. On the other hand, the corresponding bipodal species (SiO)2WO(CH2SiMe3)2 was obtained on SiO2–200 by release of both HCl and TMS. The formation of these species were demonstrated by mass balance analysis, elemental analysis, IR, advanced solid-state NMR (1D and 2D 1H, 13C, 29Si, and 17O), and EXAFS. Furthermore, DFT calculations allowed understanding and rationalizing the experimental results regarding grafting selectivity. Materials 2a and 2b proved to lead to stable and efficient supported tungsten oxo catalysts for propene metathesis under dynamic conditions at 80 °C. The symmetric bipodal precatalyst (expressed as W(E)(CHR)(X)(Y)) showed somewhat higher activity than the asymmetric (X ≠ Y) counterparts.

Mechanistic studies through Ti K-edge XANES and EXAFS spectra of the catalyst solution for 1-hexene polymerization using Cp*TiX2(O-2,6-iPr2C6H3) [X = Cl (1), Me (2)]–MAO catalysts and for syndiospecific styrene polymerization using (tBuC5H4)TiCl2(O-2,6-iPr2C6H3) (3)–MAO catalyst have been explored. Significant changes in the XANES spectrum (low energy shift in the edge peak, in addition to decrease in intensities of two pre-edge peaks) were observed when styrene (200 equiv) was added into a toluene solution containing 3 and MAO, strongly suggesting that the complex 3 [Ti(IV)] was reduced to Ti(III) by addition of styrene under these conditions. The EXAFS analysis suggests that the Ti–O bond (corresponding to coordination of phenoxide) was preserved along with dissociation of Ti–Cl bonds by treating with MAO. These XAS analysis data thus suggest that neutral Ti(III) species, (tBuC5H4)Ti(R)(OAr), play a role as the active species. The DFT-based computational analysis on the syndiospecific styrene insertion reaction also revealed that the neutral Ti(III) catalyst exhibits the lower activation energy than the others, strongly supporting the above mechanism. In contrast, no significant changes (in the oxidation state, basic structure) in the XANES spectra were observed when the toluene solution containing 1 (or 2) was added MAO and 1-hexene, whereas preservation of the Ti–O bond along with dissociation of the Ti–Cl by treating with MAO was suggested through the EXAFS analysis.

Calcium tungstate (CaWO4) crystals were prepared by microwave-assisted hydrothermal (MAH) and polymeric precursor methods (PPM). These crystals were structurally characterized by X-ray diffraction (XRD), N2 adsorption, X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) measurements. The morphology and size of these crystals were observed by field emission scanning electron microscopy (FE-SEM). Their optical properties were investigated by ultraviolet visible (UV-Vis) absorption and photoluminescence (PL) measurements. Moreover, these materials were employed as catalysts towards gas phase toluene oxidation reaction. XRD indicates the purity of materials for both preparation methods and MAH process produced crystalline powders synthesized at lower temperatures and shorter processing time compared to the ones prepared by PPM. FE-SEM images showed particles with rounded morphology and particles in clusters dumbbells-like shaped. PL spectra exhibit a broad band covering the visible electromagnetic spectrum in the range of 360 to 750 nm. XANES and EXAFS results show that preparation method does not introduce high disorders into the structure, however the H2-TPR results indicated that the catalyst reducibility is affected by the preparation method of the samples.

(Arylimido)vanadium(V) dichloride complexes containing anionic N-heterocyclic carbene (NHC) ligands that contain weakly coordinating B(C6F5)3 moieties (WCA-NHC) of the type V(NAr)Cl2(WCA-NHC-Ar′) showed significant catalytic activity for ethylene polymerization in the presence of Al cocatalysts (MAO and AliBu3); the activity by the 5–MAO catalyst (19 500 kg-PE/mol-V·h; TOF 11 600 min–1) is the highest among those reported using the other (imido)vanadium(V) complexes in the presence of MAO, and the 5–AliBu3 catalyst showed higher activity (66 000 kg-PE/mol-V·h; TOF 39 200 min–1). The V K-edge X-ray absorption near-edge structure (XANES) analyses (in toluene) strongly suggest the formation of certain vanadium(III) species by reduction with AliBu3 accompanying structural changes; the EXAFS analysis suggests the presence of the arylimido ligand and one V–Cl bond (2.34 ± 0.04 Å), which is longer than those [2.1901(8)–2.2462(8) Å] in the reported (imido)vanadium(V) complexes. The XANES analysis of [V(NAr)Cl2(OAr)] strongly suggests the formation of the other vanadium(III) species by reduction with Me2AlCl or Et2AlCl, and the EXAFS analysis suggests the presence of the arylimido ligand and two V–Cl bonds (2.45 ± 0.03 Å). The XANES spectra showed no significant changes in both the pre-edge peak(s) and the edge peak when these complexes were treated with MAO, suggesting that the basic geometry and the high oxidation state were preserved under these conditions.

The crystal structures of the complexes formed by reaction of thorium(IV) nitrate with iminodiacetic acid (H2IDA), nitrilotriacetic acid (H3NTA), and ethylenediaminetetraacetic acid (H4EDTA) under hydrothermal conditions are reported. In [Th(HIDA)2(C2O4)]·H2O (1), the metal atom is chelated by two carboxylate groups from two HIDA− anions and by two oxalate ligands formed in situ; two additional oxygen atoms from two more HIDA− anions complete the ten-coordinate environment of bicapped square antiprismatic geometry. The uncoordinated nitrogen atom is protonated and involved in hydrogen bonding. Two different ligands are present in [Th(NTA)(H2NTA)(H2O)]·H2O (2), one of them being a O3,N-chelating trianion which acts also as a bridge toward two neighboring metal ions, and the other being a bis-monodentate bridging species with an uncoordinated carboxylic arm and a central ammonium group. An aqua ligand completes the nine-coordinated, capped square antiprismatic metal environment. The EDTA4− anion in [Th(EDTA)(H2O)]·2H2O (3) is chelating through one oxygen atom from each carboxylate group and the two nitrogen atoms, as in a previously reported molecular complex. Two carboxylate groups are bridging, which, with the addition of an aqua ligand, gives a capped square antiprismatic coordination polyhedron. Aminopolycarboxylate ligands have been much investigated in relation with actinide decorporation and nuclear wastes management studies, and the present results add to the structural information available on their complexes with thorium(IV), which has mainly been obtained up to now by extended X-ray absorption fine structure (EXAFS) spectroscopy. In particular, the bridging (non-chelating) coordination mode of H2NTA− is a novel feature in this context. All three complexes crystallize as two-dimensional assemblies and are thus novel examples of thorium−organic coordination polymers.

Treatment of FeIV(O)(TPA)(NCMe)2 [TPA, N,N,N-tris(2-pyridylmethyl)amine] with 3 equiv of NR4X (X = CF3CO2, Cl, or Br) in MeCN at −40 °C affords a series of metastable [FeIV(O)(TPA)(X)]+ complexes. Some characteristic features of the S = 1 oxoiron(IV) unit are quite insensitive to the ligand substitution in the equatorial plane, namely, the Fe−O distances (1.65−1.66 Å), the energy (∼7114.5 eV) and intensity [25(2) units] of the 1s-to-3d transition in the X-ray absorption spectra, and the Mössbauer isomer shifts (0.01−0.06 mm·s-1) and quadrupole splittings (0.92−0.95 mm·s-1). The coordination of the anionic X ligand, however, is evidenced by red shifts of the characteristic near-IR ligand-field bands (720−800 nm) and spectroscopic observation of the bound anion by 19F NMR for X = CF3CO2 and by EXAFS analysis for X = Cl (rFe-Cl = 2.29 Å) and Br (rFe-Br = 2.43 Å). Density functional theory calculations yield Mössbauer parameters and bond lengths in good agreement with the experimental data and produce excited-state energies that follow the trend observed in the ligand-field bands. Despite mitigating the high effective charge of the iron(IV) center, the substitution of the MeCN ligand with monoanionic ligands X- decreases the thermal stability of [FeIV(O)(TPA)]2+ complexes. These anion-substituted complexes model the cis−X−FeIVO units proposed in the mechanisms of oxygen-activating nonheme iron enzymes.