57 results on '"Benjamin W. Stein"'
Search Results
2. Spectroscopic and electrochemical characterization of a Pr4+ imidophosphorane complex and the redox chemistry of Nd3+ and Dy3+ complexes
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Natalie T. Rice, Ivan A. Popov, Rebecca K. Carlson, Samuel M. Greer, Andrew C. Boggiano, Benjamin W. Stein, John Bacsa, Enrique R. Batista, Ping Yang, and Henry S. La Pierre
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Inorganic Chemistry - Abstract
Tetravalent praseodymium in a homoleptic imidophosphorane complex is identified and characterized in solution via UV-vis-NIR, cyclic voltammetry, theoretical calculations, and X-band EPR.
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- 2022
3. Whispering gallery mode resonators in continuous flow: spectral assignments and sensing with monodisperse microspheres
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Bryan C. Paulus, Jenny K. Banh, Kirk D. Rector, Benjamin W. Stein, and Laura M. Lilley
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Refractometry ,General Chemical Engineering ,General Engineering ,Microspheres ,Analytical Chemistry - Abstract
Whispering gallery mode resonator (WGMR) microspheres yield highly structured optical spectra that are extremely sensitive to their environment and are of intense interest for use in a variety of sensing applications. Many efforts to leverage the unique sensitivities of WGMRs have relied on stringent experimental requirements to correlate specific spectral shifts/changes to an analyte/stimulus such as (1) precise positional knowledge, (2) reference spectra for each microsphere, and (3) high mechanical stability. Consequently, these factors can hinder adequate mixing or incorporation of analytes and can create challenges for remote sensing. This work describes a continuous flow technique for measuring whispering gallery mode (WGM) spectra of dye-doped microspheres suspended in solution and an accompanying analysis scheme that can extract the local refractive index without
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- 2022
4. Understanding the Photochemical Properties of Polythiophene Polyelectrolyte Soft Aggregates with Sodium Dodecyl Sulfate for Antimicrobial Activity
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Benjamin W. Stein, Mohammed I Khalil, Maksim Y. Livshits, Eva Y. Chi, Dylan M. Brown, Samuel M. Greer, Andrea Scheberl, Erik Reimhult, Edward W. Strach, David G. Whitten, Fahimeh Maghsoodi, Jeffrey J. Rack, and Jianzhong Yang
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Materials science ,Polymers ,Surface Properties ,Microbial Sensitivity Tests ,Thiophenes ,medicine.disease_cause ,Photochemistry ,chemistry.chemical_compound ,Escherichia coli ,medicine ,General Materials Science ,Reactivity (chemistry) ,Particle Size ,Sodium dodecyl sulfate ,chemistry.chemical_classification ,Molecular Structure ,Cationic polymerization ,Sodium Dodecyl Sulfate ,Polymer ,Photochemical Processes ,Polyelectrolytes ,Polyelectrolyte ,Anti-Bacterial Agents ,chemistry ,Critical micelle concentration ,Polythiophene ,Reactive Oxygen Species - Abstract
The threat of antibiotic-resistant bacteria is an ever-increasing problem in public health. In this report, we examine the photochemical properties with a proof-of-principle biocidal assay for a novel series of regio-regular imidazolium derivative poly-(3-hexylthiophene)/sodium dodecyl sulfate (P3HT-Im/SDS) materials from ultrafast sub-ps dynamics to μs generation of reactive oxygen species (ROS) and 30 min biocidal reactivity with Escherichia coli (E. coli). This broad series encompassing pure P3HT-Im to cationic, neutral, and anionic P3HT-Im/SDS materials are all interrogated by a variety of techniques to characterize the physical material structure, electronic structure, and antimicrobial activity. Our results show that SDS complexation with P3HT-Im results in aggregate materials with reduced ROS generation and light-induced anti-microbial activity. However, our characterization reveals that the presence of non-aggregated or lightly SDS-covered polymer segments is still capable of ROS generation. Full encapsulation of the P3HT-Im polymer completely deactivates the light killing pathway. High SDS concentrations, near and above critical micelle concentration, further deactivate all anti-microbial activity (light and dark) even though the P3HT-Im regains its electronic properties to generate ROS.
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- 2021
5. Characterizing Extraction Chromatography for Large-Scale Americium-241 Processing
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Stosh A. Kozimor, Sara L. Thiemann, Daniel L. Huber, Benjamin W. Stein, David Dan, Mila Nhu Lam, David B. Kimball, Sara L. Adelman, Veronika Mocko, Jenifer C. Shafer, and Brian T. Arko
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Chromatography ,Scale (ratio) ,Chemistry ,General Chemical Engineering ,Extraction (chemistry) ,chemistry.chemical_element ,Americium ,General Chemistry ,Industrial and Manufacturing Engineering - Published
- 2021
6. Hyperspectral X-Ray Imaging: Progress Towards Chemical Analysis in the SEM
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Ping Yang, Katrina Koehler, Eric G. Bowes, Enrique R. Batista, Gene C. Hilton, M. H. Carpenter, Carl D. Reintsema, Douglas A. Bennett, Daikang Yan, Johnathon D. Gard, Zachary K. Baker, Daniel S. Swetz, Michael W. Rabin, M. P. Croce, Katherine A. Schreiber, Gregory L. Wagner, Joel C. Weber, Daniel T. Becker, Daniel Schmidt, Benjamin W. Stein, Chandler M. Smith, Christopher J. Fontes, Galen C. O'Neil, Abigail L. Wessels, Joel N. Ullom, Matthew L. Handley, J. Imrek, Kelsey M. Morgan, John A. B. Mates, and Daniel G. McNeel
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Cryostat ,Materials science ,Pixel ,Scanning electron microscope ,business.industry ,Detector ,Hyperspectral imaging ,Condensed Matter Physics ,01 natural sciences ,Sample (graphics) ,Electronic, Optical and Magnetic Materials ,Chemical species ,Optics ,0103 physical sciences ,Electrical and Electronic Engineering ,010306 general physics ,business ,Microwave - Abstract
The Hyperspectral X-ray Imaging (HXI) project will enable non-destructive chemical-state determination of nano-scale samples in the electron microscope for nuclear safeguards applications. To efficiently measure chemical state through electron-excited X-ray emission requires a combination of wide spectral bandwidth, high resolution, and high count rate capability. We are building a next-generation X-ray detector based on an array of transition edge sensors (TESs) to make these measurements possible and routine in the scanning electron microscope (SEM). Leveraging the large pixel densities afforded by microwave multiplexing readout and continuous, uninterrupted operation of a cryogen-free dilution refrigerator, this instrument will have efficiency to allow chemical species identification of nano-scale samples in hours instead of days to weeks. We describe prototype pixel designs for this HXI instrument, comprising three pixel types that will make up the hybrid TES array. Engineering design of the integrated HXI cryostat and SEM system is in progress, with full detector commissioning expected in Spring 2021 followed closely by full-scale integration with the SEM. We also report on the commissioning of a complementary TES-based X-ray emission spectroscopy platform for bulk samples to build a spectral library for HXI sample identification.
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- 2021
7. Photochemical separation of plutonium from uranium
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Ida M. DiMucci, Harrison D. Root, Zachary R. Jones, Stosh A. Kozimor, Molly M. MacInnes, Jeffrey L. Miller, Veronika Mocko, Warren J. Oldham, and Benjamin W. Stein
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Materials Chemistry ,Metals and Alloys ,Ceramics and Composites ,General Chemistry ,Catalysis ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials - Abstract
Plutonium-based technologies would benefit if chemical hazards for purifying plutonium were reduced. One critical processing step where improvements could be impactful is the adjustment of plutonium oxidation-states during separations. This transformation often requires addition of redox agents. Unfortunately, many of the redox agents used previously cannot be used today because their properties are deemed incompatible with modern day processing facilities and waste stream safety requirements. We demonstrated herein that photochemistry can be used as an alternative to those chemical agents. We observed that (1) Pu
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- 2022
8. Oxidizing Americium(III) with Sodium Bismuthate in Acidic Aqueous Solutions
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Natalie T. Rice, Elodie Dalodière, Sara L. Adelman, Zachary R. Jones, Stosh A. Kozimor, Veronika Mocko, Harrison D. Root, and Benjamin W. Stein
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Inorganic Chemistry ,Physical and Theoretical Chemistry - Abstract
Historic perspectives describing f-elements as being redox "inactive" are fading. Researchers continue to discover new oxidation states that are not as inaccessible as once assumed for actinides and lanthanides. Inspired by those contributions, we studied americium(III) oxidation in aqueous media under air using NaBiO
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- 2022
9. High Resolution X-Ray Spectra for Chemical Speciation in the SEM
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Eric G. Bowes, Lei Xu, Chandler M. Smith, Michael W. Rabin, Enrique R. Batista, Benjamin W. Stein, M. P. Croce, Katherine A. Schreiber, M. H. Carpenter, Christopher J. Fontes, Katrina Koehler, Daniel G. McNeel, Gregory L. Wagner, and Ping Yang
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Materials science ,Chemical speciation ,Analytical chemistry ,High resolution ,Instrumentation ,X ray spectra - Published
- 2021
10. High-Frequency and -Field Electron Paramagnetic Resonance Spectroscopic Analysis of Metal–Ligand Covalency in a 4f7 Valence Series (Eu2+, Gd3+, and Tb4+)
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Samuel M. Greer, Ningxin Jiang, Thaige P. Gompa, Benjamin W. Stein, Andrew Ozarowski, Natalie T. Rice, Henry S. La Pierre, and Joshua Telser
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Lanthanide ,Valence (chemistry) ,Coordination sphere ,010405 organic chemistry ,Chemistry ,chemistry.chemical_element ,Terbium ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,law.invention ,Inorganic Chemistry ,Crystallography ,law ,Oxidation state ,Excited state ,Physical and Theoretical Chemistry ,Electron paramagnetic resonance ,Ground state - Abstract
The recent isolation of molecular tetravalent lanthanide complexes has enabled renewed exploration of the effect of oxidation state on the single-ion properties of the lanthanide ions. Despite the isotropic nature of the 8S ground state in a tetravalent terbium complex, [Tb(NP(1,2-bis-tBu-diamidoethane)(NEt2))4], preliminary X-band electron paramagnetic resonance (EPR) measurements on tetravalent terbium complexes show rich spectra with broad resonances. The complexity of these spectra highlights the limits of conventional X-band EPR for even qualitative determination of zero-field splitting (ZFS) in these complexes. Therefore, we report the synthesis and characterization of a novel valence series of 4f7 molecular complexes spanning three oxidation states (Eu2+, Gd3+, and Tb4+) featuring a weak-field imidophosphorane ligand system, and employ high-frequency and -field electron paramagnetic resonance (HFEPR) to obtain quantitative values for ZFS across this valence series. The series was designed to minimize deviation in the first coordination sphere from the pseudotetrahedral geometry in order to directly interrogate the role of metal identity and charge on the complexes' electronic structures. These HFEPR studies are supported by crystallographic analysis and quantum-chemical calculations to assess the relative covalent interactions in each member of this valence series and the effect of the oxidation state on the splitting of the ground state and first excited state.
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- 2021
11. Advancing the Am Extractant Design through the Interplay among Planarity, Preorganization, and Substitution Effects
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Xiaobin Zhang, Sara L. Adelman, Brian T. Arko, Channa R. De Silva, Jing Su, Stosh A. Kozimor, Veronika Mocko, Jenifer C. Shafer, Benjamin W. Stein, Georg Schreckenbach, Enrique R. Batista, and Ping Yang
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Inorganic Chemistry ,Ions ,Americium ,Coordination Complexes ,Physical and Theoretical Chemistry - Abstract
Advancing the field of chemical separations is important for nearly every area of science and technology. Some of the most challenging separations are associated with the americium ion Am(III) for its extraction in the nuclear fuel cycle
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- 2022
12. Synthesis, solid-state, solution, and theoretical characterization of an 'in-cage' scandium-NOTA complex
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Kelly E. Aldrich, Ivan A. Popov, Harrison D. Root, Enrique R. Batista, Samuel M. Greer, Stosh A. Kozimor, Laura M. Lilley, Maksim Y. Livshits, Veronika Mocko, Michael T. Janicke, Brian L. Scott, Benjamin W. Stein, and Ping Yang
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Inorganic Chemistry ,Heterocyclic Compounds, 1-Ring ,Ligands ,Scandium ,Chelating Agents - Abstract
Developing chelators that strongly and selectively bind rare-earth elements (Sc, Y, La, and lanthanides) represents a longstanding fundamental challenge in inorganic chemistry. Solving these challenges is becoming more important because of increasing use of rare-earth elements in numerous technologies, ranging from paramagnets to luminescent materials. Within this context, we interrogated the complexation chemistry of the scandium(III) (Sc
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- 2022
13. Using molten salts to probe outer-coordination sphere effects on lanthanide(<scp>iii</scp>)/(<scp>ii</scp>) electron-transfer reactions
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Kristen A. Pace, Stosh A. Kozimor, Veronika Mocko, Ping Yang, Jennifer N. Wacker, Francisca R. Rocha, Cecilia Eiroa-Lledo, Molly M. MacInnes, Karah E. Knope, Nickolas H. Anderson, Enrique R. Batista, Ida M. DiMucci, Zachary R. Jones, Bo Li, Maksim Y. Livshits, and Benjamin W. Stein
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Inorganic Chemistry ,Metal ,Lanthanide ,Coordination sphere ,Absorption spectroscopy ,Oxidation state ,Chemistry ,visual_art ,visual_art.visual_art_medium ,Physical chemistry ,Molten salt ,Redox ,Ion - Abstract
Controlling structure and reactivity by manipulating the outer-coordination sphere around a given reagent represents a longstanding challenge in chemistry. Despite advances toward solving this problem, it remains difficult to experimentally interrogate and characterize outer-coordination sphere impact. This work describes an alternative approach that quantifies outer-coordination sphere effects. It shows how molten salt metal chlorides (MCln; M = K, Na, n = 1; M = Ca, n = 2) provided excellent platforms for experimentally characterizing the influence of the outer-coordination sphere cations (Mn+) on redox reactions accessible to lanthanide ions; Ln3+ + e1− → Ln2+ (Ln = Eu, Yb, Sm; e1− = electron). As a representative example, X-ray absorption spectroscopy and cyclic voltammetry results showed that Eu2+ instantaneously formed when Eu3+ dissolved in molten chloride salts that had strongly polarizing cations (like Ca2+ from CaCl2) via the Eu3+ + Cl1− → Eu2+ + ½Cl2 reaction. Conversely, molten salts with less polarizing outer-sphere M1+ cations (e.g., K1+ in KCl) stabilized Ln3+. For instance, the Eu3+/Eu2+ reduction potential was >0.5 V more positive in CaCl2 than in KCl. In accordance with first-principle molecular dynamics (FPMD) simulations, we postulated that hard Mn+ cations (high polarization power) inductively removed electron density from Lnn+ across Ln–Cl⋯Mn+ networks and stabilized electron-rich and low oxidation state Ln2+ ions. Conversely, less polarizing Mn+ cations (like K1+) left electron density on Lnn+ and stabilized electron-deficient and high-oxidation state Ln3+ ions.
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- 2021
14. ThIV–Desferrioxamine: characterization of a fluorescent bacterial probe
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Mila Nhu Lam, Maksim Y. Livshits, Kelly E. Aldrich, Stosh A. Kozimor, Laura M. Lilley, Loreen R. Stromberg, Benjamin W. Stein, Rebecca J. Abergel, Gregory L. Wagner, Harshini Mukundan, and Michael T. Janicke
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Inorganic Chemistry ,Siderophore ,chemistry.chemical_compound ,Fluorophore ,chemistry ,Fluorescence microscope ,Biophysics ,Chelation ,Nuclear magnetic resonance spectroscopy ,Fluorescence ,Conjugate - Abstract
Diversifying our ability to guard against emerging pathogenic threats is essential for keeping pace with global health challenges, including those presented by drug-resistant bacteria. Some modern diagnostic and therapeutic innovations to address this challenge focus on targeting methods that exploit bacterial nutrient sequestration pathways, such as the desferrioxamine (DFO) siderophore used by Staphylococcus aureus (S. aureus) to sequester FeIII. Building on recent studies that have shown DFO to be a versatile vehicle for chemical delivery, we show proof-of-principle that the FeIII sequestration pathway can be used to deliver a potential radiotherapeutic. Our approach replaces the FeIII nutrient sequestered by H4DFO+ with ThIV and made use of a common fluorophore, FITC, which we covalently bonded to DFO to provide a combinatorial probe for simultaneous chelation paired with imaging and spectroscopy, H3DFO_FITC. Combining insight provided from FITC-based imaging with characterization by NMR spectroscopy, we demonstrated that the fluorescent DFO_FITC conjugate retained the ThIV chelation properties of native H4DFO+. Fluorescence microscopy with both [Th(DFO_FITC)] and [Fe(DFO_FITC)] complexes showed similar uptake by S. aureus and increased intercellular accumulation as compared to the FITC and unchelated H3DFO_FITC controls. Collectively, these results demonstrate the potential for the newly developed H3DFO_FITC conjugate to be used as a targeting vector and bacterial imaging probe for S. aureus. The results presented within provide a framework to expand H4DFO+ and H3DFO_FITC to relevant radiotherapeutics (like 227Th).
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- 2021
15. Low-spin 1,1′-diphosphametallocenates of chromium and iron
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Conrad A. P. Goodwin, Benjamin W. Stein, Jaqueline L. Kiplinger, Ökten Üngör, Ross James Beattie, Brian L. Scott, and Samuel M. Greer
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Quantum chemical ,Ligand field theory ,Squid ,Materials science ,biology ,Magnetometer ,Metals and Alloys ,chemistry.chemical_element ,General Chemistry ,Catalysis ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,Chromium ,Crystallography ,chemistry ,law ,biology.animal ,Materials Chemistry ,Ceramics and Composites ,Spin (physics) ,Electron paramagnetic resonance - Abstract
We report two anionic diphosphametallocenates, [K(2.2.2-crypt)][M(PC4Me4)2] (M = Cr, 2-Cr; Fe, 2-Fe). Both are low-spin (S = ½) by EPR spectroscopy and SQUID magnetometry. This contrasts the high-spin (S = 3/2) ferrocenate, [K(2.2.2-crypt)][Fe(C5H2-1,2,4-tBu)2] (4-Fe). Quantum chemical calculations suggest this is due to significant differences in ligand field splitting of the d-orbitals which also explain structural features in the 2-M complexes.
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- 2021
16. Characterizing Polyoxovanadate‐Alkoxide Clusters Using Vanadium K‐Edge X‐Ray Absorption Spectroscopy
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Alexander S. Ditter, Samuel M. Greer, Stosh A. Kozimor, Samuel D. Weinstein, Scott R. Daly, Rachel L. Meyer, Feng Li, Veronika Mocko, Gerald T. Seidler, Samantha K. Cary, Benjamin W. Stein, Ellen M. Matson, and Anastasia V. Blake
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X-ray absorption spectroscopy ,Absorption spectroscopy ,010405 organic chemistry ,Organic Chemistry ,Vanadium ,chemistry.chemical_element ,General Chemistry ,Electronic structure ,010402 general chemistry ,01 natural sciences ,Catalysis ,0104 chemical sciences ,chemistry.chemical_compound ,Delocalized electron ,chemistry ,K-edge ,Alkoxide ,Physical chemistry ,Molecule - Abstract
A number of technologies would benefit from developing inorganic compounds and materials with specific electronic and magnetic exchange properties. Unfortunately, designing compounds with these properties is difficult because metal⋅⋅⋅metal coupling schemes are hard to predict and control. Fully characterizing communication between metals in existing compounds that exhibit interesting properties could provide valuable insight and advance those predictive capabilities. One such class of molecules are the series of Lindqvist iron-functionalized and hexavanadium polyoxovanadate-alkoxide clusters, which we characterized here using V K-edge X-ray absorption spectroscopy. Substantial changes in the pre-edge peak intensities were observed that tracked with the V 3d-electron count. The data also suggested substantial delocalization between the vanadium cations. Meanwhile, the FeIII cations were electronically isolated from the polyoxovanadate core.
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- 2020
17. Computer-Assisted Design of Macrocyclic Chelators for Actinium-225 Radiotherapeutics
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Enrique R. Batista, Amanda Morgenstern, Benjamin W. Stein, Laura M. Lilley, Ping Yang, and Stosh A. Kozimor
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Actinium ,Macrocyclic Compounds ,Static Electricity ,Ionic bonding ,chemistry.chemical_element ,Context (language use) ,010402 general chemistry ,01 natural sciences ,Inorganic Chemistry ,chemistry.chemical_compound ,Coordination Complexes ,Static electricity ,Molecule ,Chelation ,Physical and Theoretical Chemistry ,Density Functional Theory ,Chelating Agents ,Molecular Structure ,010405 organic chemistry ,Combinatorial chemistry ,0104 chemical sciences ,chemistry ,Functional group ,Computer-Aided Design ,Density functional theory ,Radiopharmaceuticals - Abstract
Actinium-225 (225Ac) is an excellent candidate for targeted radiotherapeutic applications for treating cancer, because of its 10-day half-life and emission of four high-energy α2+ particles. To harness and direct the energetic potential of actinium, strongly binding chelators that remain stable in vivo during biological targeting must be developed. Unfortunately, controlling chelation for actinium remains challenging. Actinium is the largest +3 cation on the periodic table and has a 6d05f0 electronic configuration, and its chemistry is relatively unexplored. Herein, we present theoretical work focused on improving the understanding of actinium bonding with macrocyclic chelating agents as a function of (1) macrocycle ring size, (2) the number and identity of metal binding functional groups, and (3) the length of the tether linking the metal binding functional group to the macrocyclic backbone. Actinium binding by these chelators is presented within the context of complexation with DOTA4-, the most relevant Ac3+ binding agent for contemporary radiopharmaceutical applications. The results enabled us to develop a new strategy for actinium chelator design. The approach is rooted in our identification that Ac3+-chelation chemistry is dominated by ionic bonding interactions and relies on (1) maximizing electrostatic interactions between the metal binding functional group and the Ac3+ cation and (2) minimizing electronic repulsion between negatively charged actinium binding functional groups. This insight will provide a foundation for future innovation in developing the next generation of multifunctional actinium chelators.
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- 2020
18. Spectroscopic and electrochemical characterization of a Pr
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Natalie T, Rice, Ivan A, Popov, Rebecca K, Carlson, Samuel M, Greer, Andrew C, Boggiano, Benjamin W, Stein, John, Bacsa, Enrique R, Batista, Ping, Yang, and Henry S, La Pierre
- Abstract
The molecular tetravalent oxidation state for praseodymium is observed in solution
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- 2022
19. High-Frequency and -Field Electron Paramagnetic Resonance Spectroscopic Analysis of Metal-Ligand Covalency in a 4f
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Thaige P, Gompa, Samuel M, Greer, Natalie T, Rice, Ningxin, Jiang, Joshua, Telser, Andrew, Ozarowski, Benjamin W, Stein, and Henry S, La Pierre
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The recent isolation of molecular tetravalent lanthanide complexes has enabled renewed exploration of the effect of oxidation state on the single-ion properties of the lanthanide ions. Despite the isotropic nature of the
- Published
- 2021
20. (Invited, Digital Presentation) Tuning the Electrodeposition of Actinides in Molten Alkali Halide Salts
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Molly M MacInnes, Kristen A Pace, Ida M DiMucci, Nickolas H Anderson, Benjamin W Stein, Stosh Kozimor, Francisca R Rocha, Zachary R Jones, Veronika Mocko, Enrique R Batista, Cecilia Eiroa-Lledo, Maksim Y Livshits, Jennifer N Wacker, Karah E Knope, and Ping Yang
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Molten salts have found use as solvents in numerous applications including nuclear reactors, batteries, and the extraction and purification of various metals. Unfortunately, understanding of the chemistry of molten salt solutions is limited. In this presentation we explore the use of molten salts as a testbed for understanding both outer and inner coordination sphere effects on dissolved metal ions. The electron transfer reactions available to lanthanides (Eu3+, Sm3+, and Yb3+) and actinides (U3+, U4+, and Th4+) were explored in a series of alkali and alkaline earth halide salts. We present electrochemical data that demonstrate significant shifts in the reduction potentials of these metal ions as a function of the anion and cation identities of the molten salt solvent. We hypothesize that effects on the reduction potential of these metals come from two sources: (1) the primary coordination sphere and (2) the secondary coordination sphere. The influence from the primary coordination sphere is dominated by the degree of covalency in the coordination bonds between the Lnn+ and Ann+ cations and the molten salt anions. The influence of the secondary coordination sphere is dominated by the electron-withdrawing character of the salt cations. EXAFS data and computational results that support these hypotheses are presented. Further, we provide insight into electrodeposition of the An0 metals under these conditions and highlight temperature and molten salt effects that influence these electrodepositions. Specifically, we propose that increased mobility of solid-state atoms at high temperature (> 800°C) influence the properties of electrodeposited metals.
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- 2022
21. Total Moisture Analysis of Salts by Dissolution
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Benjamin W. Stein and Nhu Lam
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Moisture analysis ,Chemistry ,Environmental chemistry ,Dissolution - Published
- 2021
22. Spectroscopic Signatures of Resonance Inhibition Reveal Differences in Donor-Bridge and Bridge-Acceptor Couplings
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Martin L. Kirk, Guangbin Wang, Roger D. Sommer, Jing Yang, Jinyuan Zhang, Daniel E. Stasiw, Diana Habel-Rodriguez, Benjamin W. Stein, and David A. Shultz
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Chemistry ,Resonance ,General Chemistry ,Configuration interaction ,Biochemistry ,Molecular physics ,Inductive coupling ,Acceptor ,Catalysis ,Electron transfer ,Colloid and Surface Chemistry ,Transition metal ,Valence bond theory ,Physics::Chemical Physics ,Ground state - Abstract
The torsional dependence of the ground state magnetic exchange coupling (J) and the corresponding electronic coupling matrix element (HDA) for eight transition metal complexes possessing donor-acceptor (D-A) biradical ligands is presented. These biradical ligands are composed of an S = 1/2 metal semiquinone (SQ) donor and an S = 1/2 nitronylnitroxide (NN) acceptor, which are coupled to each other via para-phenylene, methyl-substituted para-phenylenes, or a bicyclo[2.2.2]octane ring. The observed trends in electronic absorption and resonance Raman spectral features are in accord with a reduction in electronic and magnetic coupling between D and A units within the framework of our valence bond configuration interaction model. Moreover, our spectroscopic results highlight different orbital mechanisms that modulate coupling in these complexes, which is not manifest in the ferromagnetic JSQ-B-NN values. The work provides new detailed insight into the effects of torsional rotations which contribute to inhomogeneities in experimentally determined exchange couplings, electron transfer rates, and electron transport conductance measurements.
- Published
- 2020
23. Preparation of an Actinium-228 Generator
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Laura M. Lilley, Benjamin W. Stein, Stosh A. Kozimor, Veronika Mocko, Kelly E. Aldrich, Cecilia Eiroa-Lledo, and Mila Nhu Lam
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Inorganic Chemistry ,Actinium ,Generator (computer programming) ,High specific activity ,Chemistry ,Radiochemistry ,Nuclear spectroscopy ,chemistry.chemical_element ,Physical and Theoretical Chemistry ,Volume concentration - Abstract
Advances in targeted α-therapies have increased the interest in actinium (Ac), whose chemistry is poorly defined due to scarcity and radiological hazards. Challenges associated with characterizing Ac3+ chemistry are magnified by its 5f06d0 electronic configuration, which precludes the use of many spectroscopic methods amenable to small amounts of material and low concentrations (like EPR, UV-vis, fluorescence). In terms of nuclear spectroscopy, many actinium isotopes (225Ac and 227Ac) are equally "unfriendly" because the actinium α-, β-, and γ-emissions are difficult to resolve from the actinium daughters. To address these issues, we developed a method for isolating an actinium isotope (228Ac) whose nuclear properties are well-suited for γ-spectroscopy. This four-step procedure isolates 228Ra from naturally occurring 232Th. The relatively long-lived 228Ra (t1/2 = 5.75(3) years) radioisotope subsequently decays to 228Ac. Because the 228Ac decay rate [t1/2 = 6.15(2) h] is fast, 228Ac rapidly regenerates after being harvested from the 228Ra parent. The resulting 228Ac generator provides frequent and long-term access (of many years) to the spectroscopically "friendly" 228Ac radionuclide. We have demonstrated that the 228Ac product can be routinely "milked" from this generator on a daily basis, in chemically pure form, with high specific activity and in excellent yield (∼95%). Hence, in the same way that developing synthesis routes to new starting materials has advanced coordination chemistry for many metals by broadening access, this 228Ac generator has the potential to broaden actinium access for the inorganic community, facilitating the characterization of actinium chemical behavior.
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- 2020
24. Ground State Nuclear Magnetic Resonance Chemical Shifts Predict Charge-Separated Excited State Lifetimes
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Dominic K. Kersi, Casseday P. Richers, Changjian Feng, Logan J. Giles, Ranjana Dangi, David A. Shultz, Jing Yang, Christopher R. Tichnell, Benjamin W. Stein, and Martin L. Kirk
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X-ray absorption spectroscopy ,Chemistry ,Chemical shift ,02 engineering and technology ,Carbon-13 NMR ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,Acceptor ,0104 chemical sciences ,Inorganic Chemistry ,Chalcogen ,Excited state ,Physical and Theoretical Chemistry ,0210 nano-technology ,Ground state ,Diimine - Abstract
Dichalcogenolene platinum(II) diimine complexes, (LE,E′)Pt(bpy), are characterized by charge-separated dichalcogenolene donor (LE,E′) → diimine acceptor (bpy) ligand-to-ligand charge transfer (LL′CT) excited states that lead to their interesting photophysics and potential use in solar energy conversion applications. Despite the intense interest in these complexes, the chalcogen dependence on the lifetime of the triplet LL′CT excited state remains unexplained. Three new (LE,E′)Pt(bpy) complexes with mixed chalcogen donors exhibit decay rates that are dominated by a spin–orbit mediated nonradiative pathway, the magnitude of which is proportional to the anisotropic covalency provided by the mixed-chalcogen donor ligand environment. This anisotropic covalency is dramatically revealed in the 13C NMR chemical shifts of the donor carbons that bear the chalcogens and is further probed by S K-edge XAS. Remarkably, the NMR chemical shift differences also correlate with the spin–orbit matrix element that connects th...
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- 2018
25. Advancing Chelation Chemistry for Actinium and Other +3 f-Elements, Am, Cm, and La
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Eva R. Birnbaum, Stosh A. Kozimor, Brian L. Scott, Veronika Mocko, Samantha K. Cary, Ping Yang, Kevin D. John, Amanda Morgenstern, Benjamin W. Stein, Maryline G. Ferrier, Enrique R. Batista, Sharon E. Bone, and Juan S. Lezama Pacheco
- Subjects
Actinium ,Inorganic chemistry ,Binding pocket ,chemistry.chemical_element ,010402 general chemistry ,Ligands ,01 natural sciences ,Biochemistry ,Catalysis ,Coordination complex ,Colloid and Surface Chemistry ,Organophosphorus Compounds ,Coordination Complexes ,Lanthanum ,Molecule ,Chelation ,Chelating Agents ,chemistry.chemical_classification ,Americium ,Extended X-ray absorption fine structure ,Molecular Structure ,Extramural ,General Chemistry ,0104 chemical sciences ,chemistry ,Curium ,Radiopharmaceuticals - Abstract
A major chemical challenge facing implementation of 225Ac in targeted alpha therapy-an emerging technology that has potential for treatment of disease-is identifying an 225Ac chelator that is compatible with in vivo applications. It is unclear how to tailor a chelator for Ac binding because Ac coordination chemistry is poorly defined. Most Ac chemistry is inferred from radiochemical experiments carried out on microscopic scales. Of the few Ac compounds that have been characterized spectroscopically, success has only been reported for simple inorganic ligands. Toward advancing understanding in Ac chelation chemistry, we have developed a method for characterizing Ac complexes that contain highly complex chelating agents using small quantities (μg) of 227Ac. We successfully characterized the chelation of Ac3+ by DOTP8- using EXAFS, NMR, and DFT techniques. To develop confidence and credibility in the Ac results, comparisons with +3 cations (Am, Cm, and La) that could be handled on the mg scale were carried out. We discovered that all M3+ cations (M = Ac, Am, Cm, La) were completely encapsulated within the binding pocket of the DOTP8- macrocycle. The computational results highlighted the stability of the M(DOTP)5- complexes.
- Published
- 2019
26. Long-range spin dependent delocalization promoted by the pseudo Jahn-Teller effect
- Author
-
Diane A. Dickie, Benjamin W. Stein, David A. Shultz, Martin L. Kirk, David J. R. Brook, and Sachin Nedungadi
- Subjects
Physics ,010304 chemical physics ,Spins ,General Physics and Astronomy ,Triad (anatomy) ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Delocalized electron ,Crystallography ,medicine.anatomical_structure ,Ferromagnetism ,0103 physical sciences ,medicine ,Single bond ,Diamagnetism ,Antiferromagnetism ,Physical and Theoretical Chemistry ,Spin (physics) - Abstract
Strong spin-dependent delocalization (double exchange) was previously demonstrated for the complexes, NN-Bridge-SQ-Coiii(py)2Cat-Bridge-NN (where NN = S = 12 nitronylnitroxide, Bridge = 1,4-phenylene and single bond, SQ = S = 12 orthobenzosemiquinone, Coiii = low-spin d6 cobalt 3+, and Cat = diamagnetic catecholate). The mixed-valent S = 12 SQ-Coiii-Cat triad results in ferromagnetic alignment of localized (pinned) NN spins which are ∼22 A apart (Bridge = Ph). Herein, we report similar ferromagnetic coupling of localized verdazyl (Vdz) radical spins. The origin of the magnetic exchange results from a second order vibronic effect (pseudo Jahn-Teller effect) in [Vdz-diox-Ru(py)2-diox-Vdz]0, which possesses a diamagnetic [diox-Ru-diox]0 triad by virtue of strong antiferromagnetic SQ-Ruiii exchange.
- Published
- 2019
27. Redox-Active vs Redox-Innocent: A Comparison of Uranium Complexes Containing Diamine Ligands
- Author
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Matthias Zeller, Kimberly C. Mullane, Suzanne C. Bart, Eric J. Schelter, Sharon E. Bone, Phillip E. Fanwick, Scott A. Pattenaude, Stosh A. Kozimor, Juan S. Lezama Pacheco, Maryline G. Ferrier, and Benjamin W. Stein
- Subjects
Steric effects ,Absorption spectroscopy ,010405 organic chemistry ,Chemistry ,Ligand ,chemistry.chemical_element ,Uranium ,010402 general chemistry ,01 natural sciences ,Redox ,Medicinal chemistry ,0104 chemical sciences ,Inorganic Chemistry ,chemistry.chemical_compound ,Diamine ,Redox active ,Physical and Theoretical Chemistry ,Diimine - Abstract
Uranium complexes (MesDAE)2U(THF) (1-DAE) and Cp2U(MesDAE) (2-DAE) (MesDAE = [ArN-CH2CH2-NAr]; Ar = 2,4,6-trimethylphenyl (Mes)), bearing redox-innocent diamide ligands, have been synthesized and characterized for a full comparison with previously published, redox-active diimine complexes, (MesDABMe)2U(THF) (1-DAB) and Cp2U(MesDABMe) (2-DAB) (MesDABMe = [ArN═C(Me)C(Me)═NAr]; Ar = Mes). These redox-innocent analogues maintain an analogous steric environment to their redox-active ligand counterparts to facilitate a study aimed at determining the differing electronic behavior around the uranium center. Structural analysis by X-ray crystallography showed 1-DAE and 2-DAE have a structural environment very similar to 1-DAB and 2-DAB, respectively. The main difference occurs with coordination of the ene-backbone to the uranium center in the latter species. Electronic absorption spectroscopy reveals these new DAE complexes are nearly identical to each other. X-ray absorption spectroscopy suggests all four species...
- Published
- 2018
28. Advancing Understanding of the +4 Metal Extractant Thenoyltrifluoroacetonate (TTA–); Synthesis and Structure of MIVTTA4 (MIV = Zr, Hf, Ce, Th, U, Np, Pu) and MIII(TTA)4– (MIII = Ce, Nd, Sm, Yb)
- Author
-
Samantha K. Cary, Benjamin W. Stein, Maksim Y. Livshits, Brian L. Scott, Stosh A. Kozimor, Veronika Mocko, Jeffrey J. Rack, Justin N. Cross, and Maryline G. Ferrier
- Subjects
Highly skilled ,010405 organic chemistry ,Extraction (chemistry) ,chemistry.chemical_element ,Actinide ,Uranium ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,Metal ,chemistry.chemical_compound ,chemistry ,visual_art ,visual_art.visual_art_medium ,Physical chemistry ,Physical and Theoretical Chemistry ,Thenoyltrifluoroacetone - Abstract
Thenoyltrifluoroacetone (HTTA)-based extractions represent popular methods for separating microscopic amounts of transuranic actinides (i.e., Np and Pu) from macroscopic actinide matrixes (e.g. bulk uranium). It is well-established that this procedure enables +4 actinides to be selectively removed from +3, + 5, and +6 f-elements. However, even highly skilled and well-trained researchers find this process complicated and (at times) unpredictable. It is difficult to improve the HTTA extraction—or find alternatives—because little is understood about why this separation works. Even the identities of the extracted species are unknown. In addressing this knowledge gap, we report here advances in fundamental understanding of the HTTA-based extraction. This effort included comparatively evaluating HTTA complexation with +4 and +3 metals (MIV = Zr, Hf, Ce, Th, U, Np, and Pu vs MIII = Ce, Nd, Sm, and Yb). We observed +4 metals formed neutral complexes of the general formula MIV(TTA)4. Meanwhile, +3 metals formed an...
- Published
- 2018
29. A series of F-Element chelators; diaza crown ethers functionalized with catecholate binding substituents
- Author
-
Samantha K. Cary, Eva R. Birnbaum, Benjamin W. Stein, Stosh A. Kozimor, Brian L. Scott, Veronika Mocko, and John M. Berg
- Subjects
Catechol ,Semiquinone ,010405 organic chemistry ,Chemistry ,Organic Chemistry ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Combinatorial chemistry ,Redox ,0104 chemical sciences ,Inorganic Chemistry ,chemistry.chemical_compound ,Elemental analysis ,Materials Chemistry ,Cluster (physics) ,Physical and Theoretical Chemistry ,Spectroscopy ,Single crystal ,Mannich reaction - Abstract
Reported here is the preparation of azacrown ethers functionalized with catechol groups. The synthetic approach was (1st) novel in that it made use of the Mannich reaction and (2nd) valuable in that it provided an improved synthesis (in terms of practical deployment) of the known N,N′-bis(2,3-dihydroxybenzyl)-4,13-diaza-18-crown-6, H4ChaCha. Moreover, it demonstrated potential application of the synthetic method for accommodating a wide range of catecholate functionalities by using the synthetic strategy to prepare N,N′-bis(2,3-dihydroxy-5-tert-butylbenzyl)-4,13-diaza-18-crown-6 (H4tBu2ChaCha) for the first time. These H4ChaCha and H4tBu2ChaCha macrocycles offer exciting opportunity to expand redox chemistry for the f-elements. As “proof-of-principle,” we isolated the unusual tetrameric cluster [La2(tBuChaCha)2]2 from reactions between H4tBu2ChaCha and La[N(SiMe3)2]3. Characterization of [La2(tBuChaCha)2]2 by elemental analysis, single crystal X-ray diffraction, IR, and UV–vis–NIR spectroscopy suggested that the complex represented a rare example of an f-element semiquinone. It further demonstrated that the combination of La3+ and H4tBu2ChaCha provided access to one-electron oxidation chemistry within redox potential windows that were amenable to mild reaction conditions.
- Published
- 2018
30. The coordination chemistry of CmIII, AmIII, and AcIIIin nitrate solutions: an actinide L3-edge EXAFS study
- Author
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Gerald T. Seidler, Stosh A. Kozimor, Veronika Mocko, Sharon E. Bone, Juan S. Lezama Pacheco, Maryline G. Ferrier, Alexander S. Ditter, Samantha K. Cary, and Benjamin W. Stein
- Subjects
chemistry.chemical_classification ,X-ray absorption spectroscopy ,Aqueous solution ,Extended X-ray absorption fine structure ,Absorption spectroscopy ,010405 organic chemistry ,Chemistry ,Analytical chemistry ,General Chemistry ,Actinide ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Coordination complex ,chemistry.chemical_compound ,Nitric acid ,Stoichiometry - Abstract
Understanding actinide(III) (AnIII = CmIII, AmIII, AcIII) solution-phase speciation is critical for controlling many actinide processing schemes, ranging from medical applications to reprocessing of spent nuclear fuel. Unfortunately, in comparison to most elements in the periodic table, AnIII speciation is often poorly defined in complexing aqueous solutions and in organic media. This neglect – in large part – is a direct result of the radioactive properties of these elements, which make them difficult to handle and acquire. Herein, we surmounted some of the handling challenges associated with these exotic 5f-elements and characterized CmIII, AmIII, and AcIII using AnIII L3-edge X-ray absorption spectroscopy (XAS) as a function of increasing nitric acid (HNO3) concentration. Our results revealed that actinide aquo ions, An(H2O)x3+ (x = 9.6 ± 0.7, 8.9 ± 0.8, and 10.0 ± 0.9 for CmIII, AmIII, and AcIII), were the dominant species in dilute HNO3 (0.05 M). In concentrated HNO3 (16 M), shell-by-shell fitting of the extended X-ray fine structure (EXAFS) data showed the nitrate complexation increased, such that the average stoichiometries of Cm(NO3)4.1±0.7(H2O)5.7±1.3(1.1±0.2)−, Am(NO3)3.4±0.7(H2O)5.4±0.5(0.4±0.1)−, and Ac(NO3)2.3±1.7(H2O)8.3±5.2(0.7±0.5)+ were observed. Data obtained at the intermediate HNO3 concentration (4 M) were modeled as a linear combination of the 0.05 and 16 M spectra. For all three metals, the intermediate models showed larger contributions from the 0.05 M HNO3 spectra than from the 16 M HNO3 spectra. Additionally, these efforts enabled the Cm–NO3 and Ac–NO3 distances to be measured for the first time. Moreover, the AnIII L3-edge EXAFS results, contribute to the growing body of knowledge associated with CmIII, AmIII, and AcIII coordination chemistry, in particular toward advancing understanding of AnIII solution phase speciation.
- Published
- 2018
31. Measurement of 227Ac impurity in 225Ac using decay energy spectroscopy
- Author
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Michael Yoho, Ellen M. O'Brien, Laura M. Lilley, Joel N. Ullom, M. H. Carpenter, Katrina Koehler, Benjamin W. Stein, M. P. Croce, Chandler M. Smith, David J. Mercer, A.D. Tollefson, Michael E. Fassbender, and Daniel Schmidt
- Subjects
Superconductivity ,Phase transition ,Radiation ,Materials science ,Analytical chemistry ,chemistry.chemical_element ,010403 inorganic & nuclear chemistry ,01 natural sciences ,Spectral line ,030218 nuclear medicine & medical imaging ,0104 chemical sciences ,03 medical and health sciences ,Actinium ,0302 clinical medicine ,chemistry ,Decay energy ,Impurity ,Transition edge sensor ,Spectroscopy - Abstract
225 Ac is a valuable medical radionuclide for targeted α therapy, but 227 Ac is an undesirable byproduct of an accelerator-based synthesis method under investigation. Sufficient detector sensitivity is critical for quantifying the trace impurity of 227 Ac , with the 227 Ac / 225 Ac activity ratio predicted to be approximately 0.15% by end-of-bombardment (EOB). Superconducting transition edge sensor (TES) microcalorimeters offer high resolution energy spectroscopy using the normal-to-superconducting phase transition to measure small changes in temperature. By embedding 225 Ac production samples in a gold foil thermally coupled to a TES microcalorimeter we can measure the decay energies of the radionuclides embedded with high resolution and 100% detection efficiency. This technique, known as decay energy spectroscopy (DES), collapses several peaks from α decays into single Q-value peaks. In practice there are more complex factors in the interpretation of data using DES, which we will discuss herein. Using this technique we measured the EOB 227 Ac impurity to be (0.142 ± 0.005)% for a single production sample. This demonstration has shown that DES is a useful tool for quantitative measurements of complicated spectra.
- Published
- 2021
32. Charge Transfer Doping Induced Conformational Ordering of a Non-Crystalline Conjugated Polymer
- Author
-
Martin L. Kirk, Hua Guo, Benjamin W. Stein, John K. Grey, Alan K. Thomas, and Ryan Johnson
- Subjects
Materials science ,Stereochemistry ,02 engineering and technology ,Conjugated system ,010402 general chemistry ,01 natural sciences ,law.invention ,symbols.namesake ,chemistry.chemical_compound ,law ,Physical and Theoretical Chemistry ,Electron paramagnetic resonance ,Conformational isomerism ,chemistry.chemical_classification ,Dopant ,Doping ,Polymer ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Crystallography ,General Energy ,Monomer ,chemistry ,symbols ,0210 nano-technology ,Raman spectroscopy - Abstract
Charge transfer doping of a nominally disordered conjugated polymer induces long-range conformational ordering (stiffening) of backbone segments. Addition of [2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) to dilute solutions of poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) results in quantitative charge transfer in the ground electronic state of the polymer. Following charge (hole) injection, greater MDMO-PPV monomer coplanarity is evident in electronic, Raman, and electron paramagnetic resonance (EPR) spectra over a broad range of dopant loadings. New transitions emerge at lower energies with spectral patterns distinct from pristine materials but closely resemble minority low energy conformers selectively that can be prepared by careful control of processing conditions. We further demonstrate that characteristic Raman patterns of PPV systems actually contain signatures of a minority ordered form that interacts preferentially with the dopant. Subsequent additions of dopant al...
- Published
- 2017
33. Covalency in Americium(III) Hexachloride
- Author
-
Stosh A. Kozimor, Justin N. Cross, Brian L. Scott, Samantha K. Cary, Ping Yang, Enrique R. Batista, Cory J. Windorff, Benjamin W. Stein, William J. Evans, Jing Su, and Veronika Mocko
- Subjects
X-ray absorption spectroscopy ,Americium ,Absorption spectroscopy ,010405 organic chemistry ,Chemistry ,Extramural ,chemistry.chemical_element ,General Chemistry ,Electronic structure ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,Colloid and Surface Chemistry ,Chlorides ,Chemical physics ,Computational chemistry ,Mixing (physics) - Abstract
Developing a better understanding of covalency (or orbital mixing) is of fundamental importance. Covalency occupies a central role in directing chemical and physical properties for almost any given compound or material. Hence, the concept of covalency has potential to generate broad and substantial scientific advances, ranging from biological applications to condensed matter physics. Given the importance of orbital mixing combined with the difficultly in measuring covalency, estimating or inferring covalency often leads to fiery debate. Consider the 60-year controversy sparked by Seaborg and co-workers ( Diamond, R. M.; Street, K., Jr.; Seaborg, G. T. J. Am. Chem. Soc. 1954 , 76 , 1461 ) when it was proposed that covalency from 5f-orbitals contributed to the unique behavior of americium in chloride matrixes. Herein, we describe the use of ligand K-edge X-ray absorption spectroscopy (XAS) and electronic structure calculations to quantify the extent of covalent bonding in-arguably-one of the most difficult systems to study, the Am-Cl interaction within AmCl
- Published
- 2017
34. Evaluating the electronic structure of formal LnIIions in LnII(C5H4SiMe3)31−using XANES spectroscopy and DFT calculations
- Author
-
Juan S. Lezama Pacheco, Gregory L. Wagner, Enrique R. Batista, David H. Woen, Jing Su, Austin J. Ryan, Maryline G. Ferrier, Stosh A. Kozimor, Samantha K. Cary, Jonathan W. Engle, Tonya Vitova, Benjamin W. Stein, Ping Yang, Angela C. Olson, William J. Evans, and Megan E. Fieser
- Subjects
Lanthanide ,010405 organic chemistry ,Chemistry ,Transition dipole moment ,General Chemistry ,Electronic structure ,010402 general chemistry ,01 natural sciences ,XANES ,0104 chemical sciences ,Ion ,Computational chemistry ,Physical chemistry ,Density functional theory ,Electron configuration ,Spectroscopy - Abstract
The isolation of [K(2.2.2-cryptand)][Ln(C5H4SiMe3)3], formally containing LnII, for all lanthanides (excluding Pm) was surprising given that +2 oxidation states are typically regarded as inaccessible for most 4f-elements. Herein, X-ray absorption near-edge spectroscopy (XANES), ground-state density functional theory (DFT), and transition dipole moment calculations are used to investigate the possibility that Ln(C5H4SiMe3)31- (Ln = Pr, Nd, Sm, Gd, Tb, Dy, Y, Ho, Er, Tm, Yb and Lu) compounds represented molecular LnII complexes. Results from the ground-state DFT calculations were supported by additional calculations that utilized complete-active-space multi-configuration approach with second-order perturbation theoretical correction (CASPT2). Through comparisons with standards, Ln(C5H4SiMe3)31- (Ln = Sm, Tm, Yb, Lu, Y) are determined to contain 4f6 5d0 (SmII), 4f13 5d0 (TmII), 4f14 5d0 (YbII), 4f14 5d1 (LuII), and 4d1 (YII) electronic configurations. Additionally, our results suggest that Ln(C5H4SiMe3)31- (Ln = Pr, Nd, Gd, Tb, Dy, Ho, and Er) also contain LnII ions, but with 4f n 5d1 configurations (not 4f n+1 5d0). In these 4f n 5d1 complexes, the C3h-symmetric ligand environment provides a highly shielded 5d-orbital of a' symmetry that made the 4f n 5d1 electronic configurations lower in energy than the more typical 4f n+1 5d0 configuration.
- Published
- 2017
35. Wave Function Control of Charge-Separated Excited-State Lifetimes
- Author
-
David R Daley, David A. Shultz, Martin L. Kirk, Christopher R. Tichnell, Evgeny O. Danilov, and Benjamin W. Stein
- Subjects
Spins ,Chemistry ,General Chemistry ,Electronic structure ,Biochemistry ,Catalysis ,Colloid and Surface Chemistry ,Unpaired electron ,Excited state ,Ultrafast laser spectroscopy ,Atomic physics ,Wave function ,Ground state ,Spin (physics) - Abstract
Control of excited-state processes is crucial to an increasing number of important device technologies that include displays, photocatalysts, solar energy conversion devices, photovoltaics, and photonics. However, the manipulation and control of electronic excited-state lifetimes and properties continue to be a challenge for molecular scientists. Herein, we present the results of ground-state and transient absorption spectroscopies as they relate to magnetic exchange control of excited-state lifetimes. We describe a novel mechanism for controlling these excited-state lifetimes that involves varying the magnetic exchange interaction between a stable organic radical and the unpaired electrons present in the open-shell configuration of a charge-separated excited state. Specifically, we show that the excited-state lifetime can be controlled in a predictable manner based on an a priori knowledge of the pairwise magnetic exchange interactions between excited-state spins. These magnetic exchange couplings affect the excited-state electronic structure in a manner that introduces variable degrees of spin forbiddenness into the nonradiative decay channel between the excited state and the electronic ground state.
- Published
- 2019
36. Examining the Effects of Ligand Variation on the Electronic Structure of Uranium Bis(imido) Species
- Author
-
Stosh A. Kozimor, Juan S. Lezama Pacheco, John J. Kiernicki, Suzanne C. Bart, Henry S. La Pierre, Benjamin W. Stein, Matthias Zeller, and Maryline G. Ferrier
- Subjects
chemistry.chemical_classification ,Double bond ,010405 organic chemistry ,Ligand ,Stereochemistry ,Substituent ,chemistry.chemical_element ,General Chemistry ,Electronic structure ,Uranium ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,chemistry ,Pyridine ,Diimine - Abstract
Arylazide and diazene activation by highly reduced uranium(IV) complexes bearing trianionic redox-active pyridine(diimine) ligands, [CpPU(MesPDIMe)]2 (1-CpP), Cp*U(MesPDIMe)(THF) (1-Cp*) (CpP = 1-(7,7-dimethylbenzyl)cyclopentadienide; Cp* = η5-1,2,3,4,5-pentamethylcyclopentadienide), and Cp*U(tBu-MesPDIMe) (THF) (1-tBu) (2,6-((Mes)N═CMe)2-p-R-C5H2N, Mes = 2,4,6-trimethylphenyl; R = H, MesPDIMe; R = C(CH3)3, tBu-MesPDIMe), has been investigated. While 1-Cp* and 1-CpP readily reduce N3R (R = Ph, p-tolyl) to form trans-bis(imido) species, CpPU(NAr)2(MesPDIMe) (Ar = Ph, 2-CpP; Ar = p-Tol, 3-CpP) and Cp*U(NPh)2(MesPDIMe) (2-Cp*), only 1-Cp* can cleave diazene N═N double bonds to form the same product. Complexes 2-Cp*, 2-CpP, and 3-CpP are uranium(V) trans-bis(imido) species supported by neutral [MesPDIMe]0 ligands formed by complete oxidation of [MesPDIMe]3– ligands of 1-CpP and 1-Cp*. Variation of the arylimido substituent in 2-Cp* from phenyl to p-tolyl, forming Cp*U(NTol)2(MesPDIMe) (3-Cp*), changes the ele...
- Published
- 2016
37. Comparing the 2,2′‐Biphenylenedithiophosphinate Binding of Americium with Neodymium and Europium
- Author
-
Justin N. Cross, Joseph A. Macor, Jeffery A. Bertke, Maryline G. Ferrier, Gregory S. Girolami, Stosh A. Kozimor, Joel R. Maassen, Brian L. Scott, David K. Shuh, Benjamin W. Stein, and S. Chantal E. Stieber
- Subjects
010405 organic chemistry ,General Medicine ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences - Abstract
© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Advancing our understanding of the minor actinides (Am, Cm) versus lanthanides is key for developing advanced nuclear-fuel cycles. Herein, we describe the preparation of (NBu4)Am[S2P(tBu2C12H6)]4and two isomorphous lanthanide complexes, namely one with a similar ionic radius (i.e., NdIII) and an isoelectronic one (EuIII). The results include the first measurement of an Am−S bond length, with a mean value of 2.921(9) Å, by single-crystal X-ray diffraction. Comparison with the EuIIIand NdIIIcomplexes revealed subtle electronic differences between the complexes of AmIIIand the lanthanides.
- Published
- 2016
38. The coordination chemistry of Cm
- Author
-
Maryline G, Ferrier, Benjamin W, Stein, Sharon E, Bone, Samantha K, Cary, Alexander S, Ditter, Stosh A, Kozimor, Juan S, Lezama Pacheco, Veronika, Mocko, and Gerald T, Seidler
- Subjects
Chemistry - Abstract
CmIII, AmIII, and AcIII have been characterized by solution L3-edge X-ray absorption spectroscopy as a function of nitric acid concentration. This enabled the first experimental determination of Cm and Ac nitrate distances., Understanding actinide(iii) (AnIII = CmIII, AmIII, AcIII) solution-phase speciation is critical for controlling many actinide processing schemes, ranging from medical applications to reprocessing of spent nuclear fuel. Unfortunately, in comparison to most elements in the periodic table, AnIII speciation is often poorly defined in complexing aqueous solutions and in organic media. This neglect – in large part – is a direct result of the radioactive properties of these elements, which make them difficult to handle and acquire. Herein, we surmounted some of the handling challenges associated with these exotic 5f-elements and characterized CmIII, AmIII, and AcIII using AnIII L3-edge X-ray absorption spectroscopy (XAS) as a function of increasing nitric acid (HNO3) concentration. Our results revealed that actinide aquo ions, An(H2O)x3+ (x = 9.6 ± 0.7, 8.9 ± 0.8, and 10.0 ± 0.9 for CmIII, AmIII, and AcIII), were the dominant species in dilute HNO3 (0.05 M). In concentrated HNO3 (16 M), shell-by-shell fitting of the extended X-ray fine structure (EXAFS) data showed the nitrate complexation increased, such that the average stoichiometries of Cm(NO3)4.1±0.7(H2O)5.7±1.3(1.1±0.2)–, Am(NO3)3.4±0.7(H2O)5.4±0.5(0.4±0.1)–, and Ac(NO3)2.3±1.7(H2O)8.3±5.2(0.7±0.5)+ were observed. Data obtained at the intermediate HNO3 concentration (4 M) were modeled as a linear combination of the 0.05 and 16 M spectra. For all three metals, the intermediate models showed larger contributions from the 0.05 M HNO3 spectra than from the 16 M HNO3 spectra. Additionally, these efforts enabled the Cm–NO3 and Ac–NO3 distances to be measured for the first time. Moreover, the AnIII L3-edge EXAFS results, contribute to the growing body of knowledge associated with CmIII, AmIII, and AcIII coordination chemistry, in particular toward advancing understanding of AnIII solution phase speciation.
- Published
- 2018
39. Separation of Protactinium Employing Sulfur-Based Extraction Chromatographic Resins
- Author
-
Lance E. Wyant, Eva R. Birnbaum, Michael E. Fassbender, Roy Copping, Stosh A. Kozimor, Mark Brugh, Allison Owens, T. Gannon Parker, Tara Mastren, Valery Radchenko, F. Meiring Nortier, Benjamin W. Stein, and Kevin D. John
- Subjects
Fission products ,Chromatography ,Molecular Structure ,010405 organic chemistry ,Surface Properties ,Extraction (chemistry) ,Protactinium ,Thorium ,chemistry.chemical_element ,Uranium ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Analytical Chemistry ,Radium ,Actinium ,Resins, Synthetic ,chemistry ,Yield (chemistry) ,Thymidine - Abstract
Protactinium-230 (t1/2 = 17.4 d) is the parent isotope of 230U (t1/2 = 20.8 d), a radionuclide of interest for targeted alpha therapy (TAT). Column chromatographic methods have been developed to separate no-carrier-added 230Pa from proton irradiated thorium targets and accompanying fission products. Results reported within demonstrate the use of novel sulfur bearing chromatographic extraction resins for the selective separation of protactinium. The recovery yield of 230Pa was 93 ± 4% employing a R3P═S type commercially available resin and 88 ± 4% employing a DGTA (diglycothioamide) containing custom synthesized extraction chromatographic resin. The radiochemical purity of the recovered 230Pa was measured via high purity germanium γ-ray spectroscopy to be >99.5% with the remaining radioactive contaminant being 95Nb due to its similar chemistry to protactinium. Measured equilibrium distribution coefficients for protactinium, thorium, uranium, niobium, radium, and actinium on both the R3P═S type and the DGTA...
- Published
- 2018
40. Advancing Understanding of the +4 Metal Extractant Thenoyltrifluoroacetonate (TTA
- Author
-
Samantha K, Cary, Maksim, Livshits, Justin N, Cross, Maryline G, Ferrier, Veronika, Mocko, Benjamin W, Stein, Stosh A, Kozimor, Brian L, Scott, and Jeffrey J, Rack
- Abstract
Thenoyltrifluoroacetone (HTTA)-based extractions represent popular methods for separating microscopic amounts of transuranic actinides (i.e., Np and Pu) from macroscopic actinide matrixes (e.g. bulk uranium). It is well-established that this procedure enables +4 actinides to be selectively removed from +3, + 5, and +6 f-elements. However, even highly skilled and well-trained researchers find this process complicated and (at times) unpredictable. It is difficult to improve the HTTA extraction-or find alternatives-because little is understood about why this separation works. Even the identities of the extracted species are unknown. In addressing this knowledge gap, we report here advances in fundamental understanding of the HTTA-based extraction. This effort included comparatively evaluating HTTA complexation with +4 and +3 metals (M
- Published
- 2018
41. Excited State Magnetic Exchange Interactions Enable Large Spin Polarization Effects
- Author
-
David A. Shultz, Christopher R. Tichnell, Benjamin W. Stein, Ju Chen, and Martin L. Kirk
- Subjects
Photon ,Spin polarization ,Spintronics ,010405 organic chemistry ,Chemistry ,General Chemistry ,Electron ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,Colloid and Surface Chemistry ,Intersystem crossing ,Excited state ,Multiplicity (chemistry) ,Atomic physics ,Spin (physics) - Abstract
Excited state processes involving multiple electron spin centers are crucial elements for both spintronics and quantum information processing. Herein, we describe an addressable excited state mechanism for precise control of electron spin polarization. This mechanism derives from excited state magnetic exchange couplings that occur between the electron spins of a photogenerated electron-hole pair and that of an organic radical. The process is initiated by absorption of a photon followed by ultrafast relaxation within the excited state spin manifold. This leads to dramatic changes in spin polarization between excited states of the same multiplicity. Moreover, this photoinitiated spin polarization process can be "read" spectroscopically using a magnetooptical technique that is sensitive to the excited state electron spin polarizations and allows for the evaluation of wave functions that give rise to these polarizations. This system is unique in that it requires neither intersystem crossing nor magnetic resonance techniques to create dynamic spin-polarization effects in molecules.
- Published
- 2018
42. Enhanced Charge Transfer Doping Efficiency in J-Aggregate Poly(3-hexylthiophene) Nanofibers
- Author
-
Martin L. Kirk, Jose A. Garcia, Jing Yang, Jian Gao, Benjamin W. Stein, John K. Grey, and Alan K. Thomas
- Subjects
Materials science ,Dopant ,Doping ,Analytical chemistry ,Polaron ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,symbols.namesake ,General Energy ,law ,Nanofiber ,symbols ,Physical and Theoretical Chemistry ,Absorption (electromagnetic radiation) ,Electron paramagnetic resonance ,Raman spectroscopy ,J-aggregate - Abstract
Charge transfer doping efficiencies of π-stacked poly(3-hexylthiophene) (P3HT) aggregate nanofibers are studied using spectroscopic and electron microscopy probes. Solution dispersions of self-assembled P3HT nanofibers are doped in the ground electronic state by adding varying amounts (w/w%) of the strong charge transfer dopant 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ). Careful control of self-assembly conditions allows us to select either the H- and J-aggregate limiting forms, which differ primarily in the degree of purity (i.e., molecular weight fractionation) and nanomorphology. Electron paramagnetic resonance (EPR), electronic absorption, and Raman spectroscopy of F4-TCNQ–:P3HT+ species are then used to track doping efficiency with dopant loading. J-aggregate nanofibers exhibit over an order of magnitude larger doping efficiencies than polymorphic H-aggregate nanofibers. The higher purity and order of the former promote intrachain polaron delocalization whereas disorder arising fr...
- Published
- 2015
43. Electronic structure contributions to reactivity in xanthine oxidase family enzymes
- Author
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Martin L. Kirk and Benjamin W. Stein
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Models, Molecular ,Xanthine Oxidase ,Protein Conformation ,Stereochemistry ,chemistry.chemical_element ,Electrons ,Crystallography, X-Ray ,Xanthine ,Biochemistry ,Aldehyde ,Article ,Catalysis ,Inorganic Chemistry ,chemistry.chemical_compound ,Multienzyme Complexes ,Organic chemistry ,Reactivity (chemistry) ,Xanthine oxidase ,Molybdenum ,chemistry.chemical_classification ,biology ,Electron Spin Resonance Spectroscopy ,Active site ,Aldehyde Oxidoreductases ,chemistry ,Xanthine dehydrogenase ,biology.protein ,Oxidation-Reduction ,Carbon monoxide dehydrogenase - Abstract
We review the xanthine oxidase (XO) family of pyranopterin molybdenum enzymes with a specific emphasis on electronic structure contributions to reactivity. In addition to xanthine and aldehyde oxidoreductases, which catalyze the two-electron oxidation of aromatic heterocycles and aldehyde substrates, this mini-review highlights recent work on the closely related carbon monoxide dehydrogenase (CODH) that catalyzes the oxidation of CO using a unique Mo-Cu heterobimetallic active site. A primary focus of this mini-review relates to how spectroscopy and computational methods have been used to develop an understanding of critical relationships between geometric structure, electronic structure, and catalytic function.
- Published
- 2014
44. Evaluating the electronic structure of formal Ln
- Author
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Megan E, Fieser, Maryline G, Ferrier, Jing, Su, Enrique, Batista, Samantha K, Cary, Jonathan W, Engle, William J, Evans, Juan S, Lezama Pacheco, Stosh A, Kozimor, Angela C, Olson, Austin J, Ryan, Benjamin W, Stein, Gregory L, Wagner, David H, Woen, Tonya, Vitova, and Ping, Yang
- Subjects
Chemistry - Abstract
LnII(C5H4SiMe3)1– have been characterized by XANES and DFT., The isolation of [K(2.2.2-cryptand)][Ln(C5H4SiMe3)3], formally containing LnII, for all lanthanides (excluding Pm) was surprising given that +2 oxidation states are typically regarded as inaccessible for most 4f-elements. Herein, X-ray absorption near-edge spectroscopy (XANES), ground-state density functional theory (DFT), and transition dipole moment calculations are used to investigate the possibility that Ln(C5H4SiMe3)3 1– (Ln = Pr, Nd, Sm, Gd, Tb, Dy, Y, Ho, Er, Tm, Yb and Lu) compounds represented molecular LnII complexes. Results from the ground-state DFT calculations were supported by additional calculations that utilized complete-active-space multi-configuration approach with second-order perturbation theoretical correction (CASPT2). Through comparisons with standards, Ln(C5H4SiMe3)3 1– (Ln = Sm, Tm, Yb, Lu, Y) are determined to contain 4f6 5d0 (SmII), 4f13 5d0 (TmII), 4f14 5d0 (YbII), 4f14 5d1 (LuII), and 4d1 (YII) electronic configurations. Additionally, our results suggest that Ln(C5H4SiMe3)3 1– (Ln = Pr, Nd, Gd, Tb, Dy, Ho, and Er) also contain LnII ions, but with 4fn 5d1 configurations (not 4fn+1 5d0). In these 4fn 5d1 complexes, the C 3h-symmetric ligand environment provides a highly shielded 5d-orbital of a′ symmetry that made the 4fn 5d1 electronic configurations lower in energy than the more typical 4fn+1 5d0 configuration.
- Published
- 2017
45. Proton Beam Production of Curie Scale Ac-225 at 100 MeV and Below
- Author
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C. Vermeulen, Christopher A. Martinez, Benjamin W. Stein, Meiring Nortier Nortier, Ellen M. O'Brien, Kevin D. John, Rishi Bhandia, Jason C. Cooley, Eric Olivas, and Eva R. Birnbaum
- Subjects
Nuclear physics ,Materials science ,Radiological and Ultrasound Technology ,Scale (ratio) ,Proton ,Curie ,Radiology, Nuclear Medicine and imaging ,Beam (structure) - Published
- 2019
46. Coordination Chemistry of +3 Actinium
- Author
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Kevin D. John, Benjamin W. Stein, Amanda Morgenstern, Laura M. Lilley, Veronika Mocko, Enrique R. Batista, Stosh A. Kozimor, and Eva R. Birnbaum
- Subjects
chemistry.chemical_classification ,Actinium ,Radiological and Ultrasound Technology ,chemistry ,Computational chemistry ,chemistry.chemical_element ,Radiology, Nuclear Medicine and imaging ,Coordination complex - Published
- 2019
47. Electronic and Exchange Coupling in a Cross-Conjugated D–B–A Biradical: Mechanistic Implications for Quantum Interference Effects
- Author
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Daniel E. Stasiw, David A. Shultz, Diana Habel-Rodriguez, Benjamin W. Stein, Martin L. Kirk, and Paul D. Boyle
- Subjects
Absorption spectroscopy ,Chemistry ,Context (language use) ,General Chemistry ,Electronic structure ,Photochemistry ,Biochemistry ,Catalysis ,law.invention ,Colloid and Surface Chemistry ,Chemical physics ,law ,Excited state ,Molecule ,Singlet state ,Physics::Chemical Physics ,Ground state ,Electron paramagnetic resonance - Abstract
A combination of variable-temperature EPR spectroscopy, electronic absorption spectroscopy, and magnetic susceptibility measurements have been performed on Tp(Cum,Me)Zn(SQ-m-Ph-NN) (1-meta) a donor-bridge-acceptor (D-B-A) biradical that possesses a cross-conjugated meta-phenylene (m-Ph) bridge and a spin singlet ground state. The experimental results have been interpreted in the context of detailed bonding and excited-state computations in order to understand the excited-state electronic structure of 1-meta. The results reveal important excited-state contributions to the ground-state singlet-triplet splitting in this cross-conjugated D-B-A biradical that contribute to our understanding of electronic coupling in cross-conjugated molecules and specifically to quantum interference effects. In contrast to the conjugated isomer, which is a D-B-A biradical possessing a para-phenylene bridge, admixture of a single low-lying singly excited D → A type configuration into the cross-conjugated D-B-A biradical ground state makes a negligible contribution to the ground-state magnetic exchange interaction. Instead, an excited state formed by a Ph-NN (HOMO) → Ph-NN (LUMO) one-electron promotion configurationally mixes into the ground state of the m-Ph bridged D-A biradical. This results in a double (dynamic) spin polarization mechanism as the dominant contributor to ground-state antiferromagnetic exchange coupling between the SQ and NN spins. Thus, the dominant exchange mechanism is one that activates the bridge moiety via the spin polarization of a doubly occupied orbital with phenylene bridge character. This mechanism is important, as it enhances the electronic and magnetic communication in cross-conjugated D-B-A molecules where, in the case of 1-meta, the magnetic exchange in the active electron approximation is expected to be J ~ 0 cm(-1). We hypothesize that similar superexchange mechanisms are common to all cross-conjugated D-B-A triads. Our results are compared to quantum interference effects on electron transfer/transport when cross-conjugated molecules are employed as the bridge or molecular wire component and suggest a mechanism by which electronic coupling (and therefore electron transfer/transport) can be modulated.
- Published
- 2013
48. Metal Complexes (M = Zn, Sn, and Pb) of 2-Phosphinobenzenethiolates: Insights into Ligand Folding and Hemilability
- Author
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Richard A. Kemp, Christopher A. Larsen, Benjamin W. Stein, Rory Waterman, Melissa N. Wirtz, William E. Geiger, and Brian Barry
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Inorganic Chemistry ,Folding (chemistry) ,Metal ,Crystallography ,Hemilability ,Chemistry ,Ligand ,visual_art ,visual_art.visual_art_medium ,Physical and Theoretical Chemistry ,Divalent metal - Abstract
The divalent metal complexes M(II){(SC6H4-2-PR2)-κ(2)S,P}2 (3-7, and 9-11) (M = Zn, Sn, or Pb; R = (i)Pr, (t)Bu, or Ph), the Sn(IV) complexes Sn{(SC6H4-2-PR2)-κ(2)-S,P}Ph2Cl (12 and 13) (R = (i)Pr and (t)Bu), and the ionic Sn(IV) complexes [Sn{(SC6H4-2-PR2)-κ(2)-S,P}Ph2][BPh4] (14 and 15) (R = (i)Pr and (t)Bu) have been prepared and characterized by multinuclear NMR spectroscopy and single crystal X-ray diffraction when suitable crystals were afforded. The Sn(II) and Pb(II) complexes with R = Ph, (i)Pr, or (t)Bu (5, 6, 9, and 10) demonstrated ligand "folding" hinging on the P,S vector-a behavior driven by the repulsions of the metal/phosphorus and metal/sulfur lone pairs and increased M-S sigma bonding strength. This phenomenon was examined by density functional theory (DFT) calculations for the compounds in both folded and unfolded states. The Sn(IV) compound 13 (R = (t)Bu) crystallized with the phosphine in an axial position of the pseudotrigonal bipyramidal complex and also exhibited hemilability in the Sn-P dative bond, while compound 12 (R = (i)Pr), interestingly, crystallized with phosphine in an equatorial position and did not show hemilability. Finally, the crystal structure of 15 (R = (t)Bu) revealed the presence of an uncommon, 4-coordinate, stable Sn(IV) cation.
- Published
- 2013
49. Comparing the 2,2'-Biphenylenedithiophosphinate Binding of Americium with Neodymium and Europium
- Author
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Joseph A. Macor, Justin N. Cross, David K. Shuh, Gregory S. Girolami, Benjamin W. Stein, Jeffery A. Bertke, Joel R. Maassen, S. Chantal E. Stieber, Maryline G. Ferrier, Brian L. Scott, and Stosh A. Kozimor
- Subjects
Lanthanide ,Ionic radius ,010405 organic chemistry ,Inorganic chemistry ,chemistry.chemical_element ,Americium ,General Chemistry ,Actinide ,010402 general chemistry ,01 natural sciences ,Neodymium ,Catalysis ,0104 chemical sciences ,Bond length ,Crystallography ,chemistry ,X-ray crystallography ,Europium - Abstract
Advancing our understanding of the minor actinides (Am, Cm) versus lanthanides is key for developing advanced nuclear-fuel cycles. Herein, we describe the preparation of (NBu4 )Am[S2 P((t) Bu2 C12 H6 )]4 and two isomorphous lanthanide complexes, namely one with a similar ionic radius (i.e., Nd(III) ) and an isoelectronic one (Eu(III) ). The results include the first measurement of an Am-S bond length, with a mean value of 2.921(9) A, by single-crystal X-ray diffraction. Comparison with the Eu(III) and Nd(III) complexes revealed subtle electronic differences between the complexes of Am(III) and the lanthanides.
- Published
- 2016
50. Spectroscopic and computational investigation of actinium coordination chemistry
- Author
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Henry S. La Pierre, Eva R. Birnbaum, Justin N. Cross, Enrique R. Batista, S. Chantal E. Stieber, Juan S. Lezama Pacheco, Justin J. Wilson, Maryline G. Ferrier, Jonathan W. Engle, Stosh A. Kozimor, John M. Berg, and Benjamin W. Stein
- Subjects
Lanthanide ,Actinium ,Models, Molecular ,Absorption spectroscopy ,Science ,General Physics and Astronomy ,chemistry.chemical_element ,010402 general chemistry ,01 natural sciences ,General Biochemistry, Genetics and Molecular Biology ,Coordination complex ,Reactivity (chemistry) ,chemistry.chemical_classification ,Radioisotopes ,X-ray absorption spectroscopy ,Multidisciplinary ,Fourier Analysis ,010405 organic chemistry ,General Chemistry ,Actinide ,3. Good health ,0104 chemical sciences ,Solutions ,X-Ray Absorption Spectroscopy ,chemistry ,Physical chemistry ,Density functional theory - Abstract
Actinium-225 is a promising isotope for targeted-α therapy. Unfortunately, progress in developing chelators for medicinal applications has been hindered by a limited understanding of actinium chemistry. This knowledge gap is primarily associated with handling actinium, as it is highly radioactive and in short supply. Hence, AcIII reactivity is often inferred from the lanthanides and minor actinides (that is, Am, Cm), with limited success. Here we overcome these challenges and characterize actinium in HCl solutions using X-ray absorption spectroscopy and molecular dynamics density functional theory. The Ac–Cl and Ac − O H 2 O distances are measured to be 2.95(3) and 2.59(3) Å, respectively. The X-ray absorption spectroscopy comparisons between AcIII and AmIII in HCl solutions indicate AcIII coordinates more inner-sphere Cl1– ligands (3.2±1.1) than AmIII (0.8±0.3). These results imply diverse reactivity for the +3 actinides and highlight the unexpected and unique AcIII chemical behaviour.
- Published
- 2016
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