A5014705001- Crystallization and Solubility Studies
- X-ray Diffraction in Crystallography
- Metal-Catalyzed Oxygenation Mechanisms
- Radioactive element chemistry and processing
- Metalloenzymes and iron-sulfur proteins
- Radiopharmaceutical Chemistry and Applications
- Lanthanide and Transition Metal Complexes
- Metal complexes synthesis and properties
- Magnetism in coordination complexes
- Monoclonal and Polyclonal Antibodies Research
- Electrocatalysts for Energy Conversion
- HER2/EGFR in Cancer Research
- Organometallic Complex Synthesis and Catalysis
- Electrochemical Analysis and Applications
- Chemical Synthesis and Characterization
- X-ray Spectroscopy and Fluorescence Analysis
- Enzyme Structure and Function
- MRI in cancer diagnosis
- Intelligent Tutoring Systems and Adaptive Learning
- Microbial Fuel Cells and Bioremediation
- Cultural Identity and Heritage
- Nuclear materials and radiation effects
- Catalytic Processes in Materials Science
- CO2 Reduction Techniques and Catalysts
- ATP Synthase and ATPases Research
Lawrence Berkeley National Laboratory
2018-2022
University of Washington
2015-2021
Berkeley College
2020
Max Planck Institute for Chemical Energy Conversion
2015-2017
Ruhr West University of Applied Sciences
2017
Iron porphyrins can act as potent electrocatalysts for CO2 functionalization. The catalytically active species has been proposed to be a formal Fe(0) porphyrin complex, [Fe(TPP)]2- (TPP = tetraphenylporphyrin), generated by two-electron reduction of [FeII(TPP)]. Our combined spectroscopic and computational investigations reveal that the is ligand-centered best formulated an intermediate-spin Fe(II) center antiferromagnetically coupled diradical anion, yielding overall singlet ground state....
Abstract The first direct evidence is provided for the presence of an interstitial carbide in FeV cofactor Azotobacter vinelandii vanadium nitrogenase. As our identification central FeMo cofactor, we employed Fe Kβ valence‐to‐core X‐ray emission spectroscopy and density functional theory calculations, herein report highly similar spectra both variants cofactor‐containing protein. analogous carbide, thus atomically homologous active site nitrogenase, highlights importance influence identity...
Use of a macrocyclic tetracarbene ligand, which is topologically reminiscent tetrapyrrole macrocycles though electronically distinct, has allowed for the isolation, X-ray crystallographic characterization and comprehensive spectroscopic investigation complete set {FeNO}x complexes (x = 6, 7, 8). Electrochemical reduction, or chemical reduction with CoCp2, {FeNO}7 complex 1 leads to organometallic {FeNO}8 species 2. Its structure determination first nonheme iron nitroxyl identify structural...
High-resolution X-ray spectroscopy provides insights into the electronic structural differences between nitrogenase FeMoco and FeVco clusters.
Abstract Several MRI contrast agent clinical formulations are now known to leave deposits of the heavy metal gadolinium in brain, bones, and other organs patients. This persistent biological accumulation has been recently recognized as a deleterious outcome patients administered Gd-based agents (GBCAs) for MRI, prompting European Medicines Agency recommend discontinuing use over half GBCAs currently approved applications. To address this problem, we find that orally-available decorporation...
Manganese K-edge X-ray absorption (XAS) and Kβ emission (XES) spectroscopies were used to investigate the factors contributing O–O bond activation in a small-molecule system. The recent structural characterization of metastable peroxo-bridged dimeric Mn(III)2 complex derived from dioxygen has provided first opportunity obtain spectroscopic data on this type species. Ground state time-dependent density functional theory calculations have further insight into nature transitions XAS pre-edge...
Abstract The bioinorganic chemistry community has had a long history of utilizing diverse range spectroscopic techniques to obtain detailed geometric and electronic structural insights into metalloprotein active sites. In recent years, the development beamlines optimized for high‐resolution X‐ray spectroscopy provided novel tools elucidation biological site structures. These methods include both non‐resonant resonant emission spectroscopy. Herein, we briefly introduce absorption...
Abstract The formation of the high‐valent iron complex [Fe(cyclohexyl) 4 ] from Fe II under reducing conditions is best explained by disproportionation a transient organoiron intermediate which driven dispersive forces between cyclohexyl ligands and short strong Fe−C bonds. (meta)stability this diamagnetic (S=0) striking if one considers that it has empty d‐orbitals at its disposal contains, same time, no less than twenty H‐atoms available for either α‐ or β‐hydride elimination.
A series of vanadium compounds was studied by K-edge X-ray absorption (XAS) and K $$\beta $$ emission spectroscopies (XES). Qualitative trends within the datasets, as well comparisons between XAS XES data, illustrate information content both methods. The complementary nature chemical insight highlights success this dual-technique approach in characterizing structural electronic properties sites. In particular, contrast to or extended fine structure (EXAFS), we demonstrate that...
Herein, a systematic study of series molecular iron model complexes has been carried out using Fe L2,3-edge X-ray absorption (XAS) and magnetic circular dichroism (XMCD) spectroscopies. This spans increasing complexity, starting from ferric ferrous tetrachlorides ([FeCl4]−/2–), to tetrathiolates ([Fe(SR)4]−/2–), diferric mixed-valent iron–sulfur [Fe2S2R4]2–/3–. test set compounds is used evaluate the sensitivity both XAS XMCD spectroscopy oxidation state ligation changes. It demonstrated...
ThO<sub>2</sub> and UO<sub>2</sub> nanoparticles synthesized using a COF-5 template exhibit unpassivated surfaces provide insight into nanoscale properties of actinides.
Cysteinate oxygenation is intimately tied to the function of both cysteine dioxygenases (CDOs) and nitrile hydratases (NHases), yet mechanisms by which sulfurs are oxidized these enzymes unknown, in part because intermediates have be observed. Herein, we report a five-coordinate bis-thiolate ligated Fe(III) complex, [FeIII(S2Me2N3(Pr,Pr))]+ (2), that reacts with oxo atom donors (PhIO, IBX-ester, H2O2) afford rare example singly oxygenated sulfenate, [FeIII(η2-SMe2O)(SMe2)N3(Pr,Pr)]+ (5),...
Interest in the use of 225Ac for targeted alpha therapies has increased dramatically over past few years, resulting a multitude new isotope production and translational research efforts. However, radioimmunoconjugate (RIC) is still its infancy, with most prior experience hematologic malignancies only one reported preclinical solid tumor study using RICs. In an effort to compare RICs other current antibody conjugates, variety are tested against intractable small-cell lung cancer (SCLC). We...
Herein we quantitatively investigate how metal ion Lewis acidity and steric properties influence the kinetics thermodynamics of dioxygen binding versus release from structurally analogous Mn–O2 complexes, as well barrier to Mn peroxo O–O bond cleavage, reactivity oxo intermediates. Previously demonstrated that electronic MnIII–OOR complexes containing N-heterocyclic (NAr) ligand scaffolds can have a dramatic on alkylperoxo lengths cleavage. Herein, examine new MnII complex more...
Abstract The formation of the high‐valent iron complex [Fe(cyclohexyl) 4 ] from Fe II under reducing conditions is best explained by disproportionation a transient organoiron intermediate which driven dispersive forces between cyclohexyl ligands and short strong Fe−C bonds. (meta)stability this diamagnetic (S=0) striking if one considers that it has empty d‐orbitals at its disposal contains, same time, no less than twenty H‐atoms available for either α‐ or β‐hydride elimination.
The solution-state interactions between octadentate hydroxypyridinone (HOPO) and catecholamide (CAM) chelating ligands uranium were investigated characterized by UV–visible spectrophotometry X-ray absorption spectroscopy (XAS), as well electrochemically via spectroelectrochemistry (SEC) cyclic voltammetry (CV) measurements. Depending on the selected chelator, we demonstrate controlled ability to bind stabilize UIV, generating with 3,4,3-LI(1,2-HOPO), a tetravalent complex that is practically...
Octadentate hydroxypyridinone (HOPO) and catecholamide (CAM) siderophore analogues are known to be efficacious chelators of the actinide cations, these ligands also capable facilitating both activation reduction actinyl species. Utilizing X-ray absorption near edge structure (XANES) extended fine (EXAFS) spectroscopies, as well cyclic voltammetry measurements, herein, we elucidate chelation-based mechanisms for driving reactivity initiating redox processes in a family neptunyl-HOPO CAM...
Abstract The first direct evidence is provided for the presence of an interstitial carbide in FeV cofactor Azotobacter vinelandii vanadium nitrogenase. As our identification central FeMo cofactor, we employed Fe Kβ valence‐to‐core X‐ray emission spectroscopy and density functional theory calculations, herein report highly similar spectra both variants cofactor‐containing protein. analogous carbide, thus atomically homologous active site nitrogenase, highlights importance influence identity...
Abstract An ideal chelator for f‐elements features rapid kinetics of complexation, high thermodynamic stability, and slow dissociation. Here we present the facile synthesis a macrocyclic ligand bearing four 1‐hydroxy‐2‐pyridinone units linked to cyclen scaffold that rapidly forms thermodynamically stable complexes with lanthanides (Sm 3+ , Eu Tb Dy ) representative late actinide (Cm in aqueous media concurrently sensitizes them. Extended X‐ray absorption fine structure (EXAFS) spectroscopy...
Considerable effort has been devoted to the development of first-row transition-metal catalysts containing redox-active imino-pyridine ligands that are capable storing multiple reducing equivalents. This property allows abundant and inexpensive transition metals, which favor sequential one-electron redox processes, function as competent in concerted two-electron reduction substrates. Herein we report syntheses characterization a series iron complexes contain both π-donating thiolate...
The solution-state interactions of plutonium and berkelium with the octadentate chelator 3,4,3-LI(1,2-HOPO) (343-HOPO) were investigated characterized by X-ray absorption spectroscopy, which revealed in situ reductive decomposition tetravalent species both actinide metals to yield Pu(III) Bk(III) coordination complexes. near-edge structure (XANES) measurements first indication synchrotron redox chemistry as Pu threshold white-line position energies for Pu-343-HOPO good agreement known...