A5057261669- X-ray Diffraction in Crystallography
- Crystallization and Solubility Studies
- Metal-Catalyzed Oxygenation Mechanisms
- Radioactive element chemistry and processing
- Catalytic Processes in Materials Science
- Machine Learning in Materials Science
- CO2 Reduction Techniques and Catalysts
- Metal complexes synthesis and properties
- X-ray Spectroscopy and Fluorescence Analysis
- Computational Drug Discovery Methods
- Porphyrin Metabolism and Disorders
- Electrochemical Analysis and Applications
- Synthesis and Reactions of Organic Compounds
- Fluorine in Organic Chemistry
- Electron and X-Ray Spectroscopy Techniques
- Electrochemical sensors and biosensors
- Magnetism in coordination complexes
- Catalysis and Oxidation Reactions
- Enzyme Structure and Function
- Advancements in Battery Materials
- Microfluidic and Capillary Electrophoresis Applications
- Metalloenzymes and iron-sulfur proteins
- Lanthanide and Transition Metal Complexes
- Synthesis and Biological Evaluation
- Carbon dioxide utilization in catalysis
Stanford University
2018-2025
SLAC National Accelerator Laboratory
2022-2025
Stanford Synchrotron Radiation Lightsource
2022-2025
Lawrence Berkeley National Laboratory
2017-2020
Berkeley College
2020
École Polytechnique
2017
Centre National de la Recherche Scientifique
2017
Université Paris-Saclay
2017
Harvard University
2016
High-valent ferryl species (e.g., (Por)Fe
The direct conversion of methane to methanol would have a wide reaching environmental and industrial impact. Copper-containing zeolites can perform this reaction at low temperatures pressures previously defined O
Fe K-edge X-ray absorption spectroscopy (XAS) has long been used for the study of high-valent iron intermediates in biological and artificial catalysts. 4p-mixing into 3d orbitals complicates pre-edge analysis but when correctly understood via 1s2p resonant inelastic scattering L-edge XAS, it enables deeper insight geometric structure correlates with electronic reactivity. This shows that addition to 3dz2 orbital due short iron–oxo bond, loss inversion equatorial plane leads 4p mixing...
In multicopper oxidases (MCOs), the type 1 (T1) Cu accepts electrons from substrate and transfers these to trinuclear cluster (TNC) where O2 is reduced H2O. The T1 potential in MCOs varies 340 780 mV, a range not explained by existing literature. This study focused on ∼350 mV difference of center Fet3p Trametes versicolor laccase (TvL) that have same 2His1Cys ligand set. A spectroscopies performed oxidized sites shows they equivalent geometric electronic structures. However, two His ligands...
A general method for the synthesis of [(18) F]difluoromethylarenes from F]fluoride radiopharmaceutical discovery is reported. The practical, operationally simple, tolerates a wide scope functional groups, and enables labeling variety arenes heteroarenes with radiochemical yields (RCYs, not decay-corrected) 10 to 60 %. (18) F-fluorination precursors are readily prepared aryl chlorides, bromides, iodides, triflates. Seven F-difluoromethylarene drug analogues radiopharmaceuticals including...
Offline recognition of hand-drawn hydrocarbon structures is learned using an image-to-SMILES neural network through the application synthetic data generation and ensemble learning.
Methanotrophic bacteria utilize the nonheme diiron enzyme soluble methane monooxygenase (sMMO) to convert methanol in first step of their metabolic cycle under copper-limiting conditions. The structure sMMO Fe(IV)2 intermediate Q responsible for activating inert C–H bond (BDE = 104 kcal/mol) remains controversial, with recent studies suggesting both "open" and "closed" core geometries its active site. In this study, we employ nuclear resonance vibrational spectroscopy (NRVS) probe geometric...
High-valent Fe IV =O species are common intermediates in biological and artificial catalysts. Heme nonheme S=1 sites have been synthesized studied for decades but little quantitative experimental comparison of their electronic structures has available, due to the lack direct methods focused on iron. This study allows a rigorous determination structure center its an heme site using 1s2p resonant inelastic X-ray scattering (RIXS) L-edge absorption spectroscopy (XAS). Further, variable...
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.
Methane is one of the most potent greenhouse gases; developing technology for its abatement essential combating climate change. Copper zeolites can activate methane at low temperatures and pressures, demonstrating promise this technology. However, a barrier to industrial implementation inability recycle Cu(II) active site. Anaerobic site regeneration has been reported copper-loaded mordenite, where it proposed that water oxidizes Cu(I) formed from reaction, producing H2 gas as byproduct....
The base-free divalent samarium complex Cptt2Sm (1; Cptt = 1,3-(tBu)2(C5H3)) has been synthesized in diethyl ether by salt metathesis of SmI2. Crystals 1 suitable for X-ray study have obtained sublimation at 116 °C under reduced pressure. dissolution thf and pyridine solution leads to the solvent adducts Cptt2Sm(thf)2 (3) Cptt2Sm(py) (4), respectively, while drying 3 pressure yields CpttSm(thf) (5). reaction CO2 with complexes (1) Cpttt2Sm (2; Cpttt =1,2,4-(tBu)3(C5H2)) clean formation...
Significance Fe zeolites are heterogeneous catalysts that show potential in a number of important industrial applications, including the selective partial oxidation methane to methanol at room temperature, and conversion benzene phenol. There practical limitations associated with Fe-zeolite may be resolved mechanistic insight; however, reliable experimental data on limited. This study defines mechanism hydroxylation catalyzed by zeolites, clarifying relationship between active site structure...
1s2p resonant inelastic X-ray scattering (1s2p RIXS) has proven successful in the determination of differential orbital covalency (DOC, amount metal vs ligand character each d molecular orbital) highly covalent centrosymmetric iron environments including heme models and enzymes. However, many reactive intermediates have noncentrosymmetric environments, e.g., presence strong metal-oxo bonds, which results mixing 4p into 3d orbitals. This leads to significant intensity enhancement K-pre-edge...
Kβ X-ray emission spectroscopy (XES) is widely used to fingerprint the local spin of transition-metal ions, including in pump–probe experiments, identify excited states or chemical and biological reactions characterize short-lived intermediates. In this study, spectra ferrous ferric complexes for various were measured experimentally described theoretically through restricted active space (RAS) calculations dynamic correlations. Through RAS from simple atomic models complex molecular systems,...
Inputting molecules into chemistry software, such as quantum packages, currently requires domain expertise, expensive software and/or cumbersome procedures. Leveraging recent breakthroughs in machine learning, we develop ChemPix: an offline, hand-drawn hydrocarbon structure recognition tool designed to remove these barriers. A neural image captioning approach consisting of a convolutional network (CNN) encoder and long short-term memory (LSTM) decoder learned mapping from photographs...
Oxygen and aluminum K-edge X-ray absorption spectroscopy (XAS), imaging from a scanning transmission microscope (STXM), first-principles calculations were used to probe the composition morphology of bulk metal, α- γ-Al2O3, several types nanoparticles. The results agreed with earlier electron microscopy studies that showed 2 5 nm thick layer Al2O3 on all Al surfaces. Spectral interpretations guided by examination calculated transition energies, which well spectroscopic measurements. Features...
Iron is the most abundant transition metal in Earth’s crust, and redox cycling between its well-known low-valent oxidation states of FeII FeIII drives crucial processes nature. The FeII/III couple charge compensates lithium iron phosphate, a positive electrode (cathode) for lithium-ion batteries. High-valent couples, involving formal higher than FeIII, could deliver electrochemical potentials energy densities. However, because instability high-valent Fe electrodes, they have proven difficult...
Iron(IV)-oxo intermediates found in iron enzymes and artificial catalysts are competent for H atom abstraction catalytic cycles. For S = 2 intermediates, both axial equatorial approaches well-established. The mechanism 1 sites is not as well understood: an approach more energetically favorable, requires crossing from the to surface. In this study, we use 1s2p resonant inelastic X-ray scattering (RIXS) Fe L-edge absorption spectroscopy on [FeIVO(TMC)(CH3CN)]2+ observe final states, which...
Abstract A general method for the synthesis of [ 18 F]difluoromethylarenes from F]fluoride radiopharmaceutical discovery is reported. The practical, operationally simple, tolerates a wide scope functional groups, and enables labeling variety arenes heteroarenes with radiochemical yields (RCYs, not decay‐corrected) 10 to 60 %. F‐fluorination precursors are readily prepared aryl chlorides, bromides, iodides, triflates. Seven F‐difluoromethylarene drug analogues radiopharmaceuticals including...
Determination of electronic structures during chemical reactions remains challenging in studies which involve the millisecond timescale, toxic chemicals, and/or anaerobic conditions. In this study, a three-dimensionally (3D) microfabricated microfluidic mixer platform that is compatible with time-resolved X-ray absorption and emission spectroscopy (XAS XES, respectively) presented. This platform, to initiate study their progression, mixes high flow rate (0.50-1.5 ml min-1) sheath stream...
The overwhelming majority of layered oxide cathode materials are based on the redox activity expensive and scarce transition metals like Co Ni. While Fe-redox material LiFePO 4 has become increasingly attractive due to its low cost, gravimetric energy density relatively operating voltage limit use cases. A high-voltage Fe-based would provide high utilizing redox-activity most abundant metal in Earth’s crust, but such a that provides stable reversible electrochemical performance remains...
Abstract The activation of inert C( sp 3 )-H bonds by non-heme Fe enzymes plays a key role in metabolism, epigenetics, and signaling, while providing powerful biocatalytic platform for the chemical synthesis molecules with increased complexity. In this context, II /α-ketoglutarate-dependent radical halogenases represent broadly interesting system, as they are uniquely capable carrying out transfer diverse array bound anions following C-H activation. Here, we provide first experimental...
Anionic redox is defined as the depopulation of electronic states consisting unhybridized or minimally hybridized O 2 p orbitals. In recent years, anionic has been investigated in great detail due its potential to increase high-voltage capacity Na-ion and Li-ion intercalation positive electrodes (cathodes) for batteries. However, almost always manifests alongside a gamut undesirable effects, from > 1 V hysteresis, voltage fade over hundreds cycles. These effects have hindered widespread...
<p>Inputting molecules into chemistry software, such as quantum packages, currently requires domain expertise, expensive software and/or cumbersome procedures. Leveraging recent breakthroughs in machine learning, we develop ChemPix: an offline, hand-drawn hydrocarbon structure recognition tool designed to remove these barriers. A neural image captioning approach consisting of a convolutional network (CNN) encoder and long short-term memory (LSTM) decoder learned mapping from...