A5009206599- X-ray Diffraction in Crystallography
- Crystallization and Solubility Studies
- CO2 Reduction Techniques and Catalysts
- Electrocatalysts for Energy Conversion
- Metalloenzymes and iron-sulfur proteins
- Metal-Catalyzed Oxygenation Mechanisms
- Ammonia Synthesis and Nitrogen Reduction
- Metal complexes synthesis and properties
- Catalytic Processes in Materials Science
- Perovskite Materials and Applications
- Catalytic C–H Functionalization Methods
- Carbon dioxide utilization in catalysis
- Organometallic Complex Synthesis and Catalysis
- Porphyrin and Phthalocyanine Chemistry
- Electrochemical Analysis and Applications
- Asymmetric Hydrogenation and Catalysis
- Lanthanide and Transition Metal Complexes
- Magnetism in coordination complexes
- Conducting polymers and applications
- Caching and Content Delivery
- Geochemistry and Geologic Mapping
- Photochemistry and Electron Transfer Studies
- Catalysis and Hydrodesulfurization Studies
- Mass Spectrometry Techniques and Applications
- Photochromic and Fluorescence Chemistry
University of North Carolina at Chapel Hill
2016-2023
Harvard University
2019-2022
Communities In Schools of Orange County
2020
Harvard University Press
2019
Oakland University
2013-2016
Brookhaven National Laboratory
2014
The need for benchmarking hydrogen evolution catalysts has increasingly been recognized. influence of acid choice on activity is often reduced to the overpotential catalysis. Through study a stable cobalt hydride complex, we demonstrate choice, beyond pKa, kinetics formation. A linear free energy relationship between pKa and second-order rate constants observed weaker acids. For stronger acids, however, further increases in do not correlate constants. Further, steric bulk around acidic...
We describe a new strategy for enhancing the efficiency of electrocatalytic CO2 reduction with homogeneous catalyst, using room-temperature ionic liquid as both solvent and electrolyte. The electrochemical behavior fac-ReCl(2,2′-bipyridine)(CO)3 in neat 1-ethyl-3-methylimidazolium tetracyanoborate ([emim][TCB]) was compared that acetonitrile containing 0.1 M [Bu4N][PF6]. Two separate one-electron reductions occur (−1.74 −2.11 V vs Fc+/0), modest catalytic current appearing at second wave...
Excited-state proton-coupled electron transfer (ES-PCET) is a promising avenue for solar fuel production and small molecule activation. Although less known about ES-PCET reactions than related transformations involving exclusively thermal processes, holds promise as simple efficient reaction scheme the formation of fuels, it may provide access to new reactivity not accessible from ground electronic states. This review classifies into six categories based on identity photoexcited reactant:...
Two-electron, one-proton reactions of a family [CoCp(dxpe)(NCCH3)]2+ complexes (Cp = cyclopentadienyl, dxpe 1,2-bis(di(aryl/alkyl)phosphino)ethane) form the corresponding hydride species [HCoCp(dxpe)]+ (dxpe dppe (1,2-bis(diphenylphosphino)ethane), depe (1,2-bis(diethylphosphino)ethane), and dcpe (1,2-bis(dicyclohexylphosphino)ethane)) through stepwise proton-coupled electron transfer process. For three complexes, peak shift analysis was employed to quantify apparent proton rate constants...
A series of rhenium diimine carbonyl complexes was prepared and characterized in order to examine the influence axial ligands on electronic structure. Systematic substitution acetonitrile [Re(deeb)(CO)3(NCCH3)]+ (deeb = 4,4′-diethylester-2,2′-bipyridine) with trimethylphosphine chloride, respectively, gives rise red-shifted absorbance features. These bathochromic shifts result from destabilization occupied d-orbitals involved metal-to-ligand charge-transfer transitions. Time-Dependent...
Artificial photosynthesis relies on coupling light absorption with chemical fuel generation. A mechanistic study of visible light-driven H2 production from [Cp*Ir(bpy)H]+ (1) has revealed a new, highly efficient pathway for integrating bond formation. The net reaction 1 proton source produces H2, but the rate excited state quenching is surprisingly acid-independent and displays no observable deuterium kinetic isotopic effect. Time-resolved photoluminescence labeling studies are consistent...
Halide mixing is one of the most powerful techniques to tune optical bandgap metal-halide perovskites. However, halide has commonly been observed result in phase segregation, which reduces excited-state transport and limits device performance. While current emphasis lies on development strategies prevent it remains unclear how may affect even if purity maintained. Here, we study exciton pure mixed-halide 2D perovskites (PEA)2Pb(I1–xBrx)4. Using transient photoluminescence microscopy, show...
Studying the formation of transition metal hydride complexes via proton-coupled electron transfer is important for developing next-generation molecular catalysts hydrogen evolution. We report herein study stepwise photoinduced reduction and protonation [CoIICp(dppe)]+ (Cp = cyclopentadienyl, dppe 1,2-bis(diphenylphosphino)ethane) to form corresponding complex [HCoIIICp(dppe)]+. Reaction intermediates were optically tracked using transient absorption spectroscopy, a combination experimental...
Molecules capable of both harvesting light and forming new chemical bonds hold promise for applications in the generation solar fuels, but such first-row transition metal photoelectrocatalysts are lacking. Here we report nickel H2 evolution, leveraging visible-light-driven photochemical evolution from bis(diphosphine)nickel hydride complexes. A suite experimental theoretical analyses, including time-resolved spectroscopy continuous irradiation quantum yield measurements, led to a proposed...
The innate H<sub>2</sub> evolution photochemistry of an iridium hydride complex is diverted towards photochemical hydrodechlorination dichloromethane with high selectivity and quantum yield.
Here we report electrochemical, spectroscopic, and crystallographic characterization of a redox series cobalt complexes in five sequential oxidation states. A simple bidentate phosphine ligand, cis-1,2-bis(diphenylphosphino)ethylene (dppv), allows for isolation the 3+, 2+, 1+, 0, 1- states cobalt─the only known example transition-metal with redox-innocent ligands Electrochemistry [Co(dppv)2]2+ reveals three reversible reductions one oxidation. Complexes each state are characterized using...
Ring currents in aryl phosphine ligands yield intra-ligand anisotropic shielding on the bipyridine protons of up to 0.59 ppm.
The characteristic red color of many natural tourmalines is due to the presence Mn(III) cations substituting for aluminum and lithium. These sites originate as Mn(II) are oxidized by γ-irradiation over geologic time they sit in Earth's crust. Presented here a thorough analysis spin-allowed spin-forbidden transitions which give rise these gemstones. Ligand field analysis, supplemented time-dependent density functional theory, was used correct historical assignments symmetry-allowed polarized...
As the utility of electroanalytical methods to study reaction mechanisms continues develop, a wider scope chemical reactions will fall under scrutiny electrochemical investigation. We report herein thermochemical and electrosynthetic routes stable rhenium hydride complexes ReClCp(H)(dppx) (dppx = 1,1-bis(diphenylphosphino)methane (dppm), 1,2-bis(diphenylphosphino)ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp), Cp cyclopentadienyl). These are accessed via reduction corresponding...
We report the isolation and characterization of a series three cobalt(II) bis(phosphine) complexes with varying numbers coordinated solvent ligands in axial position. X-ray quality crystals [Co(dppv)2][BF4]2(1), [Co(dppv)2(NCCH3)][BPh4]2(2), [Co(dppv)2(NCCH3)2][BF4]2(3) (dppv = cis-1,2-bis(diphenylphosphino)ethylene) were grown under slightly different conditions, their structures compared. This analysis revealed multiple crystallization motifs for divalent same set phosphine ligands....