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Articles 1 - 30 of 44
Full-Text Articles in Chemistry
Unveiling Charge-Separation Dynamics In Cds/Metal–Organic Framework Composites For Enhanced Photocatalysis, Hai-Qun Xu, Sizhuo Yang, Xing Ma, Jier Huang, Hai-Long Wang
Unveiling Charge-Separation Dynamics In Cds/Metal–Organic Framework Composites For Enhanced Photocatalysis, Hai-Qun Xu, Sizhuo Yang, Xing Ma, Jier Huang, Hai-Long Wang
Chemistry Faculty Research and Publications
Photocatalytic water splitting for H2 production becomes one of the most favorable pathways for solar energy utilization, while the charge-separation dynamics in composite photocatalysts is largely elusive. In the present work, CdS-decorated metal–organic framework (MOF) composites, namely, CdS/UiO-66, have been synthesized and exhibit high H2 production activity from photocatalytic water splitting, far surpassing the MOF and CdS counterparts, under visible light irradiation. Transient absorption (TA) spectroscopy has been adopted in this report to unveil the charge-separation dynamics in CdS/UiO-66 composites, a key process that dictates their function in photocatalysis. We show that, in addition to the preferable formation …
Erratum: “Several Levels Of Theory For Description Of Isotope Effects In Ozone: Effect Of Resonance Lifetimes And Channel Couplings”, Alexander Teplukhin, Igor Gayday, Dmitri Babikov
Erratum: “Several Levels Of Theory For Description Of Isotope Effects In Ozone: Effect Of Resonance Lifetimes And Channel Couplings”, Alexander Teplukhin, Igor Gayday, Dmitri Babikov
Chemistry Faculty Research and Publications
No abstract provided.
Reactive Pathways In The Bromobenzene-Ammonia Dimer Cation Radical: Evidence For A Roaming Halogen Radical, Silver Nyambo, Brandon Uhler, Lloyd Godfrey Muzangwa, Maxim Vadimovich Ivanov, Bradley K. Welch, Richard Dawes, Scott A. Reid
Reactive Pathways In The Bromobenzene-Ammonia Dimer Cation Radical: Evidence For A Roaming Halogen Radical, Silver Nyambo, Brandon Uhler, Lloyd Godfrey Muzangwa, Maxim Vadimovich Ivanov, Bradley K. Welch, Richard Dawes, Scott A. Reid
Chemistry Faculty Research and Publications
Photoinitiated reactions in van der Waals complexes provide a means to examine reactive pathways from well-defined initial geometries. In recent work, we re-examined reactive pathways following resonant two-photon ionization (R2PI) of the chlorobenzene-ammonia (PhCl⋯NH3) dimer. The dimer cation radical reacts primarily via Cl atom loss, and additional channels corresponding to HCl and H atom loss were identified. The structure of the reactive complex was confirmed as an in-plane σ-type, and computational studies of the dimer cation radical potential energy landscape revealed two nearly isoenergetic arenium ion intermediates (or Wheland intermediates). The intermediate produced from ipso addition was not …
Several Levels Of Theory For Description Of Isotope Effects In Ozone: Effect Of Resonance Lifetimes And Channel Couplings, Alexander Teplukhin, Dmitri Babikov, Igor Gayday
Several Levels Of Theory For Description Of Isotope Effects In Ozone: Effect Of Resonance Lifetimes And Channel Couplings, Alexander Teplukhin, Dmitri Babikov, Igor Gayday
Chemistry Faculty Research and Publications
In this paper, two levels of theory are developed to determine the role of scattering resonances in the process of ozone formation. At the lower theory level, we compute resonance lifetimes in the simplest possible way, by neglecting all couplings between the diabatic vibrational channels in the problem. This permits to determine the effect of “shape” resonances, trapped behind the centrifugal barrier and populated by quantum tunneling. At the next level of theory, we include couplings between the vibrational channels, which permits to determine the role of Feshbach resonances and interaction of different reaction pathways on the global PES of …
Multielectron Redox Chemistry Of Transition Metal Complexes Supported By A Non‐Innocent N3p2 Ligand: Synthesis, Characterization, And Catalytic Properties, Denan Wang, Danushka M. Ekanayake, Sergey V. Lindeman, Cláudio N. Verani, Adam T. Fiedler
Multielectron Redox Chemistry Of Transition Metal Complexes Supported By A Non‐Innocent N3p2 Ligand: Synthesis, Characterization, And Catalytic Properties, Denan Wang, Danushka M. Ekanayake, Sergey V. Lindeman, Cláudio N. Verani, Adam T. Fiedler
Chemistry Faculty Research and Publications
A new redox‐active, diarylamido‐based ligand (LN3P2) capable of κ5‐N,N,N,P,P chelation has been used to prepare a series of complexes with the general formula [MII(LN3P2)]X, where M = Fe (1; X = OTf), Co (2; X = ClO4), or Ni (3; X = ClO4). The diarylamido core of monoanionic LN3P2 is derived from bis(2‐amino‐4‐methylphenyl)amine, which undergoes condensation with two equivalents of 2‐(diphenylphosphanyl)benzaldehyde to provide chelating arms with both arylphosphine and imine donors. X‐ray structural, magnetic, …
Dft-Assisted Design And Evaluation Of Bifunctional Amine/Pyridine-Oxazoline Metal Catalysts For Additions Of Ketones To Unactivated Alkenes And Alkynes, Eric Greve, Jacob D. Porter, Chris Dockendorff
Dft-Assisted Design And Evaluation Of Bifunctional Amine/Pyridine-Oxazoline Metal Catalysts For Additions Of Ketones To Unactivated Alkenes And Alkynes, Eric Greve, Jacob D. Porter, Chris Dockendorff
Chemistry Faculty Research and Publications
Bifunctional catalyst systems for the direct addition of ketones to unactivated alkenes/alkynes were designed and modeled by density functional theory (DFT). The designed catalysts possess bidentate ligands suitable for binding of pi-acidic group 10 metals capable of activating alkenes/alkynes, and a tethered organocatalyst amine to activate the ketone via formation of a nucleophilic enamine intermediate. The structures of the designed catalysts before and after C–C bond formation were optimized using DFT, and reaction steps involving group 10 metals were predicted to be significantly exergonic. A novel oxazoline precatalyst with a tethered amine separated by a meta-substituted benzene spacer was synthesized …
Π-Π Stacking Vs. C–H/Π Interaction: Excimer Formation And Charge Resonance Stabilization In Van Der Waals Clusters Of 9,9′-Dimethylfluorene, Damian Kokkin, Maxim Vadimovich Ivanov, John Loman, Sheng Cai, Brandon Uhler, Neil Reilly, Rajendra Rathore, Scott A. Reid
Π-Π Stacking Vs. C–H/Π Interaction: Excimer Formation And Charge Resonance Stabilization In Van Der Waals Clusters Of 9,9′-Dimethylfluorene, Damian Kokkin, Maxim Vadimovich Ivanov, John Loman, Sheng Cai, Brandon Uhler, Neil Reilly, Rajendra Rathore, Scott A. Reid
Chemistry Faculty Research and Publications
Studies of exciton and hole stabilization in multichromophoric systems underpin our understanding of electron transfer and transport in materials and biomolecules. The simplest model systems are dimeric, and recently we compared the gas-phase spectroscopy and dynamics of van der Waals dimers of fluorene, 9-methylfluorene (MF), and 9,9′-dimethylfluorene (F1) to assess how sterically controlled facial encumbrance modulates the dynamics of excimer formation and charge resonance stabilization (CRS). Dimers of fluorene and MF show only excimer emission upon electronic excitation, and significant CRS as evidenced in a reduced ionization potential for the dimer relative the monomer. By contrast, the dimer of F1 …
A Synthetic Model Of The Nonheme Iron–Superoxo Intermediate Of Cysteine Dioxygenase, Anne A. Fischer, Sergey V. Lindeman, Adam T. Fiedler
A Synthetic Model Of The Nonheme Iron–Superoxo Intermediate Of Cysteine Dioxygenase, Anne A. Fischer, Sergey V. Lindeman, Adam T. Fiedler
Chemistry Faculty Research and Publications
A nonheme Fe(II) complex (1) that models substrate-bound cysteine dioxygenase (CDO) reacts with O2 at −80 °C to yield a purple intermediate (2). Analysis with spectroscopic and computational methods determined that 2 features a thiolate-ligated Fe(III) center bound to a superoxide radical, mimicking the putative structure of a key CDO intermediate.
Dft-Assisted Design And Evaluation Of Bifunctional Copper(I) Catalysts For The Direct Intermolecular Addition Of Aldehydes And Ketones To Alkynes, Jacob D. Porter, Eric Greve, Abdulmohsen Alsafran, Adam R. Benoit, Sergey V. Lindeman, Chris Dockendorff
Dft-Assisted Design And Evaluation Of Bifunctional Copper(I) Catalysts For The Direct Intermolecular Addition Of Aldehydes And Ketones To Alkynes, Jacob D. Porter, Eric Greve, Abdulmohsen Alsafran, Adam R. Benoit, Sergey V. Lindeman, Chris Dockendorff
Chemistry Faculty Research and Publications
Bifunctional catalysts containing discrete metal pi-acid and amine sites were designed and investigated for the direct intermolecular addition of aldehydes and ketones to unactivated alkynes. Copper(I)-based catalysts were prioritized based on intramolecular (Conia-ene type) reactions, and complexes were designed with tridentate ligands and potentially hemilabile heterocyclic spacers. The structures of the designed catalysts were computed using density functional theory (DFT), and the relative energies of putative catalytic intermediates were estimated and used to prioritize catalyst designs. Novel bifunctional precatalysts containing a thiazole spacer were synthesized via a 9-step sequence and combined with transition metals before screening for the direct addition …
Synthesis And Evaluation Of 4-Cycloheptylphenols As Selective Estrogen Receptor-Β Agonists (Serbas), K. L. Iresha Sampathi Perera, Alicia M. Hanson, Sergey V. Lindeman, Andrea Imhoff, Xingyun Lu, Daniel S. Sem, William A. Donaldson
Synthesis And Evaluation Of 4-Cycloheptylphenols As Selective Estrogen Receptor-Β Agonists (Serbas), K. L. Iresha Sampathi Perera, Alicia M. Hanson, Sergey V. Lindeman, Andrea Imhoff, Xingyun Lu, Daniel S. Sem, William A. Donaldson
Chemistry Faculty Research and Publications
A short and efficient route to 4-(4-hydroxyphenyl)cycloheptanemethanol was developed, which resulted in the preparation of a mixture of 4 stereoisomers. The stereoisomers were separated by preparative HPLC, and two of the stereoisomers identified by X-ray crystallography. The stereoisomers, as well as a small family of 4-cycloheptylphenol derivatives, were evaluated as estrogen receptor-beta agonists. The lead compound, 4-(4-hydroxyphenyl)cycloheptanemethanol was selective for activating ER relative to seven other nuclear hormone receptors, with 300-fold selectivity for the β over α isoform and with EC50 of 30–50 nM in cell-based and direct binding assays.
Synthesis Of A Novel Bicyclic Scaffold Inspired By The Antifungal Natural Product Sordarin, Yibiao Wu, Chris Dockendorff
Synthesis Of A Novel Bicyclic Scaffold Inspired By The Antifungal Natural Product Sordarin, Yibiao Wu, Chris Dockendorff
Chemistry Faculty Research and Publications
A simplified bicyclic scaffold inspired by the antifungal natural product sordarin was designed and synthesized which maintains the carboxylic acid/aldehyde (or nitrile) pharmacophore. Docking studies with the target for sordarin, the fungal protein eukaryotic elongation factor 2 (eEF2), suggested that the novel scaffolds may bind productively. A densely functionalized chiral cyclopentadiene was constructed in 8 steps and utilized in a Diels-Alder reaction with acrylonitrile. The resulting [2.2.1] cycloheptene was transformed into a scaffold possessing vicinal carboxylic acid and nitrile groups, with orientations predicted to provide high affinity for eEF2. The synthetic approach disclosed here sets the stage for a renewed …
Vertical Vs. Adiabatic Ionization Energies In Solution And Gas-Phase: Probing Ionization-Induced Reorganization In Conformationally-Mobile Bichromophoric Actuators Using Photoelectron Spectroscopy, Electrochemistry And Theory, Maxim Vadimovich Ivanov, Denan Wang, Depeng Zhang, Rajendra Rathore, Scott A. Reid
Vertical Vs. Adiabatic Ionization Energies In Solution And Gas-Phase: Probing Ionization-Induced Reorganization In Conformationally-Mobile Bichromophoric Actuators Using Photoelectron Spectroscopy, Electrochemistry And Theory, Maxim Vadimovich Ivanov, Denan Wang, Depeng Zhang, Rajendra Rathore, Scott A. Reid
Chemistry Faculty Research and Publications
Ionization-induced structural and conformational reorganization in various π-stacked dimers and covalently linked bichromophores is relevant to many processes in biological systems and functional materials. In this work, we examine the role of structural, conformational, and solvent reorganization in a set of conformationally mobile bichromophoric donors, using a combination of gas-phase photoelectron spectroscopy, solution-phase electrochemistry, and density functional theory (DFT) calculations. Photoelectron spectral analysis yields both adiabatic and vertical ionization energies (AIE/VIE), which are compared with measured (adiabatic) solution-phase oxidation potentials (Eox). Importantly, we find a strong correlation of Eox with AIE, but not VIE, reflecting variations …
Spreading Electron Density Thin: Increasing The Chromophore Size In Polyaromatic Wires Decreases Interchromophoric Electronic Coupling, Mohammad Mosharraf Hossain, Maxim Vadimovich Ivanov, Denan Wang, Scott A. Reid, Rajendra Rathore
Spreading Electron Density Thin: Increasing The Chromophore Size In Polyaromatic Wires Decreases Interchromophoric Electronic Coupling, Mohammad Mosharraf Hossain, Maxim Vadimovich Ivanov, Denan Wang, Scott A. Reid, Rajendra Rathore
Chemistry Faculty Research and Publications
The development of novel polychromophoric materials using extended polycyclic aromatic hydrocarbons as a single large chromophore holds promise for long-range charge-transfer applications in photovoltaic devices and molecular electronics. However, it is not well-understood how the interchromophoric electronic coupling varies with the chromophore size in linearly connected molecular wires. Here, we show with the aid of electrochemistry, electronic spectroscopy, density functional theory calculations, and theoretical modeling that as the number of aromatic moieties in a single chromophore increases, the interchromophoric electronic coupling decreases and may reach negligible values if the chromophore is sufficiently large. The origin of this initially surprising result …
Molecular Actuators In Action: Electron-Transfer-Induced Conformation Transformation In Cofacially Arrayed Polyfluorenes, Denan Wang, Marat R. Talipov, Maxim Vadimovich Ivanov, Saber Mirzaei, Sergey V. Lindeman, Sheng Cai, Rajendra Rathore, Scott A. Reid
Molecular Actuators In Action: Electron-Transfer-Induced Conformation Transformation In Cofacially Arrayed Polyfluorenes, Denan Wang, Marat R. Talipov, Maxim Vadimovich Ivanov, Saber Mirzaei, Sergey V. Lindeman, Sheng Cai, Rajendra Rathore, Scott A. Reid
Chemistry Faculty Research and Publications
There is much current interest in the design of molecular actuators, which undergo reversible, controlled motion in response to an external stimulus (light, heat, oxidation, etc.). Here we describe the design and synthesis of a series of cofacially arrayed polyfluorenes (MeFnHm) with varied end-capping groups, which undergo redox-controlled electromechanical actuation. Such cofacially arrayed polyfluorenes are a model molecular scaffold to investigate fundamental processes of charge and energy transfer across a π-stacked assembly, and we show with the aid of NMR and optical spectroscopies, X-ray crystallography and DFT calculations that in the neutral state the …
Photochemical Expulsion Of Leaving Groups From A Naphthothiophene-2-Carboxamide Linked To A Chromophore, Lingzi Li
Dissertations (1934 -)
Two bichromophoric systems were synthesized which have thioxanthone as the chromophore that absorbs the incident light and a naphthothiophene-2-carboxanilide, which serves as a triplet excited state energy acceptor. Upon excitation the triplet excited state of the thioxanthone is populated via intersystem crossing, which is efficient with isc = 0.68. Based on the relative energies of the triplet excited states of thioxanthone (ET = 65 kcal mol-1) and naphthothiophene (ET = 51 kcal mol-1), the subsequent triplet excited state energy transfer to generate the triplet excited state of the naphthothiophene-2-carboxamide should be a very rapid process that is 14 kcal mol1 …
The Photodynamic And Structural Analyses Of Advanced Materials For Solar Fuel Conversion, Brian Pattengale
The Photodynamic And Structural Analyses Of Advanced Materials For Solar Fuel Conversion, Brian Pattengale
Dissertations (1934 -)
Mitigating the current and future climate and pollution issues that have been brought on by the combustion of fossil fuels is of utmost importance and will rely on, in part, the availability of renewable fuel sources. Of the possible sources of energy, solar is abundant, but must be harnessed efficiently and stored as a solar fuel to overcome the current storage issues that limit photovoltaic cells. One such fuel, H2(g), represents a carbon-neutral source of energy if it can be efficiently liberated from water via the water splitting reaction. Thus, much attention is focused on designing materials to perform the …
Design, Synthesis And Study Of Redox And Optoelectronic Properties Of Aromatic Oxidants And Polycyclic Aromatic Hydrocarbons, Mohammad Mosharraf Hossain
Design, Synthesis And Study Of Redox And Optoelectronic Properties Of Aromatic Oxidants And Polycyclic Aromatic Hydrocarbons, Mohammad Mosharraf Hossain
Dissertations (1934 -)
Organic materials play a significant role for the next generation photovoltaic devices that convert solar energy into usable forms of energy. In this regard, polycyclic aromatic hydrocarbons (PAHs) are fundamental tools in the developing area of molecular electronics and photovoltaics as they show excellent optical/electronic properties and are well-suited for applications in such developing areas as flexible display devices, field effect transistors and solar cell panels. Design and synthesis of novel materials for photovoltaics applications would require the proper understanding the mechanism of charge transport and identification of the structural features necessary in a particular molecular wire or PAH. To …
Game Of Frontier Orbitals: A View On The Rational Design Of Novel Charge-Transfer Materials, Maxim Vadimovich Ivanov, Scott A. Reid, Rajendra Rathore
Game Of Frontier Orbitals: A View On The Rational Design Of Novel Charge-Transfer Materials, Maxim Vadimovich Ivanov, Scott A. Reid, Rajendra Rathore
Chemistry Faculty Research and Publications
Since the first application of frontier molecular orbitals (FMOs) to rationalize stereospecificity of pericyclic reactions, FMOs have remained at the forefront of chemical theory. Yet, the practical application of FMOs in the rational design and synthesis of novel charge transfer materials remains under-appreciated. In this Perspective, we demonstrate that molecular orbital theory is a powerful and universal tool capable of rationalizing the observed redox/optoelectronic properties of various aromatic hydrocarbons in the context of their application as charge-transfer materials. Importantly, the inspection of FMOs can provide instantaneous insight into the interchromophoric electronic coupling and polaron delocalization in polychromophoric assemblies, and therefore …
Characterization Of Protease-Activated Receptor (Par) Ligands: Parmodulins Are Reversible Allosteric Inhibitors Of Par1-Driven Calcium Mobilization In Endothelial Cells, Disha M. Gandhi, Mark W. Majewski, Ricardo Rosas Jr., Kaitlin Kentala, Trevor J. Foster, Eric Greve, Chris Dockendorff
Characterization Of Protease-Activated Receptor (Par) Ligands: Parmodulins Are Reversible Allosteric Inhibitors Of Par1-Driven Calcium Mobilization In Endothelial Cells, Disha M. Gandhi, Mark W. Majewski, Ricardo Rosas Jr., Kaitlin Kentala, Trevor J. Foster, Eric Greve, Chris Dockendorff
Chemistry Faculty Research and Publications
Several classes of ligands for Protease-Activated Receptors (PARs) have shown impressive anti-inflammatory and cytoprotective activities, including PAR2 antagonists and the PAR1-targeting parmodulins. In order to support medicinal chemistry studies with hundreds of compounds and to perform detailed mode-of-action studies, it became important to develop a reliable PAR assay that is operational with endothelial cells, which mediate the cytoprotective effects of interest. We report a detailed protocol for an intracellular calcium mobilization assay with adherent endothelial cells in multiwell plates that was used to study a number of known and new PAR1 and PAR2 ligands, including an alkynylated version of the …
The Role Of Torsional Dynamics On Hole And Exciton Stabilization In Π‐Stacked Assemblies: Design Of Rigid Torsionomers Of A Cofacial Bifluorene, Denan Wang, Maxim Vadimovich Ivanov, Damian Kokkin, John Loman, Jin-Zhe Cai, Scott A. Reid, Rajendra Rathore
The Role Of Torsional Dynamics On Hole And Exciton Stabilization In Π‐Stacked Assemblies: Design Of Rigid Torsionomers Of A Cofacial Bifluorene, Denan Wang, Maxim Vadimovich Ivanov, Damian Kokkin, John Loman, Jin-Zhe Cai, Scott A. Reid, Rajendra Rathore
Chemistry Faculty Research and Publications
Exciton and charge delocalization across π‐stacked assemblies is of importance in biological systems and functional polymeric materials. To examine the requirements for exciton and hole stabilization, cofacial bifluorene (F2) torsionomers were designed, synthesized, and characterized: unhindered (model) MeF2, sterically hindered tBuF2, and cyclophane‐like CF2, where fluorenes are locked in a perfect sandwich orientation via two methylene linkers. This set of bichromophores with varied torsional rigidity and orbital overlap shows that exciton stabilization requires a perfect sandwich‐like arrangement, as seen by strong excimeric‐like emission only in CF2 and MeF2. …
Photoinduced Interfacial Charge Separation Dynamics In Zeolitic Imidazolate Framework, Brian Pattengale, Jier Huang
Photoinduced Interfacial Charge Separation Dynamics In Zeolitic Imidazolate Framework, Brian Pattengale, Jier Huang
Chemistry Faculty Research and Publications
Owing to their porous structure and tunable framework, zeolitic imidazolate frameworks (ZIFs) have garnered considerable attention as promising photocatalytic materials. However, little is known regarding their photophysical properties. In this work, we report the photoinduced charge separation dynamics in a ZIF-67 thin film through interfacial electron transfer (ET) to methylene blue (MB+) via ultrafast transient absorption spectroscopy. We show that the ET process occurs through two distinct pathways, including an ultrafast (<200 fs) process from the [CoII(mim)2] units located on the surface of ZIF-67 film that are directly in contact with MB+ and a relatively slower ET process …
Practical Spectrophotometric Assay For The Dape-Encoded N-Succinyl-L,L-Diaminopimelic Acid Desuccinylase, A Potential Antibiotic Target, Tahirah K. Heath, Marlon R. Lutz Jr., Cory Reidl, Estefany R. Guzman, Claire A. Herbert, Boguslaw P. Nocek, Richard C. Holz, Kenneth W. Olsen, Miguel A. Ballicora, Daniel P. Becker
Practical Spectrophotometric Assay For The Dape-Encoded N-Succinyl-L,L-Diaminopimelic Acid Desuccinylase, A Potential Antibiotic Target, Tahirah K. Heath, Marlon R. Lutz Jr., Cory Reidl, Estefany R. Guzman, Claire A. Herbert, Boguslaw P. Nocek, Richard C. Holz, Kenneth W. Olsen, Miguel A. Ballicora, Daniel P. Becker
Chemistry Faculty Research and Publications
A new enzymatic assay for the bacterial enzyme succinyl-diaminopimelate desuccinylase (DapE, E.C. 3.5.1.18) is described. This assay employs N6-methyl-N2-succinyl-L,L-diaminopimelic acid (N6-methyl-L,L-SDAP) as the substrate with ninhydrin used to detect cleavage of the amide bond of the modified substrate, wherein N6-methylation enables selective detection of the primary amine enzymatic product. Molecular modeling supported preparation of the mono-N6-methylated-L,L-SDAP as an alternate substrate for the assay, given binding in the active site of DapE predicted to be comparable to the endogenous substrate. The alternate substrate for the assay, N6 …
Synthesis Of Symmetric And Unsymmetric Secondary Amines From The Ligand-Promoted Ruthenium-Catalyzed Deaminative Coupling Reaction Of Primary Amines, Pandula T. Kirinde Arachchige, Hanbin Lee, Chae S. Yi
Synthesis Of Symmetric And Unsymmetric Secondary Amines From The Ligand-Promoted Ruthenium-Catalyzed Deaminative Coupling Reaction Of Primary Amines, Pandula T. Kirinde Arachchige, Hanbin Lee, Chae S. Yi
Chemistry Faculty Research and Publications
The catalytic system generated in situ from the tetranuclear Ru–H complex with a catechol ligand (1/L1) was found to be effective for the direct deaminative coupling of two primary amines to form secondary amines. The catalyst 1/L1 was highly chemoselective for promoting the coupling of two different primary amines to afford unsymmetric secondary amines. The analogous coupling of aniline with primary amines formed aryl-substituted secondary amines. The treatment of aniline-d7 with 4-methoxybenzylamine led to the coupling product with significant deuterium incorporation on CH2 (18% D). The most pronounced carbon isotope effect …
Synthetic Analogues Of The Snail Toxin 6-Bromo-2-Mercaptotryptamine Dimer (Brmt) Reveal That Lipid Bilayer Perturbation Does Not Underlie Its Modulation Of Voltage-Gated Potassium Channels, Chris Dockendorff, Disha M. Gandhi, Ian H. Kimball, Kenneth S. Eum, Radda Rusinova, Helgi I. Ingolfsson, Ruchi Kapoor, Thasin Peyear, Matthew W. Dodge, Stephen F. Martin, Richard W. Aldrich, Olaf S. Andersen, Jon T. Sack
Synthetic Analogues Of The Snail Toxin 6-Bromo-2-Mercaptotryptamine Dimer (Brmt) Reveal That Lipid Bilayer Perturbation Does Not Underlie Its Modulation Of Voltage-Gated Potassium Channels, Chris Dockendorff, Disha M. Gandhi, Ian H. Kimball, Kenneth S. Eum, Radda Rusinova, Helgi I. Ingolfsson, Ruchi Kapoor, Thasin Peyear, Matthew W. Dodge, Stephen F. Martin, Richard W. Aldrich, Olaf S. Andersen, Jon T. Sack
Chemistry Faculty Research and Publications
Drugs do not act solely by canonical ligand–receptor binding interactions. Amphiphilic drugs partition into membranes, thereby perturbing bulk lipid bilayer properties and possibly altering the function of membrane proteins. Distinguishing membrane perturbation from more direct protein–ligand interactions is an ongoing challenge in chemical biology. Herein, we present one strategy for doing so, using dimeric 6-bromo-2-mercaptotryptamine (BrMT) and synthetic analogues. BrMT is a chemically unstable marine snail toxin that has unique effects on voltage-gated K+ channel proteins, making it an attractive medicinal chemistry lead. BrMT is amphiphilic and perturbs lipid bilayers, raising the question of whether its action against K …
Insight Into Solvent Coordination Of An Iron Porphyrin Hydroxylamine Complex From Spectroscopy And Dft Calculations, Md. Hafizur Rahman, Michael D. Ryan
Insight Into Solvent Coordination Of An Iron Porphyrin Hydroxylamine Complex From Spectroscopy And Dft Calculations, Md. Hafizur Rahman, Michael D. Ryan
Chemistry Faculty Research and Publications
The reduction of Fe(OEP)(NO) in the presence of substituted phenols leads to a three‐electron reduction to form Fe(OEP)(NH2OH), which has been characterized by visible spectroscopy and electron stoichiometry. In this work, we have further characterized this species using infrared and 1H NMR spectroscopy, along with DFT calculations. The infrared bands in the 3400–3600 cm–1 region, due to hydroxylamine, were significantly downshifted to the 2500–2700 cm–1 region when 4‐[D1]chlorophenol replaced the normal abundance acid. Using 1H NMR spectroscopy, the hydroxylamine and the meso‐protons were identified. From DFT calculations, the 1H NMR …
Photoremovable Protecting Groups Based On Electrocyclization With Leaving Group Expulsion Via A Proposed Zwitterion, Gilbert Ndzeidze
Photoremovable Protecting Groups Based On Electrocyclization With Leaving Group Expulsion Via A Proposed Zwitterion, Gilbert Ndzeidze
Dissertations (1934 -)
The triplet excited state of thioxanthone produced by photolysis undergoes reversible triplet energy transfer with a trimethylene - linked benzothiophene-2-carboxanilide ring system. The ensuing electrocyclic ring closure of the anilide moiety produces a putative zwitterionic intermediate that is capable of expelling leaving groups (LG-) from the C-3 position of the benzothiophene ring. Stern-Volmer quenching studies with cyclohexadiene as quencher furnish the rate constants for the triplet excitation transfer in the forward and reverse directions, which can be expressed as an equilibrium constant K = 0.058. Overall, the rate of triplet excited state reaction becomes K x kr = 5.7 x …
Synthesis And Characterization Of Biomimetic Models Of Mononuclear Nonheme Iron Dioxygenases And Their Reactive Intermediates, Anne Alyse Fischer
Synthesis And Characterization Of Biomimetic Models Of Mononuclear Nonheme Iron Dioxygenases And Their Reactive Intermediates, Anne Alyse Fischer
Dissertations (1934 -)
Mononuclear non-heme iron dioxygenases (MNIDs) are a class of enzymes that catalyze a variety of reactions, from amino acid catabolism to bioremediation using molecular oxygen. This work focuses on three types of MNIDs: thiol dioxygenaes (TDOs), aminophenoldioxygenases (APDOs), and sulfoxide synthases (SOSs). TDOs, found in mammals, regulate the levels of cysteine along with other thiol-containing molecules, using molecular oxygen to convert them into their corresponding sulfinic acids. APDOs catalyze the oxidative ring cleavage in the biodegradation of nitroaromatics. SOSs are involved in the biosynthesis of large biologically relevant molecules in humans. Although this class of enzymes has gained more attention …
Nadph-Cytochrome P450 Oxidoreductase: Extraction Of The Full-Length Protein And Methyl-Trosy Nmr Of The Soluble Mutants, Sara Ali Jamal Arafeh
Nadph-Cytochrome P450 Oxidoreductase: Extraction Of The Full-Length Protein And Methyl-Trosy Nmr Of The Soluble Mutants, Sara Ali Jamal Arafeh
Master's Theses (2009 -)
NADPH-cytochrome p450 oxidoreductase (CYPOR) is a membrane-bound protein in living cells. CYPOR delivers electrons to cytochrome p450 proteins (CYPs) to catalyze metabolism of drugs and synthesis of steroids. Extraction and solubilization of CYPOR from the membrane is typically done with the TritonX-100 detergent. The amount of the solubilized protein by this detergent, however, remains relatively low to structurally analyze CYPOR with NMR spectroscopy. The goal of the first project in this thesis was to optimize the amount of the extracted CYPOR from the E. coli membrane using various detergents and additives. To this aim, non-ionic detergents with variable hydrophobicity (TritonX-100, …
From Intramolecular (Circular) In An Isolated Molecule To Intermolecular Hole Delocalization In A Two‐Dimensional Solid‐State Assembly: The Case Of Pillarene, Maxim V. Ivanov, Denan Wang, Tushar S. Navale, Sergey V. Lindeman, Rajendra Rathore
From Intramolecular (Circular) In An Isolated Molecule To Intermolecular Hole Delocalization In A Two‐Dimensional Solid‐State Assembly: The Case Of Pillarene, Maxim V. Ivanov, Denan Wang, Tushar S. Navale, Sergey V. Lindeman, Rajendra Rathore
Chemistry Faculty Research and Publications
To achieve long‐range charge transport/separation and, in turn, bolster the efficiency of modern photovoltaic devices, new molecular scaffolds are needed that can self‐assemble in two‐dimensional (2D) arrays while maintaining both intra‐ and intermolecular electronic coupling. In an isolated molecule of pillarene, a single hole delocalizes intramolecularly via hopping amongst the circularly arrayed hydroquinone ether rings. The crystallization of pillarene cation radical produces a 2D self‐assembly with three intermolecular dimeric (sandwich‐like) contacts. Surprisingly, each pillarene in the crystal lattice bears a fractional formal charge of +1.5. This unusual stoichiometry of oxidized pillarene in crystals arises from effective charge distribution within the …
Nmr Resonance Assignments Of Rnase P Protein From Thermotoga Maritima, Danyun Zeng, Benjamin P. Brown, Markus W. Voehler, Sheng Cai, Nicholas J. Reiter
Nmr Resonance Assignments Of Rnase P Protein From Thermotoga Maritima, Danyun Zeng, Benjamin P. Brown, Markus W. Voehler, Sheng Cai, Nicholas J. Reiter
Chemistry Faculty Research and Publications
Ribonuclase P (RNase P) is an essential metallo-endonuclease that catalyzes 5′ precursor-tRNA (ptRNA) processing and exists as an RNA-based enzyme in bacteria, archaea, and eukaryotes. In bacteria, a large catalytic RNA and a small protein component assemble to recognize and accurately cleave ptRNA and tRNA-like molecular scaffolds. Substrate recognition of ptRNA by bacterial RNase P requires RNA-RNA shape complementarity, intermolecular base pairing, and a dynamic protein-ptRNA binding interface. To gain insight into the binding specificity and dynamics of the bacterial protein-ptRNA interface, we report the backbone and side chain 1H, 13C, and 15N resonance assignments of the …