Open Access. Powered by Scholars. Published by Universities.®
- Discipline
- Keyword
-
- Nanocomposites (42)
- Polystyrene (25)
- Fire retardancy (22)
- Cone calorimetry (13)
- Spectroelectrochemistry (11)
-
- Poly(methyl methacrylate) (10)
- Thermal stability (10)
- Inelastic scattering (8)
- NMR (8)
- Nanocomposite (8)
- Thermal degradation (8)
- Cobalt (7)
- Fire Retardancy (7)
- Iron (7)
- X-ray structures (7)
- Cross-linking (6)
- Crystal structure (6)
- Cyclic voltammetry (6)
- Electrochemistry (6)
- Ionic liquid (6)
- Layered double hydroxide (6)
- Molecular data (6)
- Oxidation (6)
- Cytochrome P450 (5)
- Kinetics (5)
- Layered double hydroxides (5)
- Polyethylene (5)
- Wave functions (5)
- XPS (5)
- Zinc (5)
- Publication Year
Articles 91 - 120 of 690
Full-Text Articles in Chemistry
Proton Transfer Versus Hydrogen Bonding In A Reduced Iron Porphyrin Nitrosyl Complex, Md. Hafizur Rahman, Yilin Liu, Michael D. Ryan
Proton Transfer Versus Hydrogen Bonding In A Reduced Iron Porphyrin Nitrosyl Complex, Md. Hafizur Rahman, Yilin Liu, Michael D. Ryan
Chemistry Faculty Research and Publications
The 1H NMR spectra of Fe(OEP)(HNO), which was formed from Fe(OEP)(NO)− in the presence of 3,5-dichlorophenol, were studied as a function of temperature. The chemical shift of the HNO proton showed a unique behavior which could be explained based on the equilibrium between the protonated complex, Fe(OEP)(HNO), and the hydrogen-bonded complex, Fe(OEP)(NO)−···HOPh. This equilibrium was consistent with UV/visible spectroscopy and the voltammetric data. UV/visible stopped-flow experiments showed that the hydrogen-bonded complex, which was formed when weak acids such as phenol were added, and the Fe(OEP)(HNO) complex were quite similar. In addition to the HNO proton resonance, …
Empirical Mappings Of The Frequency Response Of An Electron Ratchet To The Characteristics Of The Polymer Transport Layer, Mohamad S. Kodaimati, Ofer Kedem, George C. Schatz, Emily A. Weiss
Empirical Mappings Of The Frequency Response Of An Electron Ratchet To The Characteristics Of The Polymer Transport Layer, Mohamad S. Kodaimati, Ofer Kedem, George C. Schatz, Emily A. Weiss
Chemistry Faculty Research and Publications
Flashing electron ratchets oscillate a periodic asymmetric potential to rectify nondirectional forces and thereby produce directional transport of electrons with zero source-drain bias. The relationship between the oscillation frequency of the potential and the ratchet (short-circuit) current reflects microscopic mechanisms of charge transport within the device. This paper describes experimental mappings of the “optimal frequency(ies)” of the ratchet fpeak—the oscillation frequencies that produce the largest ratchet current—to the carrier concentration, nh, and to the linear field effect transistor mobility, μh, for a poly(3-hexylthiophene-2,5-diyl) (P3HT) transport layer. Measurements on multiple devices, multiple P3HT films per …
Evaluation Of Α-Hydroxycinnamic Acids As Pyruvate Carboxylase Inhibitors, Daniel J. Burkett, Brittney N. Wyatt, Mallory Mews, Anson Bautista, Ryan Engel, Chris Dockendorff, William A. Donaldson, Martin St. Maurice
Evaluation Of Α-Hydroxycinnamic Acids As Pyruvate Carboxylase Inhibitors, Daniel J. Burkett, Brittney N. Wyatt, Mallory Mews, Anson Bautista, Ryan Engel, Chris Dockendorff, William A. Donaldson, Martin St. Maurice
Chemistry Faculty Research and Publications
Through a structure-based drug design project (SBDD), potent small molecule inhibitors of pyruvate carboxylase (PC) have been discovered. A series of α-keto acids (7) and α-hydroxycinnamic acids (8) were prepared and evaluated for inhibition of PC in two assays. The two most potent inhibitors were 3,3′-(1,4-phenylene)bis[2-hydroxy-2-propenoic acid] (8u) and 2-hydroxy-3-(quinoline-2-yl)propenoic acid (8v) with IC50 values of 3.0 ± 1.0 μM and 4.3 ± 1.5 μM respectively. Compound 8v is a competitive inhibitor with respect to pyruvate (Ki = 0.74 μM) and a mixed-type inhibitor with respect to ATP, indicating …
The Parmodulin Nrd-21 Is An Allosteric Inhibitor Of Par1 Gq Signaling With Improved Anti-Inflammatory Activity And Stability, Disha M. Gandhi, Ricardo Rosas Jr., Eric Greve, Kaitlin Kentala, N'Guessan D.-R, Diby, Vladyslava A. Snyder, Allison Stephans, Teresa H.W. Yeung, Saravanan Subramaniam, Elliot Dimilo, Khia E. Kurtenbach, Leggy A. Arnold, Hartmut Weiler, Chris Dockendorff
The Parmodulin Nrd-21 Is An Allosteric Inhibitor Of Par1 Gq Signaling With Improved Anti-Inflammatory Activity And Stability, Disha M. Gandhi, Ricardo Rosas Jr., Eric Greve, Kaitlin Kentala, N'Guessan D.-R, Diby, Vladyslava A. Snyder, Allison Stephans, Teresa H.W. Yeung, Saravanan Subramaniam, Elliot Dimilo, Khia E. Kurtenbach, Leggy A. Arnold, Hartmut Weiler, Chris Dockendorff
Chemistry Faculty Research and Publications
Novel analogs of the allosteric, biased PAR1 ligand ML161 (parmodulin 2, PM2) were prepared in order to identify potential anti-thrombotic and anti-inflammatory compounds of the parmodulin class with improved properties. Investigations of structure-activity relationships of the western portion of the 1,3-diaminobenzene scaffold were performed using an intracellular calcium mobilization assay with endothelial cells, and several heterocycles were identified that inhibited PAR1 at sub-micromolar concentrations. The oxazole NRD-21 was profiled in additional detail, and it was confirmed to act as a selective, reversible, negative allosteric modulator of PAR1. In addition to inhibiting human platelet aggregation, it showed superior anti-inflammatory activity to …
Β-Fluorofentanyls Are Ph-Sensitive Mu Opioid Receptor Agonists, Ricardo Rosas Jr., Xi-Ping Huang, Bryan L. Roth, Chris Dockendorff
Β-Fluorofentanyls Are Ph-Sensitive Mu Opioid Receptor Agonists, Ricardo Rosas Jr., Xi-Ping Huang, Bryan L. Roth, Chris Dockendorff
Chemistry Faculty Research and Publications
The concept recently postulated by Stein and co-workers (Science2017, 355, 966) that mu opioid receptor (MOR) agonists possessing amines with attenuated basicity show pH-dependent activity and can selectively act at damaged, low pH tissues has been additionally supported by in vitro studies reported here. We synthesized and tested analogs of fentanyl possessing one or two fluorine atoms at the beta position of the phenethylamine side chain, with additional fluorines optionally added to the benzene ring of the side chain. These compounds were synthesized in 1 to 3 steps from commercial building blocks. The novel bis-fluorinated analog …
Improving Performance Of The Smd Solvation Model: Bondi Radii Improve Predicted Aqueous Solvation Free Energies Of Ions And PkA Values Of Thiols, Saber Mirzaei, Maxim Vadimovich Ivanov, Qadir K. Timerghazin
Improving Performance Of The Smd Solvation Model: Bondi Radii Improve Predicted Aqueous Solvation Free Energies Of Ions And PkA Values Of Thiols, Saber Mirzaei, Maxim Vadimovich Ivanov, Qadir K. Timerghazin
Chemistry Faculty Research and Publications
Calculation of the solvation free energy of ionic molecules is the principal source of errors in the quantum chemical evaluation of pKa values using implicit polarizable continuum solvent models. One of the important parameters affecting the performance of these models is the choice of atomic radii. Here, we assess the performance of the solvation model based on density (SMD) implicit solvation model employing SMD default radii (SMD) and Bondi radii (SMD-B), a set of empirical atomic radii developed based on the crystallographic data. For a set of 112 ions (60 anions and 52 cations), the SMD-B model showed …
Calculation Of Molecular Vibrational Spectra On A Quantum Annealer, Alexander Teplukhin, Brian K. Kendrick, Dmitri Babikov
Calculation Of Molecular Vibrational Spectra On A Quantum Annealer, Alexander Teplukhin, Brian K. Kendrick, Dmitri Babikov
Chemistry Faculty Research and Publications
Until recently molecular energy calculations using quantum computing hardware have been limited to gate-based quantum computers. In this paper, a new methodology is presented to calculate the vibrational spectrum of a molecule on a quantum annealer. The key idea of the method is a mapping of the ground state variational problem onto an Ising or quadratic unconstrained binary optimization (QUBO) problem by expressing the expansion coefficients using spins or qubits. The algorithm is general and represents a new revolutionary approach for solving the real symmetric eigenvalue problem on a quantum annealer. The method is applied to two chemically important molecules: …
Selective Excited-State Dynamics In A Unique Set Of Rationally Designed Ni Porphyrins, Brian Pattengale, Qiuhua Liu, Wenhui Hu, Sizhuo Yang, Peilei He, Sir Lawrence Tender, Yingqi Wang, Xiaoyi Zhang, Zaichun Zhou, Jian Zhang, Jier Huang
Selective Excited-State Dynamics In A Unique Set Of Rationally Designed Ni Porphyrins, Brian Pattengale, Qiuhua Liu, Wenhui Hu, Sizhuo Yang, Peilei He, Sir Lawrence Tender, Yingqi Wang, Xiaoyi Zhang, Zaichun Zhou, Jian Zhang, Jier Huang
Chemistry Faculty Research and Publications
In this work, we report the design and photophysical properties of a unique class of Ni porphyrins, in which the tert-butyl benzene substituents at the meso positions of the macrocycle were tethered by ethers with alkyl linkers. This not only results in the permanently locked ruf distortion of the macrocycle but also enables the engineering of the degree of distortion through varying the length of alkyl linkers, which addressed the complication of uncertainty in the specific structural distortions that has long plagued the porphyrin photophysical community. Using advanced time-resolved optical and X-ray absorption spectroscopy, we observed tunability in the …
Selective Isomer Formation And Crystallization-Directed Magnetic Behavior In Nitrogen-Confused C-Scorpionate Complexes Of Fe(O3Scf3)2, James R. Gardinier, Kristin J. Meise, Fathiya Jahan, Denan Wang, Sergey V. Lindeman
Selective Isomer Formation And Crystallization-Directed Magnetic Behavior In Nitrogen-Confused C-Scorpionate Complexes Of Fe(O3Scf3)2, James R. Gardinier, Kristin J. Meise, Fathiya Jahan, Denan Wang, Sergey V. Lindeman
Chemistry Faculty Research and Publications
The complex [Fe(HL*)2](OTf)2, 1, where HL* = bis(3,5-dimethylpyrazol-1-yl)(3-1H-pyrazole)methane, was prepared in order to compare its magnetic properties with those of the analogous parent complex, [Fe(HL)2](OTf)2, that lacks methyl groups on pyrazolyl rings and that undergoes spin crossover (SCO) from the low spin (LS) to the high spin (HS) form above room temperature. It was anticipated that this new semibulky derivative should favor the HS state and undergo SCO at a lower temperature range. During this study, six crystalline forms of 1 were prepared by …
Charge-Transfer Or Excimeric State? Exploring The Nature Of The Excited State In Cofacially Arrayed Polyfluorene Derivatives, Ainur Abzhanova, Lena V. Ivanova, Denan Wang, Tushar S. Navale, Sameh H. Abdelwahed, Maxim Vadimovich Ivanov, Sergey V. Lindeman, Rajendra Rathore, Scott A. Reid
Charge-Transfer Or Excimeric State? Exploring The Nature Of The Excited State In Cofacially Arrayed Polyfluorene Derivatives, Ainur Abzhanova, Lena V. Ivanova, Denan Wang, Tushar S. Navale, Sameh H. Abdelwahed, Maxim Vadimovich Ivanov, Sergey V. Lindeman, Rajendra Rathore, Scott A. Reid
Chemistry Faculty Research and Publications
It is well known that upon electronic excitation various π-stacked dimers readily exhibit excimer formation, facilitated by a perfect sandwich-like arrangement between the chromophores. However, it is unclear whether such a dimer is also capable of electron transfer upon excitation, if a strong electron-donating group is covalently attached. In this work, we probe the nature of the excited state in a series of cofacially arrayed polyfluorene derivatives with electron-rich aromatic donor attached via a methylene linker. Our studies show that in all cases excimer formation is energetically favorable, and promotion of a charge-transfer state in such systems is possible but …
Synthesis Of Simplified Azasordarin Analogs As Potential Antifungal Agents, Yibiao Wu, Chris Dockendorff
Synthesis Of Simplified Azasordarin Analogs As Potential Antifungal Agents, Yibiao Wu, Chris Dockendorff
Chemistry Faculty Research and Publications
A new series of simplified azasordarin analogs was synthesized using as key steps a Diels–Alder reaction to generate a highly substituted bicyclo[2.2.1]heptane core, followed by a subsequent nitrile alkylation. Several additional strategies were investigated for the generation of the key tertiary nitrile or aldehyde thought to be required for inhibition at the fungal protein eukaryotic elongation factor 2. This new series also features a morpholino glycone previously reported in semisynthetic sordarin derivatives with broad spectrum antifungal activity. Despite a lack of activity against Candida albicans for these early de novo analogs, the synthetic route reported here permits more comprehensive modifications …
Cooperative Transport In A Multi-Particle, Multi-Dimensional Flashing Ratchet, Ofer Kedem, Emily A. Weiss
Cooperative Transport In A Multi-Particle, Multi-Dimensional Flashing Ratchet, Ofer Kedem, Emily A. Weiss
Chemistry Faculty Research and Publications
Random and undirected forces are rectified in biological and synthetic systems using ratcheting mechanisms, which employ periodic asymmetric potentials and nonequilibrium conditions to produce useful transport. The density of motors or transported particles is known to strongly affect the nature and efficacy of transport in biological systems, as well as in synthetic ratchets and active swimmer systems. While experimental ratchet implementations typically employ potentials varying in two dimensions (2D), the role of the density of interacting particles in such a system has not been modeled. Prompted by experimental observations and building upon previous simulations, this paper describes the ratcheting process …
The Ratio Of The Number Of States In Asymmetric And Symmetric Ozone Molecules Deviates From The Statistical Value Of 2, Igor Gayday, Alexander Teplukhin, Dmitri Babikov
The Ratio Of The Number Of States In Asymmetric And Symmetric Ozone Molecules Deviates From The Statistical Value Of 2, Igor Gayday, Alexander Teplukhin, Dmitri Babikov
Chemistry Faculty Research and Publications
Accurate calculations of vibrational states in singly and doubly substituted ozone molecules are carried out, up to dissociation threshold. Analysis of these spectra reveals noticeable deviations from the statistical factor of 2 for the ratio between the number of states in asymmetric and symmetric ozone molecules. It is found that, for the lower energy parts of spectra, the ratio is less than 2 in the singly substituted ozone molecules, but it is more than 2 in the doubly substituted ozone molecules. However, the upper parts of spectra, just below dissociation thresholds, exhibit a different behavior. In this energy range, the …
C–H/Π And C–H–O Interactions In Concert: A Study Of The Anisole–Methane Complex Using Resonant Ionization And Velocity Mapped Ion Imaging, James Makuvaza, Damian Kokkin, John Loman, Scott A. Reid
C–H/Π And C–H–O Interactions In Concert: A Study Of The Anisole–Methane Complex Using Resonant Ionization And Velocity Mapped Ion Imaging, James Makuvaza, Damian Kokkin, John Loman, Scott A. Reid
Chemistry Faculty Research and Publications
Noncovalent forces such as hydrogen bonding, halogen bonding, π–π stacking, and C–H/π and C–H/O interactions hold the key to such chemical processes as protein folding, molecular self-assembly, and drug–substrate interactions. Invaluable insight into the nature and strength of these forces continues to come from the study of isolated molecular clusters. In this work, we report on a study of the isolated anisole–methane complex, where both C–H/π and C–H/O interactions are possible, using a combination of theory and experiments that include mass-selected two-color resonant two-photon ionization spectroscopy, two-color appearance potential (2CAP) measurements, and velocity mapped ion imaging (VMI). Using 2CAP and …
Proton-Coupled Reduction Of An Iron Nitrosyl Porphyrin In The Protic Ionic Liquid Nanodomain, Abderrahman Atifi, Piotr J. Mak, Michael D. Ryan
Proton-Coupled Reduction Of An Iron Nitrosyl Porphyrin In The Protic Ionic Liquid Nanodomain, Abderrahman Atifi, Piotr J. Mak, Michael D. Ryan
Chemistry Faculty Research and Publications
The one-electron reduction of many molecules becomes much more favorable if combined with proton transfers or strong hydrogen bonding. Protic room temperature ionic liquids (RTILs), which can form nanodomains in solutions with molecular solvents (MS), can provide an efficient avenue for this process. In this work, we report on the voltammetry, UV/visible and resonance Raman spectroelectrochemistryof Fe(TPP)(NO) in the presence of aprotic/protic ammonium-based ionic liquids. While aprotic RTILs did shift the reduction to more positive potentials, similar shifts could be observed at much lower concentrations of diethylmethylammonium triflate (HAmOTf, a protic ionic liquid). Deconvolution of the rotating ring-disk electrode (RRDE) …
Design And Evaluation Of Heterobivalent Par1–Par2 Ligands As Antagonists Of Calcium Mobilization, Mark W. Majewski, Disha M. Gandhi, Ricardo Rosas Jr., Revathi Kodall, Leggy A. Arnold, Chris Dockendorff
Design And Evaluation Of Heterobivalent Par1–Par2 Ligands As Antagonists Of Calcium Mobilization, Mark W. Majewski, Disha M. Gandhi, Ricardo Rosas Jr., Revathi Kodall, Leggy A. Arnold, Chris Dockendorff
Chemistry Faculty Research and Publications
A novel class of bivalent ligands targeting putative protease-activated receptor (PAR) heteromers has been prepared based upon reported antagonists for the subtypes PAR1 and PAR2. Modified versions of the PAR1 antagonist RWJ-58259 containing alkyne adapters were connected via cycloaddition reactions to azide-capped polyethylene glycol (PEG) spacers attached to imidazopyridazine-based PAR2 antagonists. Initial studies of the PAR1–PAR2 antagonists indicated that they inhibited G alpha q-mediated calcium mobilization in endothelial and cancer cells driven by both PAR1 and PAR2 agonists. Compounds of this novel class hold promise for the prevention of restenosis, cancer cell metastasis, and other proliferative disorders.
Investigation Of Solvation And Solvent Coordination Effects In Iron Porphyrin Nitrosyls By Infrared Spectroelectrochemistry And Dft Calculations, Md. Hafizur Rahman, Michael D. Ryan
Investigation Of Solvation And Solvent Coordination Effects In Iron Porphyrin Nitrosyls By Infrared Spectroelectrochemistry And Dft Calculations, Md. Hafizur Rahman, Michael D. Ryan
Chemistry Faculty Research and Publications
Visible and infrared spectroelectrochemistry of Fe(OEPone)(NO) (H2OEPone = octaethylporphinone) were examined in methylene chloride and THF. The visible spectra of Fe(OEPone)(NO) were similar in both solvents. Unlike other ferrous porphyrin nitrosyls, a six-coordinate complex was formed with THF as a ligand. This led to two nitrosyl bands in the infrared spectrum. The absorbance of these bands depended on the concentration of THF in the solution. Solvation and coordination effects on the carbonyl and nitrosyl bands were observed for both the nitrosyl and reduced-nitrosyl complexes. DFT calculations were carried out to interpret the spectral changes.
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 …