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Articles 1 - 30 of 32
Full-Text Articles in Physical Sciences and Mathematics
The Effect Of Mo Doping On The Charge Separation Dynamics And Photocurrent Performance Of Bivo4 Photoanodes, Brian Pattengale, Jier Huang
The Effect Of Mo Doping On The Charge Separation Dynamics And Photocurrent Performance Of Bivo4 Photoanodes, Brian Pattengale, Jier Huang
Chemistry Faculty Research and Publications
Doping with electron-rich elements in BiVO4 photoanodes has been demonstrated as a desirable approach for improving their carrier mobility and charge separation efficiency. However, the effect of doping and dopant concentration on the carrier dynamics and photoelectrochemical performance remains unclear. In this work, we examined the effects of Mo doping on the charge separation dynamics and photocurrent performance in BiVO4photoanodes. We show that the photocurrent of BiVO4 photoanodes increases with increasing concentration of the Mo dopant, which can be attributed to both the improved carrier mobility resulting from increased electron density and charge separation efficiency due …
Dihedral-Angle-Controlled Crossover From Static Hole Delocalization To Dynamic Hopping In Biaryl Cation Radicals, Marat R. Talipov, Tushar S. Navale, Mohammad M. Hossain, Ruchi Shukla, Maxim V. Ivanov, Rajendra Rathore
Dihedral-Angle-Controlled Crossover From Static Hole Delocalization To Dynamic Hopping In Biaryl Cation Radicals, Marat R. Talipov, Tushar S. Navale, Mohammad M. Hossain, Ruchi Shukla, Maxim V. Ivanov, Rajendra Rathore
Chemistry Faculty Research and Publications
In cases of coherent charge-transfer mechanism in biaryl compounds the rates follow a squared cosine trend with varying dihedral angle. Herein we demonstrate using a series of biaryl cation radicals with varying dihedral angles that the hole stabilization shows two different regimes where the mechanism of the hole stabilization switches over from (static) delocalization over both aryl rings to (dynamic) hopping. The experimental data and DFT calculations of biaryls with different dihedral angles unequivocally support that a crossover from delocalization to hopping occurs at a unique dihedral angle where the electronic coupling (Hab) is one half of …
Synthesis, X-Ray Structures, Electronic Properties, And O2/No Reactivities Of Thiol Dioxygenase Active-Site Models, Anne A. Fischer, Nuru Stracey, Sergey V. Lindeman, Thomas C. Brunold, Adam T. Fiedler
Synthesis, X-Ray Structures, Electronic Properties, And O2/No Reactivities Of Thiol Dioxygenase Active-Site Models, Anne A. Fischer, Nuru Stracey, Sergey V. Lindeman, Thomas C. Brunold, Adam T. Fiedler
Chemistry Faculty Research and Publications
Mononuclear non-heme iron complexes that serve as structural and functional mimics of the thiol dioxygenases (TDOs), cysteine dioxygenase (CDO) and cysteamine dioxygenase (ADO), have been prepared and characterized with crystallographic, spectroscopic, kinetic, and computational methods. The high-spin Fe(II) complexes feature the facially coordinating tris(4,5-diphenyl-1-methylimidazol-2-yl)phosphine (Ph2TIP) ligand that replicates the three histidine (3His) triad of the TDO active sites. Further coordination with bidentate l-cysteine ethyl ester (CysOEt) or cysteamine (CysAm) anions yielded five-coordinate (5C) complexes that resemble the substrate-bound forms of CDO and ADO, respectively. Detailed electronic-structure descriptions of the [Fe(Ph2TIP)(LS,N)]BPh4 complexes, where L …
Critical Role Of The Secondary Binding Pocket In Modulating The Enzymatic Activity Of Dusp5 Toward Phosphorylated Erks, Marat R. Talipov, Jaladhi Nayak, Michael Lepley, Robert D. Bongard, Daniel Sem, Ramani Ramchandran, Rajendra Rathore
Critical Role Of The Secondary Binding Pocket In Modulating The Enzymatic Activity Of Dusp5 Toward Phosphorylated Erks, Marat R. Talipov, Jaladhi Nayak, Michael Lepley, Robert D. Bongard, Daniel Sem, Ramani Ramchandran, Rajendra Rathore
Chemistry Faculty Research and Publications
DUSP5 is an inducible nuclear dual-specificity phosphatase that specifically interacts with and deactivates extracellular signal-regulated kinases ERK1 and ERK2, which are responsible for cell proliferation, differentiation, and survival. The phosphatase domain (PD) of DUSP5 has unique structural features absent from other nuclear DUSPs, such as the presence of a secondary anion-binding site in the proximity of the reaction center and a glutamic acid E264 positioned next to the catalytic cysteine C263, as well as a remote intramolecular disulfide linkage. The overall 400 ns molecular dynamics simulations indicate that the secondary binding site of DUSP5 PD acts as an allosteric regulator …
Conformational States Of Cytochrome P450 Oxidoreductase Evaluated By Förster Resonance Energy Transfer Using Ultrafast Transient Absorption Spectroscopy, Elizaveta A. Kovrigina, Brian Pattengale, Chuanwu Xia, Azamat R. Galiakhmetov, Jier Huang, Jung Ja Kim, Evgueni Kovrigin
Conformational States Of Cytochrome P450 Oxidoreductase Evaluated By Förster Resonance Energy Transfer Using Ultrafast Transient Absorption Spectroscopy, Elizaveta A. Kovrigina, Brian Pattengale, Chuanwu Xia, Azamat R. Galiakhmetov, Jier Huang, Jung Ja Kim, Evgueni Kovrigin
Chemistry Faculty Research and Publications
NADPH-cytochrome P450 oxidoreductase (CYPOR) was shown to undergo large conformational rearrangements in its functional cycle. Using a new Förster resonance energy transfer (FRET) approach based on femtosecond transient absorption spectroscopy (TA), we determined the donor–acceptor distance distribution in the reduced and oxidized states of CYPOR. The unmatched time resolution of TA allowed the quantitative assessment of the donor–acceptor FRET, indicating that CYPOR assumes a closed conformation in both reduced and oxidized states in the absence of the redox partner. The described ultrafast TA measurements of FRET with readily available red–infrared fluorescent labels open new opportunities for structural studies in chromophore-rich …
Synthesis, Structure And Antimicrobial Property Of Green Composites From Cellulose, Wool, Hair And Chicken Feather, Chieu D. Tran, Franja Prosenc, Mladen Franko, Gerald Benzi
Synthesis, Structure And Antimicrobial Property Of Green Composites From Cellulose, Wool, Hair And Chicken Feather, Chieu D. Tran, Franja Prosenc, Mladen Franko, Gerald Benzi
Chemistry Faculty Research and Publications
Novel composites between cellulose (CEL) and keratin (KER) from three different sources (wool, hair and chicken feather) were successfully synthesized in a simple one-step process in which butylmethylimidazolium chloride (BMIm+Cl−), an ionic liquid, was used as the sole solvent. The method is green and recyclable because [BMIm+Cl−] used was recovered for reuse. Spectroscopy (FTIR, XRD) and imaging (SEM) results confirm that CEL and KER remain chemically intact and homogeneously distributed in the composites. KER retains some of its secondary structure in the composites. Interestingly, the minor differences in the structure of KER …
Evidence That Cytochrome B5 Acts As A Redox Donor In Cyp17a1 Mediated Androgen Synthesis, Ruchia Duggal, Yilin Liu, Michael C. Gregory, Ilia G. Denisov, James R. Kincaid, Stephen G. Sligar
Evidence That Cytochrome B5 Acts As A Redox Donor In Cyp17a1 Mediated Androgen Synthesis, Ruchia Duggal, Yilin Liu, Michael C. Gregory, Ilia G. Denisov, James R. Kincaid, Stephen G. Sligar
Chemistry Faculty Research and Publications
Cytochrome P450 17A1 (CYP17A1) is an important drug target for castration resistant prostate cancer. It is a bi-functional enzyme, catalyzing production of glucocorticoid precursors by hydroxylation of pregnene-nucleus, and androgen biosynthesis by a second C--C lyase step, at the expense of glucocorticoid production. Cytochrome b5(cyt b5) is known to be a key regulator of the androgen synthesis reaction in vivo, by a mechanism that is not well understood. Two hypotheses have been proposed for the mechanism by which cyt b5 increases androgen biosynthesis. Cyt b5 could act as an allosteric effector, binding to …
First Experimental Evidence For The Diverse Requirements Of Excimer Vs Hole Stabilization In Π-Stacked Assemblies, Neil Reilly, Maxim Vadimovich Ivanov, Brandon Uhler, Marat R. Talipov, Rajendra Rathore, Scott Reid
First Experimental Evidence For The Diverse Requirements Of Excimer Vs Hole Stabilization In Π-Stacked Assemblies, Neil Reilly, Maxim Vadimovich Ivanov, Brandon Uhler, Marat R. Talipov, Rajendra Rathore, Scott Reid
Chemistry Faculty Research and Publications
Exciton formation and charge separation and transport are key dynamical events in a variety of functional polymeric materials and biological systems, including DNA. Beyond the necessary cofacial approach of a pair of aromatic molecules at van der Waals contact, the extent of overlap and necessary geometrical reorganization for optimal stabilization of an excimer vs dimer cation radical remain unresolved. Here, we compare experimentally the dynamics of excimer formation (via emission) and charge stabilization (via threshold ionization) of a novel covalently linked, cofacially stacked fluorene dimer (F2) with the unlinked van der Waals dimer of fluorene, that is, (F)2. …
Two's Company, Three's A Crowd: Exciton Localization In Cofacially Arrayed Polyfluorenes, Marat R. Talipov, Maxim Vadimovich Ivanov, Scott Reid, Rajendra Rathore
Two's Company, Three's A Crowd: Exciton Localization In Cofacially Arrayed Polyfluorenes, Marat R. Talipov, Maxim Vadimovich Ivanov, Scott Reid, Rajendra Rathore
Chemistry Faculty Research and Publications
Understanding the mechanisms of long-range energy transfer through polychromophoric assemblies is critically important in photovoltaics and biochemical systems. Using a set of cofacially arrayed polyfluorenes (Fn), we investigate the mechanism of (singlet) exciton delocalization in π-stacked polychromophoric assemblies. Calculations reveal that effective stabilization of an excimeric state requires an ideal sandwich-like arrangement; yet surprisingly, emission spectroscopy indicates that exciton delocalization is limited to only two fluorene units for all n. Herein, we show that delocalization is determined by the interplay between the energetic gain from delocalization, which quickly saturates beyond two units in larger Fn, …
Analysis Of Heme Iron Coordination In Dgcr8: The Heme-Binding Component Of The Microprocessor Complex, Hazel M. Girvan, Justin M. Bradley, Myles R. Cheesman, James R. Kincaid, Yilin Liu, Kazimierz Czarnecki, Karl Fisher, David Leys, Stephen E. J. Rigby, Andrew W. Munro
Analysis Of Heme Iron Coordination In Dgcr8: The Heme-Binding Component Of The Microprocessor Complex, Hazel M. Girvan, Justin M. Bradley, Myles R. Cheesman, James R. Kincaid, Yilin Liu, Kazimierz Czarnecki, Karl Fisher, David Leys, Stephen E. J. Rigby, Andrew W. Munro
Chemistry Faculty Research and Publications
DGCR8 is the RNA-binding partner of the nuclease Drosha. Their complex (the “Microprocessor”) is essential for processing of long, primary microRNAs (pri-miRNAs) in the nucleus. Binding of heme to DGCR8 is essential for pri-miRNA processing. On the basis of the split Soret ultraviolet–visible (UV–vis) spectrum of ferric DGCR8, bis-thiolate sulfur (cysteinate, Cys–) heme iron coordination of DGCR8 heme iron was proposed. We have characterized DGCR8 heme ligation using the Δ276 DGCR8 variant and combined electron paramagnetic resonance (EPR), magnetic circular dichroism (MCD), electron nuclear double resonance, resonance Raman, and electronic absorption spectroscopy. These studies indicate DGCR8 bis-Cys heme …
Efficient Method For Calculations Of Ro-Vibrational States In Triatomic Molecules Near Dissociation Threshold: Application To Ozone, Alexander Teplukhin, Dmitri Babikov
Efficient Method For Calculations Of Ro-Vibrational States In Triatomic Molecules Near Dissociation Threshold: Application To Ozone, Alexander Teplukhin, Dmitri Babikov
Chemistry Faculty Research and Publications
A method for calculations of rotational-vibrational states of triatomic molecules up to dissociation threshold (and scattering resonances above it) is devised, that combines hyper-spherical coordinates, sequential diagonalization-truncation procedure, optimized grid DVR, and complex absorbing potential. Efficiency and accuracy of the method and new code are tested by computing the spectrum of ozone up to dissociation threshold, using two different potential energy surfaces. In both cases good agreement with results of previous studies is obtained for the lower energy states localized in the deep (∼10 000 cm−1) covalent well. Upper part of the bound state spectrum, within 600 cm−1 below dissociation …
Multifunctional Heterocyclic Scaffolds For Hybrid Lewis Acid/Lewis Base Catalysis Of Carbon–Carbon Bond Formation, Dennis Wiedenhoeft, Adam R. Benoit, Yibiao Wu, Jacob D. Porter, Elisia Meyle, Teresa H.W. Yeung, Raechel Huff, Sergey Lindeman, Chris Dockendorff
Multifunctional Heterocyclic Scaffolds For Hybrid Lewis Acid/Lewis Base Catalysis Of Carbon–Carbon Bond Formation, Dennis Wiedenhoeft, Adam R. Benoit, Yibiao Wu, Jacob D. Porter, Elisia Meyle, Teresa H.W. Yeung, Raechel Huff, Sergey Lindeman, Chris Dockendorff
Chemistry Faculty Research and Publications
No abstract provided.
Supramolecular Assembly Of Metal-Organic Tubes Constructed From The Ditopic Heteroscorpionate Ligand (4-Nh2C6H4)Chpz2 (Pz = Pyrazol-1-Yl) And Silver(I), James R. Gardinier, Jeewantha S. Hewage, Justin Hoffman, Sergey V. Lindeman, Natalia B. Shustova
Supramolecular Assembly Of Metal-Organic Tubes Constructed From The Ditopic Heteroscorpionate Ligand (4-Nh2C6H4)Chpz2 (Pz = Pyrazol-1-Yl) And Silver(I), James R. Gardinier, Jeewantha S. Hewage, Justin Hoffman, Sergey V. Lindeman, Natalia B. Shustova
Chemistry Faculty Research and Publications
The possibility of constructing tubular metal-organic structures with aid of weak hydrogen-bonding interactions between suitably designed metallacycles was explored. For this purpose, the new heteroditopic ligand (4-NH2C6H4)CHpz2 (L1) was prepared in good (75 %) yield by a one-pot procedure starting from commercial 4-acetamidobenzaldehyde. The equimolar reactions between L1 and various silver(I) salts gave the intended 1:1 complexes in which the metallacycles were assembled into tubes. However, the exact nature of the assemblies (including their solvate compositions) varied depending on anion, solvent, and concentration of the original crystallization solution. For the trifluoromethanesulfonate anion, a …
Mononuclear Iron-(Hydro/Semi)Quinonate Complexes Featuring Neutral And Charged Scorpionates: Synthetic Models Of Intermediates In The Hydroquinone Dioxygenase Mechanism, Amanda E. Baum, Sergey V. Lindeman, Adam T. Fiedler
Mononuclear Iron-(Hydro/Semi)Quinonate Complexes Featuring Neutral And Charged Scorpionates: Synthetic Models Of Intermediates In The Hydroquinone Dioxygenase Mechanism, Amanda E. Baum, Sergey V. Lindeman, Adam T. Fiedler
Chemistry Faculty Research and Publications
Neutral and anionic scorpionate ligands have been employed to generate active-site models of hydroquinone dioxygenases (HQDOs). While the nonheme Fe center in nearly all HQDOs is coordinated to one Asp (or Glu) and two His residues, 1,2-gentisate dioxygenase (GDO) is unique in featuring a three His triad instead. A synthetic GDO model was therefore prepared with the neutral tris(4,5-diphenyl-1-methylimidazol-2-yl)phosphine (Ph2TIP) ligand. The gentisate substrate was mimicked with the bidentate ligand 2-(1-methylbenzimidazol-2-yl)hydroquinonate (BIHQ). X-ray diffraction analysis of the resulting complex, [Fe(Ph2TIP)(BIHQ)]OTf (1a), revealed a distorted square-pyramidal geometry. Structural and electrochemical data collected for 1a were compared to …
The Use Of Isomeric Testosterone Dimers To Explore Allosteric Effects In Substrate Binding To Cytochrome P450 Cyp3a4, Ilia G. Denisov, Piotr J. Mak, Yelena V. Grinkova, Dominic Bastien, Gervais Bérubé, Stephen G. Sligar, James R. Kincaid
The Use Of Isomeric Testosterone Dimers To Explore Allosteric Effects In Substrate Binding To Cytochrome P450 Cyp3a4, Ilia G. Denisov, Piotr J. Mak, Yelena V. Grinkova, Dominic Bastien, Gervais Bérubé, Stephen G. Sligar, James R. Kincaid
Chemistry Faculty Research and Publications
Abstract: Cytochrome P450 CYP3A4 is the main drug-metabolizing enzyme in the human liver, being responsible for oxidation of 50% of all pharmaceuticals metabolized by human P450 enzymes. Possessing a large substrate binding pocket, it can simultaneously bind several substrate molecules and often exhibits a complex pattern of drug–drug interactions. In order to better understand structural and functional aspects of binding of multiple substrate molecules to CYP3A4 we used resonance Raman and UV–VIS spectroscopy to document the effects of binding of synthetic testosterone dimers of different configurations, cis-TST2 and trans-TST2. We directly demonstrate that the binding …
Fluorescence Of Supported Phospholipid Bilayers Recorded In A Conventional Horizontal-Beam Spectrofluorometer, Elizaveta A. Kovrigina, Evgeni L. Kovrigin
Fluorescence Of Supported Phospholipid Bilayers Recorded In A Conventional Horizontal-Beam Spectrofluorometer, Elizaveta A. Kovrigina, Evgeni L. Kovrigin
Chemistry Faculty Research and Publications
Supported phospholipid bilayers are a convenient model of cellular membranes in studies of membrane biophysics and protein-lipid interactions. Traditionally, supported lipid bilayers are formed on a flat surface of a glass slide to be observed through fluorescence microscopes. This paper describes a method to enable fluorescence detection from the supported lipid bilayers using standard horizontal-beam spectrofluorometers instead of the microscopes. In the proposed approach, the supported lipid bilayers are formed on the inner optical surfaces of the standard fluorescence microcell. To enable observation of the bilayer absorbed on the cell wall, the microcell is placed in a standard fluorometer cell …
Influence Of Rtil Nanodomains On The Voltammetry And Spectroelectrochemistry Of Fullerene C60 In Benzonitrile/Room Temperature Ionic Liquids Mixtures, Abderrahman Atifi, Michael D. Ryan
Influence Of Rtil Nanodomains On The Voltammetry And Spectroelectrochemistry Of Fullerene C60 In Benzonitrile/Room Temperature Ionic Liquids Mixtures, Abderrahman Atifi, Michael D. Ryan
Chemistry Faculty Research and Publications
The cyclic voltammetry of fullerene C60 was examined in mixed benzonitrile/RTIL solvents in order to probe the effect of nanodomains in the mixed RTIL/benzonitrile solutions and their effect upon the voltammetry. In probing the interactions of the fullerides (up to C603−) with RTILs, BMIm+ (1-butyl-3-methylimidazolium, mostly planar) and tetraalkylammonium (more spherical/flexible) salts were used. In order to investigate these shifts in more detail, the ΔE12° (=E°1–E°2) and ΔE23° (=E°2–E°3) values, which were independent of the reference potential, were used. At higher concentrations of …
Reactivity Of Acyclic (Pentadienyl)Iron(1+) Cations With Phosphonate Stabilized Nucleophiles: Application To The Synthesis Of Oxygenated Metabolites Of Carvone, Do W. Lee, Charles Felix Manful, Jayapal Reddy Gone, Yuzhi Ma, William Donaldson
Reactivity Of Acyclic (Pentadienyl)Iron(1+) Cations With Phosphonate Stabilized Nucleophiles: Application To The Synthesis Of Oxygenated Metabolites Of Carvone, Do W. Lee, Charles Felix Manful, Jayapal Reddy Gone, Yuzhi Ma, William Donaldson
Chemistry Faculty Research and Publications
The addition of phosphonate stabilized carbon nucleophiles to acyclic (pentadienyl)iron(1+) cations proceeds predominantly at an internal carbon to afford (pentenediyl)iron complexes. Those complexes bearing an electron withdrawing group at the σ-bound carbon (i.e., 13/14) are stable and isolable, while complexes which do not contain an electron withdrawing group at the σ-bound carbon undergo CO insertion, reductive elimination and conjugation of the double bond to afford cyclohexenone products (21/22). Deprotonation of the phosphonate 13/14 or 21 and reaction with paraformaldehyde affords the olefinated products. This methodology was utilized to prepare oxygenated carvone metabolites (±)-25 and (±)-26.
Recent Advances In Development And Applications Of The Mixed Quantum/Classical Theory For Inelastic Scattering, Dmitri Babikov, Alexander Semenov
Recent Advances In Development And Applications Of The Mixed Quantum/Classical Theory For Inelastic Scattering, Dmitri Babikov, Alexander Semenov
Chemistry Faculty Research and Publications
A mixed quantum/classical approach to inelastic scattering (MQCT) is developed in which the relative motion of two collision partners is treated classically, and the rotational and vibrational motion of each molecule is treated quantum mechanically. The cases of molecule + atom and molecule + molecule are considered including diatomics, symmetric-top rotors, and asymmetric-top rotor molecules. Phase information is taken into consideration, permitting calculations of elastic and inelastic, total and differential cross sections for excitation and quenching. The method is numerically efficient and intrinsically parallel. The scaling law of MQCT is favorable, which enables calculations at high collision energies and for …
One-Pot Synthesis Of Biocompatible Silver Nanoparticle Composites From Cellulose And Keratin: Characterization And Antimicrobial Activity, Chieu D. Tran, Franja Prosenc, Mladen Franko, Gerald Benzi
One-Pot Synthesis Of Biocompatible Silver Nanoparticle Composites From Cellulose And Keratin: Characterization And Antimicrobial Activity, Chieu D. Tran, Franja Prosenc, Mladen Franko, Gerald Benzi
Chemistry Faculty Research and Publications
A novel, simple method was developed to synthesize biocompatible composites containing 50% cellulose (CEL) and 50% keratin (KER) and silver in the form of either ionic (Ag+) or Ag0 nanoparticles (Ag+NPs or Ag0NPs). In this method, butylmethylimmidazolium chloride ([BMIm+Cl–]), a simple ionic liquid, was used as the sole solvent and silver chloride was added to the [BMIm+Cl–] solution of [CEL+KER] during the dissolution process. The silver in the composites can be maintained as ionic silver (Ag+) or completely converted to metallic silver (Ag …
Accessing Spin-Crossover Behaviour In Iron(Ii) Complexes Of N-Confused Scorpionate Ligands, James R. Gardinier, Alexander Richard Treleven, Kristin J. Meise, Sergey Lindeman
Accessing Spin-Crossover Behaviour In Iron(Ii) Complexes Of N-Confused Scorpionate Ligands, James R. Gardinier, Alexander Richard Treleven, Kristin J. Meise, Sergey Lindeman
Chemistry Faculty Research and Publications
The first examples of a class of N-confused tris(pyrazolyl)methane ‘scorpionate’ ligands have been prepared. The magnetic properties of their iron(II) tetrafluoroborate complexes are dictated by changing one substituent per ligand rather than three as is typical for normal scorpionate ligands.
Reactivity Of (3-Methylpentadienyl)Iron(1+) Cation: Late-Stage Introduction Of A (3-Methyl-2z,4-Pentadien-1-Yl) Side Chain, Subhabrata Chaudhury, Shukun Li, William A. Donaldson
Reactivity Of (3-Methylpentadienyl)Iron(1+) Cation: Late-Stage Introduction Of A (3-Methyl-2z,4-Pentadien-1-Yl) Side Chain, Subhabrata Chaudhury, Shukun Li, William A. Donaldson
Chemistry Faculty Research and Publications
The 3-methyl-2Z,4-pentadien-1-yl sidechain is found in various sesquiterpenes and diterpenes. A route for the late stage introduction of this functionality was developed which relies on nucleophilic attack on the (3-methylpentadienyl)iron(1+) cation, followed by oxidative decomplexation. This methodology was applied to the synthesis of the proposed structure of heteroscyphic acid A methyl ester. Realization of this synthesis led to a correction of the proposed structure.
A Full-Dimensional Model Of Ozone Forming Reaction: The Absolute Value Of The Recombination Rate Coefficient, Its Pressure And Temperature Dependencies, Alexander Teplukhin, Dmitri Babikov
A Full-Dimensional Model Of Ozone Forming Reaction: The Absolute Value Of The Recombination Rate Coefficient, Its Pressure And Temperature Dependencies, Alexander Teplukhin, Dmitri Babikov
Chemistry Faculty Research and Publications
Rigorous calculations of scattering resonances in ozone are carried out for a broad range of rotational excitations. The accurate potential energy surface of Dawes is adopted, and a new efficient method for calculations of ro–vibrational energies, wave functions and resonance lifetimes is employed (which uses hyper-spherical coordinates, the sequential diagonalization/truncation approach, grid optimization and complex absorbing potential). A detailed analysis is carried out to characterize distributions of resonance energies and lifetimes, their rotational/vibrational content and their positions with respect to the centrifugal barrier. Emphasis is on the contribution of these resonances to the recombination process that forms ozone. It is …
Does Koopmans’ Paradigm For 1-Electron Oxidation Always Hold? Breakdown Of Ip/EOx Relationship For P-Hydroquinone Ethers And The Role Of Methoxy Group Rotation, Marat R. Talipov, Anitha Boddeda, Sergey V. Lindeman, Rajendra Rathore
Does Koopmans’ Paradigm For 1-Electron Oxidation Always Hold? Breakdown Of Ip/EOx Relationship For P-Hydroquinone Ethers And The Role Of Methoxy Group Rotation, Marat R. Talipov, Anitha Boddeda, Sergey V. Lindeman, Rajendra Rathore
Chemistry Faculty Research and Publications
Koopmans’ paradigm states that electron loss occurs from HOMO, thus forming the basis for the observed linear relationships between HOMO/IP, HOMO/Eox, and IP/Eox. In cases where a molecule undergoes dramatic structural reorganization upon 1-electron oxidation, the IP/Eoxrelationship does not hold, and the origin of which is not understood. For example, X-ray crystallography of the neutral and cation radicals of bicyclo[2.2.1]heptane-annulated p-hydroquinone ethers (THE and MHE) showed that they undergo electron-transfer-induced conformational reorganization and show breakdown of the IP/Eox relationship. DFT calculations revealed that Koopmans’ paradigm …
From Wires To Cables: Attempted Synthesis Of 1,3,5-Trifluorenylcyclohexane As A Platform For Molecular Cables, Marat R. Talipov, Sameh H. Abdelwahed, Khushabu Thakur, Scott Reid, Rajendra Rathore
From Wires To Cables: Attempted Synthesis Of 1,3,5-Trifluorenylcyclohexane As A Platform For Molecular Cables, Marat R. Talipov, Sameh H. Abdelwahed, Khushabu Thakur, Scott Reid, Rajendra Rathore
Chemistry Faculty Research and Publications
Multiple molecular wires braided together in a single assembly, termed as molecular cable, are promising next-generation materials for effective long-range charge transport. As an example of the platform for constructing molecular cables, 1,3,5-trifluorenylcyclohexane (TFC) and its difluorenyl analogues (DFCs) were systematically investigated both experimentally (X-ray crystallography) and theoretically (DFT calculations). Although the syntheses of DFCs were successfully achieved, the synthesis of TFC, which involved a similar intramolecular Friedel–Crafts cyclization as the last step, was unsuccessful. An exhaustive study of the conformational landscape of cyclohexane ring of TFC and DFCs revealed that TFC is …
A Search For Blues Brothers: X-Ray Crystallographic/Spectroscopic Characterization Of The Tetraarylbenzidine Cation Radical As A Product Of Aging Of Solid Magic Blue, Marat R. Talipov, Mohammad M. Hossain, Anitha Boddeda, Khushabu Thakur, Rajendra Rathore
A Search For Blues Brothers: X-Ray Crystallographic/Spectroscopic Characterization Of The Tetraarylbenzidine Cation Radical As A Product Of Aging Of Solid Magic Blue, Marat R. Talipov, Mohammad M. Hossain, Anitha Boddeda, Khushabu Thakur, Rajendra Rathore
Chemistry Faculty Research and Publications
Magic blue (MB+˙ SbCl6− salt), i.e. tris-4-bromophenylamminium cation radical, is a routinely employed one-electron oxidant that slowly decomposes in the solid state upon storage to form so called ‘blues brothers’, which often complicate the quantitative analyses of the oxidation processes. Herein, we disclose the identity of the main ‘blues brother’ as the cation radical and dication of tetrakis-(4-bromophenyl)benzidine (TAB) by a combined DFT and experimental approach, including isolation of TAB+˙ SbCl6− and its X-ray crystallography characterization. The formation of TAB in aged magic blue samples occurs by a Scholl-type …
X-Ray Structure And Properties Of The Ferrous Octaethylporphyrin Nitroxyl Complex, Nagabhushanam Kundakarla, Sergey V. Lindeman, Hafiz Md. Rahman, Michael D. Ryan
X-Ray Structure And Properties Of The Ferrous Octaethylporphyrin Nitroxyl Complex, Nagabhushanam Kundakarla, Sergey V. Lindeman, Hafiz Md. Rahman, Michael D. Ryan
Chemistry Faculty Research and Publications
The preparation and characterization of the iron octaethylporphyrin nitroxyl ion, [Fe(OEP)(NO)−], is reported. The complex was synthesized by the one-electron reduction of Fe(OEP)(NO) using anthracenide as the reducing agent. The compound was isolated as the potassium (2.2.2)cryptand salt. The anion was characterized using X-ray analysis with visible and infrared spectroscopy. The spectral features of the iron nitroxyl complex were consistent with previous literature reports. The important structural changes upon reduction were a significant decrease in the Fe–N–O bond angle from 142° to 127° and an increase in the N–O bond length from that in the starting nitrosyl moiety. …
Hydrogen-Atom Attack On Phenol And Toluene Is Ortho-Directed, Olha Krechkivska, Callan M. Wilcox, Tyler P. Troy, Klaas Nauta, Bun Chan, Rebecca Jacob, Scott A. Reid, Leo Radom, Timothy W. Schmidt, Scott H. Kable
Hydrogen-Atom Attack On Phenol And Toluene Is Ortho-Directed, Olha Krechkivska, Callan M. Wilcox, Tyler P. Troy, Klaas Nauta, Bun Chan, Rebecca Jacob, Scott A. Reid, Leo Radom, Timothy W. Schmidt, Scott H. Kable
Chemistry Faculty Research and Publications
The reaction of H + phenol and H/D + toluene has been studied in a supersonic expansion after electric discharge. The (1 + 1′) resonance-enhanced multiphoton ionization (REMPI) spectra of the reaction products, at m/z = parent + 1, or parent + 2 amu, were measured by scanning the first (resonance) laser. The resulting spectra are highly structured. Ionization energies were measured by scanning the second (ionization) laser, while the first laser was tuned to a specific transition. Theoretical calculations, benchmarked to the well-studied H + benzene → cyclohexadienyl radical reaction, were performed. The spectrum arising from the …
Design And Synthesis Of Oxazoline-Based Scaffolds For Hybrid Lewis Acid/Lewis Base Catalysis Of Carbon–Carbon Bond Formation, Dennis Wiedenhoeft, Adam R. Benoit, Jacob D. Porter, Yibiao Wu, Rajdeep S. Virdi, Alaa Shanaa, Chris Dockendorff
Design And Synthesis Of Oxazoline-Based Scaffolds For Hybrid Lewis Acid/Lewis Base Catalysis Of Carbon–Carbon Bond Formation, Dennis Wiedenhoeft, Adam R. Benoit, Jacob D. Porter, Yibiao Wu, Rajdeep S. Virdi, Alaa Shanaa, Chris Dockendorff
Chemistry Faculty Research and Publications
A new class of hybrid Lewis acid/Lewis base catalysts has been designed and prepared with an initial objective of promoting stereoselective direct aldol reactions. Several scaffolds were synthesized that contain amine moieties capable of enamine catalysis, connected to heterocyclic metal-chelating sections composed of an oxazole–oxazoline or thiazole–oxazoline. Early screening results have identified oxazole–oxazoline-based systems capable of promoting a highly diastereo- and enantioselective direct aldol reaction of propionaldehyde with 4-nitrobenzaldehyde, when combined with Lewis acids such as zinc triflate.
Inelastic Scattering Of Identical Molecules Within Framework Of The Mixed Quantum/Classical Theory: Application To Rotational Excitations In H2 + H2, Alexander Semenov, Dmitri Babikov
Inelastic Scattering Of Identical Molecules Within Framework Of The Mixed Quantum/Classical Theory: Application To Rotational Excitations In H2 + H2, Alexander Semenov, Dmitri Babikov
Chemistry Faculty Research and Publications
Theoretical foundation is laid out for description of permutation symmetry in the inelastic scattering processes that involve collisions of two identical molecules, within the framework of the mixed quantum/classical theory (MQCT). In this approach, the rotational (and vibrational) states of two molecules are treated quantum-mechanically, whereas their translational motion (responsible for scattering) is treated classically. This theory is applied to H2 + H2 system, and the state-to-state transition cross sections are compared versus those obtained from the full-quantum calculations and experimental results from the literature. Good agreement is found in all cases. It is also found that results of MQCT, …