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Articles 421 - 450 of 690
Full-Text Articles in Chemistry
Flame-Retarded Polystyrene: Investigating Chemical Interactions Between Ammonium Polyphosphate And Mgal Layered Double Hydroxide, Calistor Nyambo, Everson Kandare, Dongyan Wang, Charles A. Wilkie
Flame-Retarded Polystyrene: Investigating Chemical Interactions Between Ammonium Polyphosphate And Mgal Layered Double Hydroxide, Calistor Nyambo, Everson Kandare, Dongyan Wang, Charles A. Wilkie
Chemistry Faculty Research and Publications
Potential flame retardants, MgAl-LDH and ammonium polyphosphate (APP), were added to neat polystyrene (PS) individually or in combinations at weight fractions no greater than 10%. Structural morphologies of MgAl-LDH and the corresponding PS nanocomposites were established via X-ray diffraction (XRD) and transmission electron microscopy (TEM). Thermogravimetric analysis (TGA) and cone calorimetry were used to study the thermal stability and fire performance of the composites. Time to ignition is greatly reduced for PS composites when compared to the virgin polymer. Synergistic effects were observed in both TGA and cone calorimetry for formulations containing both MgAl-LDH and APP. Physical and chemical interactions …
Global Conformational Dynamics In Ras, Casey O'Connor, Evgenii L. Kovrigin
Global Conformational Dynamics In Ras, Casey O'Connor, Evgenii L. Kovrigin
Chemistry Faculty Research and Publications
Ras and its homologues are central to regulation of a multitude of cellular processes. Ras in complex with GTP binds and activates its downstream signaling partners. 31P NMR studies indicated that the Ras−GTP conformation is heterogeneous on a millisecond time scale, but details of its conformational dynamics remain unknown. Here we present evidence that the conformational exchange process in human H-Ras complexed with GTP mimic GppNHp is global, encompassing most of the GTPase catalytic domain. The correlated character of conformational dynamics in Ras opens opportunities for understanding allosteric effects in Ras function.
2,9-Bis(1,3-BenzothiaZol-2-Yl)-1,10-Phenanthroline DichloroMethane Disolvate, Jesmin Akther, Sergey V. Lindeman, Mohammad Rezaul Karim
2,9-Bis(1,3-BenzothiaZol-2-Yl)-1,10-Phenanthroline DichloroMethane Disolvate, Jesmin Akther, Sergey V. Lindeman, Mohammad Rezaul Karim
Chemistry Faculty Research and Publications
In the title compound, C26H14N4S2·2CH2Cl2, the two pendant benzothiazole groups are slightly twisted with respect to the phenanthroline core [dihedral angles = 1.03 (7) and 9.05 (5)°]. Weak intermolecular C-HN and C-HCl interactions occur in the crystal structure.
Reactions Of Rhenium And Manganese Carbonyl Complexes With 1,8-Bis(Diphenylphosphino)Naphthalene: Ligand Chelation, C–H And C–P Bond-Cleavage Reactions, Shariff E. Kabir, Faruque Ahmed, Shishir Ghosh, Mohammad R. Hassan, Muhammad S. Islam, Ayesha Sharmin, Derek A. Tocher, Daniel T. Haworth, Sergey V. Lindeman, Tasneem Siddiquee, Dennis W. Bennett, Kenneth I. Hardcastle
Reactions Of Rhenium And Manganese Carbonyl Complexes With 1,8-Bis(Diphenylphosphino)Naphthalene: Ligand Chelation, C–H And C–P Bond-Cleavage Reactions, Shariff E. Kabir, Faruque Ahmed, Shishir Ghosh, Mohammad R. Hassan, Muhammad S. Islam, Ayesha Sharmin, Derek A. Tocher, Daniel T. Haworth, Sergey V. Lindeman, Tasneem Siddiquee, Dennis W. Bennett, Kenneth I. Hardcastle
Chemistry Faculty Research and Publications
Reaction of [Re2(CO)8(MeCN)2] with 1,8-bis(diphenylphosphino)naphthalene (dppn) afforded three mono-rhenium complexes fac-[Re(CO)3(κ1:η1-PPh2C10H6)(PPh2H)] (1), fac-[Re(CO)3{κ1:κ1:η1-(O)PPh2C10H6(O)PPh(C6H4)}] (2) and fac-[ReCl(CO)3(κ2-PPh2C10H6PPh2)] (3). Compounds 1–3 are formed by Re–Re bond cleavage and P–C and C–H bond activation of the dppn ligand. Each of these three …
Β-Diketonate, Β-Ketoiminate, And Β-Diiminate Complexes Of Difluoroboron, Felipe P. Macedo, Chengeto Gwengo, Sergey V. Lindeman, Mark D. Smith, James R. Gardinier
Β-Diketonate, Β-Ketoiminate, And Β-Diiminate Complexes Of Difluoroboron, Felipe P. Macedo, Chengeto Gwengo, Sergey V. Lindeman, Mark D. Smith, James R. Gardinier
Chemistry Faculty Research and Publications
A series of β-diketonate, keto(aryl)iminato, and β-bis(aryl)iminato complexes of difluoroboron, twenty in total, have been prepared to assess the impact of chelate ring and aniline substitution on the structural, electrochemical, and photophysical properties of these ubiquitous chelates. DFT (B3LYP/6-31G*) calculations supplemented the experimental results and both demonstrated that replacing oxygen with the more electron-donating aniline groups serves to only fine-tune the electronic properties because both the HOMO and LUMO energies are affected by such substitution. The electronic properties of all compounds are most greatly influenced by the nature of the substituents bound to the carbon portion of the chelate ring. …
Bis[(Dimethyl-Λ4-Sulfanylidene)Oxonium] Hexabromidotellurate(Iv) Dimethyl Sulfoxide Disolvate, Martin D. Rudd, Gregory Kokke, Sergey V. Lindeman
Bis[(Dimethyl-Λ4-Sulfanylidene)Oxonium] Hexabromidotellurate(Iv) Dimethyl Sulfoxide Disolvate, Martin D. Rudd, Gregory Kokke, Sergey V. Lindeman
Chemistry Faculty Research and Publications
No abstract provided.
Formation Of Bicyclic Pyrroles From The Catalytic Coupling Reaction Of 2,5-Disubstituted Pyrroles With Terminal Alkynes, Involving The Activation Of Multiple C-H Bonds, Chase S. Yi, Jie Zhang
Formation Of Bicyclic Pyrroles From The Catalytic Coupling Reaction Of 2,5-Disubstituted Pyrroles With Terminal Alkynes, Involving The Activation Of Multiple C-H Bonds, Chase S. Yi, Jie Zhang
Chemistry Faculty Research and Publications
Substituted bicyclic pyrroles are produced directly from the coupling reaction of 2,5-disubstituted pyrroles with terminal alkynes, involving the activation of multiple C–H bonds and regioselective cyclisation.
Dirhenium Carbonyl Complexes Bearing 2-Vinylpyridine, Morpholine And 1-Methylimidazole Ligands, Shariff E. Kabir, Faruque Ahmed, Anamika Das, Mohammad R. Hassan, Daniel T. Haworth, Sergey V. Lindeman, Tasneem Siddiquee, Dennis W. Bennett
Dirhenium Carbonyl Complexes Bearing 2-Vinylpyridine, Morpholine And 1-Methylimidazole Ligands, Shariff E. Kabir, Faruque Ahmed, Anamika Das, Mohammad R. Hassan, Daniel T. Haworth, Sergey V. Lindeman, Tasneem Siddiquee, Dennis W. Bennett
Chemistry Faculty Research and Publications
Treatment of the labile compound [Re2(CO)8(MeCN)2] with 2-vinylpyridine in refluxing benzene affords exclusively the new compound [Re2(CO)8(μ-η1:η2-NC5H4CHCH2)] (1) in 39% yield in which the μ-η1:η2-vinylpyridine ligand is coordinated to one Re atom through the nitrogen and to the other Re atom via the olefinic double bond. Reaction of [Re2(CO)8(MeCN)2] with morpholine in refluxing benzene furnishes two compounds, [Re2(CO)9(η1-NC4H9O)] …
Thermal Stability And Degradation Kinetics Of Polystyrene/Organically-Modified Montmorillonite Nanocomposites, Grace Chigwada, Everson Kandare, Dongyan Wang, Stephen Majoni, Darlington Mlambo, Charles A. Wilkie, Jeanne M. Hossenlopp
Thermal Stability And Degradation Kinetics Of Polystyrene/Organically-Modified Montmorillonite Nanocomposites, Grace Chigwada, Everson Kandare, Dongyan Wang, Stephen Majoni, Darlington Mlambo, Charles A. Wilkie, Jeanne M. Hossenlopp
Chemistry Faculty Research and Publications
Organically-modified montmorillonite (MMT) clays have been prepared using ammonium salts containing quinoline, pyridine, benzene, and styrenic groups. The nanocomposites were prepared by melt blending and the formation of nanocomposites was characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Thermal stability and flammability were evaluated by thermogravimetric analysis (TGA) and cone calorimetry measurements, respectively. The presence ofmodified MMT at 5% loading resulted in significant improvement in thermal stability compared to the virgin polymer. Effective activation energies for mass loss were determined via a model-free isoconversional approach from TGA data obtained under N2 and under air. The additives served …
Chiral Ionic Liquids: Synthesis, Properties, And Enantiomeric Recognition, Shaofang Yu, Sergey V. Lindeman, Chieu D. Tran
Chiral Ionic Liquids: Synthesis, Properties, And Enantiomeric Recognition, Shaofang Yu, Sergey V. Lindeman, Chieu D. Tran
Chemistry Faculty Research and Publications
We have synthesized a series of structurally novel chiral ionic liquids which have a either chiral cation, chiral anion, or both. Cations are an imidazolium group, while anions are based on a borate ion with spiral structure and chiral substituents. Both (or all) stereoisomeric forms of each compound in the series can be readily synthesized in optically pure form by a simple one-step process from commercially available reagents. In addition to the ease of preparation, most of the chiral ILs in this series are liquid at room temperature with a solid to liquid transformation temperature as low as −70 °C …
Reactivity Of (2-Alkenyl-3-Pentene-1,5-Diyl)Iron Complexes: Preparation Of Functionalized Vinylcyclopropanes And Cycloheptadienes, Rajesh K. Pandey, Lizhu Wang, Nathaniel J Wallock, Sergey V. Lindeman, William A. Donaldson
Reactivity Of (2-Alkenyl-3-Pentene-1,5-Diyl)Iron Complexes: Preparation Of Functionalized Vinylcyclopropanes And Cycloheptadienes, Rajesh K. Pandey, Lizhu Wang, Nathaniel J Wallock, Sergey V. Lindeman, William A. Donaldson
Chemistry Faculty Research and Publications
The reactivity of (2-alkenyl-3-pentene-1,5-diyl)iron complexes toward olefin metathesis, cycloaddition, and mild oxidations (MnO2 or mCPBA) was examined. Cycloaddition reactions were observed to occur with modest diastereoselectivity (33−63% de). Decomplexation of the (3-pentenediyl) ligand may be accomplished by oxidation with either CAN or alkaline hydrogen peroxide to afford vinylcyclopropanecarboxylates or divinylcyclopropanecarboxylates. Reduction of the latter, followed by Cope rearrangement generates cycloheptadienylmethanols. These studies demonstrate that (2-alkenyl-3-pentene-1,5-diyl)iron complexes can serve as organometallic scaffolds for the preparation of a wide variety of structural motifs containing up to 5 contiguous stereocenters.
Double Carbon−Hydrogen Activation Of 2-Vinylpyridine: Synthesis Of Tri- And Pentanuclear Clusters Containing The Μ-Nc5H4Ch═C Ligand, Kazi A. Azam, Dennis W. Bennett, Mohammad R. Hassan, Daniel T. Haworth, Graeme Hogarth, Shariff E. Kabir, Sergey V. Lindeman, Luca Salassa, Sultana R. Simi, Tasneem Siddiquee
Double Carbon−Hydrogen Activation Of 2-Vinylpyridine: Synthesis Of Tri- And Pentanuclear Clusters Containing The Μ-Nc5H4Ch═C Ligand, Kazi A. Azam, Dennis W. Bennett, Mohammad R. Hassan, Daniel T. Haworth, Graeme Hogarth, Shariff E. Kabir, Sergey V. Lindeman, Luca Salassa, Sultana R. Simi, Tasneem Siddiquee
Chemistry Faculty Research and Publications
Reactions of 2-vinylpyridine with the triruthenium complexes [Ru3(CO)12] and [Ru3(CO)10(μ-dppm)] leads to a previously unknown double carbon−hydrogen bond activation of the β-carbon of the vinyl group to afford the pentaruthenium and triruthenium complexes [Ru5(CO)14(μ4-C5H4CH═C)(μ-H)2] (1) and [Ru3Cl(CO)5(μ-CO)(μ-dppm)(μ3-NC5H4CH═C)(μ-H)] (2), respectively. Crystal structures reveal two different forms of bridging of the dimetalated 2-vinylpyridyl ligand, capping a square face in 1 and a triangular face in 2.
Isolation And X-Ray Structural Characterization Of Tetraisopropylpyrene Cation Radical, Moloy Banerjee, Vijay Vyas, Sergey V. Lindeman, Rajendra Rathore
Isolation And X-Ray Structural Characterization Of Tetraisopropylpyrene Cation Radical, Moloy Banerjee, Vijay Vyas, Sergey V. Lindeman, Rajendra Rathore
Chemistry Faculty Research and Publications
A practical synthesis of 1,3,6,8-tetraisopropylpyrene and the isolation and X-ray structural characterization of its monomeric cation radical salt are described.
Aluminum-Containing Layered Double Hydroxides: The Thermal, Mechanical, And Fire Properties Of (Nano)Composites Of Poly(Methyl Methacrylate), Charles Manzi-Nshuti, Dongyan Wang, Jeanne Hossenlopp, Charles A. Wilkie
Aluminum-Containing Layered Double Hydroxides: The Thermal, Mechanical, And Fire Properties Of (Nano)Composites Of Poly(Methyl Methacrylate), Charles Manzi-Nshuti, Dongyan Wang, Jeanne Hossenlopp, Charles A. Wilkie
Chemistry Faculty Research and Publications
Hydrotalcite-like anionic clays or layered double hydroxides (LDHs) of the general formula, [MII1-xMIIIx(OH)2]intra[(CH2=CH(CH2)8COO-)x•nH2O]inter, with MIII = Al and MII = Co, Ni, Cu, and Zn, have been prepared by the co-precipitation method and used to prepare nanocomposites with poly(methyl methacrylate) (PMMA). One goal of this work was to compare the morphology, thermal, fire and mechanical properties with those of the well known PMMA–montmorillonite system. The thermal properties of these systems are greatly …
Het Acid Based Oligoesters – Tga/Ftir Studies, Thangamani Rajkumar, Chinnaswamy Thangavel Vijayakumar, Palanichamy Sivasamy, Charles A. Wilkie
Het Acid Based Oligoesters – Tga/Ftir Studies, Thangamani Rajkumar, Chinnaswamy Thangavel Vijayakumar, Palanichamy Sivasamy, Charles A. Wilkie
Chemistry Faculty Research and Publications
One of the important reactive halogenated dicarboxylic acids used in the synthesis of flame retardant unsaturated polyester resins is 1,4,5,6,7,7-hexachlorobicyclo [2.2.1] hept-5-ene-2,3-dicarboxylic acid (HET acid). In the present investigation four different oligoesters are synthesized using HET acid as the diacid component and 1,2-ethane diol, 1,2-propane diol, 1,3-propane diol and 1,4-butane diol as the aliphatic diols. Melt condensation technique in vacuum is used for the synthesis of the oligoesters. The number average molecular weights of the oligoesters are determined using end group analysis. The degree of polymerization is estimated to be 3–5. The structural characterization is done using FTIR and NMR …
Polymerically Modified Layered Silicates: An Effective Route To Nanocomposites, Jinguo Zhang, Evangelos Manias, Charles A. Wilkie
Polymerically Modified Layered Silicates: An Effective Route To Nanocomposites, Jinguo Zhang, Evangelos Manias, Charles A. Wilkie
Chemistry Faculty Research and Publications
Polymer/clay nanocomposites have been under an extensive investigation for about 15 years. Traditional methods to modify the clay are usually limited to small organic cations, preferably containing long alkyl chain(s), which are exchanged with the inorganic cations in the clay gallery. This article provides a comprehensive review on the strategies for clay modification using polymeric surfactants or polycations: from the synthesis of such surfactants, through the preparation of the polymerically modified clays, and to the fabrication of the respective polymer nanocomposites and their properties.
Synthesis, Electronic Properties, And X-Ray Structural Characterization Of Tetrarylbenzo[1,2-B:4,5-B′]Difuran Cation Radicals, Ruchi Shukla, Shriya Wadumethrige, Sergey V. Lindeman, Rajendra Rathore
Synthesis, Electronic Properties, And X-Ray Structural Characterization Of Tetrarylbenzo[1,2-B:4,5-B′]Difuran Cation Radicals, Ruchi Shukla, Shriya Wadumethrige, Sergey V. Lindeman, Rajendra Rathore
Chemistry Faculty Research and Publications
Electroactive tetraarylbenzo[1,2-b:4,5-b′]difuran (BDF) and model diarylbenzofuran derivatives are synthesized and their structures are established by X-ray crystallography. Isolation and X-ray crystallographic characterization of the robust cation-radical salts of BDF derivatives confirm that a single charge in the BDFs is stabilized largely by the benzodifuran and coplanar α-aryl groups lying on the longitudinal axis. These findings suggest that the linear arrays of BDFs may allow the construction of molecular wires suitable for long-range electron transport.
Kinetic, Spectroscopic, And X-Ray Crystallographic Evidence For The Cooperative Mechanism Of The Hydration Of Nitriles Catalyzed By A Tetranuclear Ruthenium-Μ-Oxo-Μ-Hydroxo Complex, Chae S. Yi, Tonya N. Zeczycki, Sergey V. Lindeman
Kinetic, Spectroscopic, And X-Ray Crystallographic Evidence For The Cooperative Mechanism Of The Hydration Of Nitriles Catalyzed By A Tetranuclear Ruthenium-Μ-Oxo-Μ-Hydroxo Complex, Chae S. Yi, Tonya N. Zeczycki, Sergey V. Lindeman
Chemistry Faculty Research and Publications
The tetranuclear ruthenium-oxo-hydroxo-hydride complex {[(PCy3)(CO)RuH]4(μ4-O)(μ3-OH)(μ2-OH)} (1) was found to be a highly cooperative catalyst for the nitrile hydration reaction. The cooperative mechanism of the hydration of benzonitrile was established by Hill inhibition kinetics. The treatment of a nitrile substrate with complex 1 led to the catalytically relevant nitrile-coordinated tetraruthenium complex 3. The X-ray structure of the nitrile-coordinated complex 3 showed a considerably “relaxed” tetrameric core structure compared to that of 1. The hydration of para-substituted benzonitriles p-X-C6H4CN with an electron-withdrawing …
A Second-Generation Janus Scorpionate Ligand: Controlling Coordination Modes In Iron(Ii) Complexes By Steric Modulation, Rosalice M. Silva, Chengeto Gwengo, Sergey V. Lindeman, Mark D. Smith, Gary J. Long, Fernande Grandjean, James R. Gardinier
A Second-Generation Janus Scorpionate Ligand: Controlling Coordination Modes In Iron(Ii) Complexes By Steric Modulation, Rosalice M. Silva, Chengeto Gwengo, Sergey V. Lindeman, Mark D. Smith, Gary J. Long, Fernande Grandjean, James R. Gardinier
Chemistry Faculty Research and Publications
The second-generation Janus scorpionate ligand [HB(mtdaMe)3−] containing methyl-mercaptothiadiazolyl (mtdaMe) heterocyclic rings and (N,N,N-) and (S,S,S-) binding pockets has been prepared. The effect of methyl substitution versus the unsubstituted first-generation Janus scorpionate [HB(mtda)3]− on the coordination chemistry with alkali metals and on the binding preferences and on the ground spin state of iron(II) complexes has been studied structurally and by 57Fe Mossbauer Spectroscopy.
Synthesis Of Cyclopropanes Via Organoiron Methodology: Preparation Of Rac-Dysibetaine Cpa, Tasneem A. Siddiquee, Julie Lukesh, Sergey Sergey Lindeman, William A. Donaldson
Synthesis Of Cyclopropanes Via Organoiron Methodology: Preparation Of Rac-Dysibetaine Cpa, Tasneem A. Siddiquee, Julie Lukesh, Sergey Sergey Lindeman, William A. Donaldson
Chemistry Faculty Research and Publications
The cyclopropane containing betaine, rac-dysibetaine CPa, was prepared from (1-methoxycarbonylpentadienyl)-Fe(CO)2PPh3+ by nucleophilic addition of nitromethane anion followed by oxidatively induced reductive elimination.
Benzimidazolium Surfactants For Modification Of Clays For Use With Styrenic Polymers, Marius C. Costache, Matthew Heidecker, Evangelos Manias, Rakesh K. Gupta, Charles A. Wilkie
Benzimidazolium Surfactants For Modification Of Clays For Use With Styrenic Polymers, Marius C. Costache, Matthew Heidecker, Evangelos Manias, Rakesh K. Gupta, Charles A. Wilkie
Chemistry Faculty Research and Publications
Nanocomposites of polystyrene (PS), acrylonitrile-butadiene-styrene copolymer (ABS) and high impact polystyrene (HIPS) were prepared with two new homologous benzimidazolium surfactants used as organic modifications for the clays. The morphology of the polymer/clay hybrids was evaluated by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM), showing good overall dispersion of the clay. The thermal stability of the polymer/clay nanocomposites was enhanced, as evaluated by thermogravimetric analysis. From cone calorimetric measurements, the peak heat release rate of the nanocomposites was decreased by about the same amount as seen for other organically-modified, commercially available clays.
Generation Of Molecular Complexity From Cyclooctatetraene: Synthesis Of A Protected 2-(3′-Carboxy-2′-Benzoylcyclopentyl)Glycine, Subhabrata Chaudhury, Sergey V. Lindeman, William A. Donaldson
Generation Of Molecular Complexity From Cyclooctatetraene: Synthesis Of A Protected 2-(3′-Carboxy-2′-Benzoylcyclopentyl)Glycine, Subhabrata Chaudhury, Sergey V. Lindeman, William A. Donaldson
Chemistry Faculty Research and Publications
Synthesis of a protected 2-(3′-carboxycyclopentyl)glycine rac-11, possessing four contiguous chiral carbons, was accomplished in six steps (20% yield) from the hydrocarbon cyclooctatetraene.
Revealing Nano-Confinement In Degradation And Relaxation Studies Of Two Structurally Different Polystyrene-Clay Systems, Kai Chen, Charles A. Wilkie, Sergey Vyazovkin
Revealing Nano-Confinement In Degradation And Relaxation Studies Of Two Structurally Different Polystyrene-Clay Systems, Kai Chen, Charles A. Wilkie, Sergey Vyazovkin
Chemistry Faculty Research and Publications
Degradation and relaxation studies have been performed on two polystyrene (PS)−montmorillonite clay nanocomposites, one of which has an intercalated PS−clay structure and the other an exfoliated PS−clay brush structure. Compared to virgin PS, both nanostructured materials have demonstrated the following similarities: (a) a high yield of α-methylstyrene in the degradation products as measured by infrared spectroscopy; (b) larger values of the activation energy of the thermal degradation as determined by isoconversional kinetic analysis of thermogravimetric data; and (c) larger values of the activation energy for the glass transition as found from the frequency dependence of the glass transition temperature measured …
Ferrocene And Ferrocenium Modified Clays And Their Styrene And Eva Composites, Charles Manzi-Nshuti, Charles A. Wilkie
Ferrocene And Ferrocenium Modified Clays And Their Styrene And Eva Composites, Charles Manzi-Nshuti, Charles A. Wilkie
Chemistry Faculty Research and Publications
In this work, ferrocene- and ferrocenium-containing salts were employed to modify montmorillonite. X-ray measurements show an increase in the interlayer spacing upon clay modification, which means that the larger and more organophilic cations were inserted into the gallery space of montmorillonite. Attempts to prepare nanocomposites of polystyrene and ethylene vinyl acetate copolymers lead to immiscible systems; the morphology of these systems was elucidated with TEM, XRD and cone calorimetry. The thermal stability of the composites is greater than that of the virgin polymer.
Reactivity Of [Re2(Co)8(Mecn)2] With Thiazoles: Hydrido Bridged Dirhenium Compounds Bearing Thiazoles In Different Coordination Modes, Shariff E. Kabir, Faruque Ahmed, Anamika Das, Mohammad R. Hassan, Daniel T. Haworth, Sergey V. Lindeman, G. M. Golzar Hossain, Tasneem Siddiquee, Dennis W. Bennett
Reactivity Of [Re2(Co)8(Mecn)2] With Thiazoles: Hydrido Bridged Dirhenium Compounds Bearing Thiazoles In Different Coordination Modes, Shariff E. Kabir, Faruque Ahmed, Anamika Das, Mohammad R. Hassan, Daniel T. Haworth, Sergey V. Lindeman, G. M. Golzar Hossain, Tasneem Siddiquee, Dennis W. Bennett
Chemistry Faculty Research and Publications
Reactions of the labile compound [Re2(CO)8(MeCN)2] with thiazole and 4-methylthiazole in refluxing benzene afforded the new compounds [Re2(CO)7{μ-2,3-η2-C3H(R)NS}{η1-NC3H2(4-R)S}(μ-H)] (1, R = H; 2, R = CH3), [Re2(CO)6{μ-2,3-η2-C3H(R)NS}{η1-NC3H2(4-R)S}2(μ-H)] (3, R = H; 4, R = CH3) and fac-[Re(CO)3(Cl){η1-NC3H2(4-R)S}2] (5, R = H; …
P–C And C–H Bond Cleavages Of Dppm In The Thermal Reaction Of [Ru3(Co)10(Μ-Dppm)] With Benzothiophene: X-Ray Structures Of [Ru6(Μ-Co)(Co)13{Μ4-Php(C6H4)Pph}(Μ6-C)] And [Ru4(Co)9(Μ3-Η2-Phpch2Pph2)(Μ4-Η6:Η1:Η1-C6H4)(Μ-H)], Shariff E. Kabir, Mohammad R. Hassan, Daniel T. Haworth, Sergey V. Lindeman, Tasneem Siddiquee, Dennis W. Bennett
P–C And C–H Bond Cleavages Of Dppm In The Thermal Reaction Of [Ru3(Co)10(Μ-Dppm)] With Benzothiophene: X-Ray Structures Of [Ru6(Μ-Co)(Co)13{Μ4-Php(C6H4)Pph}(Μ6-C)] And [Ru4(Co)9(Μ3-Η2-Phpch2Pph2)(Μ4-Η6:Η1:Η1-C6H4)(Μ-H)], Shariff E. Kabir, Mohammad R. Hassan, Daniel T. Haworth, Sergey V. Lindeman, Tasneem Siddiquee, Dennis W. Bennett
Chemistry Faculty Research and Publications
The thermal reaction of [Ru3(CO)10(μ-dppm)] (1) with benzothiophene in refluxing toluene gives a complex mixture of products. These include the known compounds [Ru2(CO)6{μ-CH2PPh(C6H4)PPh}] (2), [Ru2(CO)6{μ-C6H4PPh(CH2)PPh}] (3), [Ru3(CO)9{μ3-η3-(Ph)PCH2P(Ph)C6H4}] (4) and [Ru3(CO)10{μ-η2-PPh(CH2)(C6H4)PPh}] (6), as well as the new clusters [Ru6(μ-CO)(CO) …
Mechanism Of Rate-Limiting Motions In Enzyme Function, Eric D. Watt, Hiroko Shimada, Evgenii L. Kovrigin, J. Patrick Loria
Mechanism Of Rate-Limiting Motions In Enzyme Function, Eric D. Watt, Hiroko Shimada, Evgenii L. Kovrigin, J. Patrick Loria
Chemistry Faculty Research and Publications
The ability to use conformational flexibility is a hallmark of enzyme function. Here we show that protein motions and catalytic activity in a RNase are coupled and display identical solvent isotope effects. Solution NMR relaxation experiments identify a cluster of residues, some distant from the active site, that are integral to this motion. These studies implicate a single residue, histidine-48, as the key modulator in coupling protein motion with enzyme function. Mutation of H48 to alanine results in loss of protein motion in the isotope-sensitive region of the enzyme. In addition, k cat decreases for this mutant and the kinetic …
The Voltammetric Study Of The Reduction Of Tetraalkylammonium Perchlorate By Fe(Tpp)2-, Chathra Shirani De Silva, Michael D. Ryan
The Voltammetric Study Of The Reduction Of Tetraalkylammonium Perchlorate By Fe(Tpp)2-, Chathra Shirani De Silva, Michael D. Ryan
Chemistry Faculty Research and Publications
Tetraalkylammonium ions react with Fe(TPP)2− to form Fe(TPP)(R)− and trialkylamine. The tetrabutylammonium cation was verified to be the source of the alkyl group in the product, Fe(TPP)(R)−, by using (1H5C2)3(2H5C2)N− as the cation and 2H NMR. The reaction of Fe(TPP)2− with Bu4N− was monitored by cyclic voltammetry and thin layer spectroelectrochemistry. The activation parameters were measured, and were most consistent with an electron transfer (ET) mechanism. The rate of the reaction of tetramethyl and tetraethylammonium ions with Fe(TPP) …
Synthesis And Characterization Of Platinum – Selenium Derivatives: X-Ray Structure Of Trans-Pt(Pet3)2(Seph)2, Martin D. Rudd, Sergey V. Lindeman
Synthesis And Characterization Of Platinum – Selenium Derivatives: X-Ray Structure Of Trans-Pt(Pet3)2(Seph)2, Martin D. Rudd, Sergey V. Lindeman
Chemistry Faculty Research and Publications
The crystal structure of trans-[((bis)triethylphosphine)(bis(phenylselenato))platinum (II)] has been determined by single crystal X-ray diffraction. Crystallization occurs in the triclinic space group P-1 (No. 2) with a = 8.9964(2) Å, b = 11.5103(2) Å, c = 14.9335(3) Å; α = 85.8750(10)°, β = 72.5350(10)°, γ = 68.4450(10)°. Details of the structure and spectroscopic results are presented and discussed and comparisons are made with related square planar platinum (II) structures.
Unraveling The Catalytic Mechanism Of Nitrile Hydratases, Sanghamitra Mitra, Richard C. Holz
Unraveling The Catalytic Mechanism Of Nitrile Hydratases, Sanghamitra Mitra, Richard C. Holz
Chemistry Faculty Research and Publications
To elucidate a detailed catalytic mechanism for nitrile hydratases (NHases), the pH and temperature dependence of the kinetic constants kcat and Km for the cobalt-type NHase from Pseudonocardia thermophila JCM 3095 (PtNHase) were examined. PtNHase was found to exhibit a bell-shaped curve for plots of relative activity versus pH at pH 3.2–11 and was found to display maximal activity between pH 7.2 and 7.8. Fits of these data provided pKES1 and pKES2 values of 5.9 ± 0.1 and 9.2 ± 0.1 (kcat′ = 130 ± 1 …