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Articles 541 - 570 of 1105
Full-Text Articles in Chemistry
A Versatile Synthesis Of Electroactive Stilbenoprismands For Effective Binding Of Metal Cations, Sergey V. Lindeman, Rajendra Rathore, Paromita Debroy
A Versatile Synthesis Of Electroactive Stilbenoprismands For Effective Binding Of Metal Cations, Sergey V. Lindeman, Rajendra Rathore, Paromita Debroy
Chemistry Faculty Research and Publications
A versatile synthesis of a new class of polyaromatic receptors (stilbenoprismands) containing a Δ-shaped cavity similar to that of the π-prismand together with an intimately coupled electroactive stilbenoid moiety was accomplished via an efficient intramolecular McMurry coupling reaction. The presence of the Δ-shaped cavity in stilbenoprismands allows an efficient binding of a single silver cation as probed by 1H NMR spectroscopy. Electron-rich stilbenoprismands undergo a ready oxidation to their highly robust cation−radical and dicationic salts. X-ray structure determination of a representative dicationic stilbenoprismand showed that the charges were largely localized on the tetraarylethylene moiety, which results in a twisting …
Octamethoxydibenzochrysene: Isolation And X-Ray Crystallographic Characterization Of A Twisted Polyaromatic Cation Radical, Tushar Navale, Linyi Zhai, Sergey V. Lindeman, Rajendra Rathore
Octamethoxydibenzochrysene: Isolation And X-Ray Crystallographic Characterization Of A Twisted Polyaromatic Cation Radical, Tushar Navale, Linyi Zhai, Sergey V. Lindeman, Rajendra Rathore
Chemistry Faculty Research and Publications
The isolation and X-ray crystal structure determination of octamethoxydibenzochrysene (3) cation radical together with DFT calculations allow us to delineate evidence that the complex structural changes (i.e. elongation and shortening of various bonds) in a polyaromatic hydrocarbon can be predicted based on the positioning of the largest bonding and antibonding character of the HOMO.
Terphenyl Crowns: A New Family Of Receptors Containing Ethereal Canopies That Direct Potassium Cation Onto Benzenoid Platforms For Cation–Π Interactions, Ruchi Shukla, Sergey V. Lindeman, Rajendra Rathore
Terphenyl Crowns: A New Family Of Receptors Containing Ethereal Canopies That Direct Potassium Cation Onto Benzenoid Platforms For Cation–Π Interactions, Ruchi Shukla, Sergey V. Lindeman, Rajendra Rathore
Chemistry Faculty Research and Publications
We have synthesized three simple and versatile terphenyl crowns (TC) receptors containing ethereal canopies that direct a potassium cation for efficient cation–π interactions as established by 1H NMR spectroscopy and by isolation and X-ray crystallography of their K+ salts.
Substrate Induced Structural And Dynamics Changes In Human Phosphomevalonate Iinase And Implications For Mechanism, Andrew Lawrence Olson, Huili Yao, Timothy J. Herdendorf, Henry M. Miziorko, Supa Hannongbua, Patchareenat Saparpakom, Sheng Cai, Daniel S. Sem
Substrate Induced Structural And Dynamics Changes In Human Phosphomevalonate Iinase And Implications For Mechanism, Andrew Lawrence Olson, Huili Yao, Timothy J. Herdendorf, Henry M. Miziorko, Supa Hannongbua, Patchareenat Saparpakom, Sheng Cai, Daniel S. Sem
Chemistry Faculty Research and Publications
Phosphomevalonate kinase (PMK) catalyzes an essential step in the mevalonate pathway, which is the only pathway for synthesis of isoprenoids and steroids in humans. PMK catalyzes transfer of the γ-phosphate of ATP to mevalonate 5-phosphate (M5P) to form mevalonate 5-diphosphate. Bringing these phosphate groups in proximity to react is especially challenging, given the high negative charge density on the four phosphate groups in the active site. As such, conformational and dynamics changes needed to form the Michaelis complex are of mechanistic interest. Herein, we report the characterization of substrate induced changes (Mg-ADP, M5P, and the ternary complex) in PMK using …
Tetranuclear Group 7/8 Mixed-Metal And Open Trinuclear Group 7 Metal Carbonyl Clusters Bearing Bridging 2-Mercapto-1-Methylimidazole Ligands, Shishir Ghosh, Shariff E. Kabir, Salina Pervin, Arun K. Raha, G. M. Golzar Hossain, Daniel T. Haworth, Sergey V. Lindeman, Dennis W. Bennett, Tasneem Siddiquee, Luca Salassa, Herbert W. Roesky
Tetranuclear Group 7/8 Mixed-Metal And Open Trinuclear Group 7 Metal Carbonyl Clusters Bearing Bridging 2-Mercapto-1-Methylimidazole Ligands, Shishir Ghosh, Shariff E. Kabir, Salina Pervin, Arun K. Raha, G. M. Golzar Hossain, Daniel T. Haworth, Sergey V. Lindeman, Dennis W. Bennett, Tasneem Siddiquee, Luca Salassa, Herbert W. Roesky
Chemistry Faculty Research and Publications
The reactivity of group 7 metal dinuclear carbonyl complexes [M2(CO)6(μ-SN2C4H5)2] (1, M = Re; 2, M = Mn) toward group 8 metal trinuclear carbonyl clusters were examined. Reactions of 1 and 2 with [Os3(CO)10(NCMe)2] in refluxing benzene furnished the tetranuclear mixed-metal clusters [Os3Re(CO)13(μ3-SN2C4H5)] (3) and [Os3Mn(CO)13(μ3-SN2C4H5)] (4), respectively. Similar treatment of …
Molecular Motion And Performance Enhancement Of Borazan Fluorescent Dyes, Tyler James Morin, Sergey V. Lindeman, James R. Gardinier
Molecular Motion And Performance Enhancement Of Borazan Fluorescent Dyes, Tyler James Morin, Sergey V. Lindeman, James R. Gardinier
Chemistry Faculty Research and Publications
The preparation of three 2,6-dipyrazolyl-4-X-anilines, H(pz2AnX) (X = p-CF3, Cl, tBu) using CuI-catalyzed amination is described. Subsequent reactions of H(pz2AnX) with triphenylboron proceeds with benzene elimination to give the corresponding Ph2B(pz2AnX) compounds in high yields. The Ph2B(pz2AnX) are more highly emissive in the solid state than the previously reported BORAZAN fluorophores, Ph2B(pzAnX), their monopyrazolyl counterparts. As with the Ph2B(pzAnX), the color of emission in Ph2B(pz2 …
13c-Methyl Isocyanide As An Nmr Probe For Cytochrome P450 Active Site, Christopher R Mccullough, Phani Kumar Pullela, Sang-Choul Im, Lucy Waskell, Daniel S. Sem
13c-Methyl Isocyanide As An Nmr Probe For Cytochrome P450 Active Site, Christopher R Mccullough, Phani Kumar Pullela, Sang-Choul Im, Lucy Waskell, Daniel S. Sem
Chemistry Faculty Research and Publications
The cytochromes P450 (CYPs) play a central role in many biologically important oxidation reactions, including the metabolism of drugs and other xenobiotic compounds. Because they are often assayed as both drug targets and anti-targets, any tools that provide: (a) confirmation of active site binding and (b) structural data, would be of great utility, especially if data could be obtained in reasonably high throughput. To this end, we have developed an analog of the promiscuous heme ligand, cyanide,with a 13CH3-reporter attached. This 13C-methyl isocyanide ligand binds to bacterial (P450cam) and membrane-bound mammalian (CYP2B4) CYPs. It can be …
Resonance Raman Characterization Of The Peroxo And Hydroperoxo Intermediates In Cytochrome P450, Ilia G. Denisov, Piotr J. Mak, Thomas M. Makris, Stephen G. Sligar, James R. Kincaid
Resonance Raman Characterization Of The Peroxo And Hydroperoxo Intermediates In Cytochrome P450, Ilia G. Denisov, Piotr J. Mak, Thomas M. Makris, Stephen G. Sligar, James R. Kincaid
Chemistry Faculty Research and Publications
Resonance Raman (RR) studies of intermediates generated by cryoreduction of the oxyferrous complex of the D251N mutant of cytochrome P450cam (CYP101) are reported. Owing to the fact that proton delivery to the active site is hindered in this mutant, the unprotonated peroxo-ferric intermediate is observed as the primary species after radiolytic reduction of the oxy-complex in frozen solutions at 77 K. In as much as previous EPR and ENDOR studies have shown that annealing of this species to ∼180 K results in protonation of the distal oxygen atom to form the hydroperoxo intermediate, this system has been exploited to …
Resonance Raman Interrogation Of The Consequences Of Heme Rotational Disorder In Myoglobin And Its Ligated Derivatives, Freeborn Rwere, Piotr J. Mak, James R. Kincaid
Resonance Raman Interrogation Of The Consequences Of Heme Rotational Disorder In Myoglobin And Its Ligated Derivatives, Freeborn Rwere, Piotr J. Mak, James R. Kincaid
Chemistry Faculty Research and Publications
Resonance Raman spectroscopy is employed to characterize heme site structural changes arising from conformational heterogeneity in deoxyMb and ligated derivatives, i.e., the ferrous CO (MbCO) and ferric cyanide (MbCN) complexes. The spectra for the reversed forms of these derivatives have been extracted from the spectra of reconstituted samples. Dramatic changes in the low-frequency spectra are observed, where newly observed RR modes of the reversed forms are assigned using protohemes that are selectively deuterated at the four methyl groups or at the four methine carbons. Interestingly, while substantial changes in the disposition of the peripheral vinyl and propionate groups can be …
Analyzing The Catalytic Role Of Asp97 In The Methionine Aminopeptidase From Escherichia Coli, Sanghamitra Mitra, Kathleen M. Job, Lu Meng, Brian Bennett, Richard C. Holz
Analyzing The Catalytic Role Of Asp97 In The Methionine Aminopeptidase From Escherichia Coli, Sanghamitra Mitra, Kathleen M. Job, Lu Meng, Brian Bennett, Richard C. Holz
Physics Faculty Research and Publications
An active site aspartate residue, Asp97, in the methionine aminopeptidase (MetAPs) from Escherichia coli (EcMetAP-I) was mutated to alanine, glutamate, and asparagine. Asp97 is the lone carboxylate residue bound to the crystallographically determined second metal-binding site in EcMetAP-I. These mutant EcMetAP-I enzymes have been kinetically and spectroscopically characterized. Inductively coupled plasma–atomic emission spectroscopy analysis revealed that 1.0 ± 0.1 equivalents of cobalt were associated with each of the Asp97-mutated EcMetAP-Is. The effect on activity after altering Asp97 to alanine, glutamate or asparagine is, in general, due to a ∼ 9000-fold decrease in kca towards …
Analyzing The Catalytic Mechanism Of The Fe-Type Nitrile Hydratase From Comamonas Testosteroni Ni1, Saroja Rao, Richard C. Holz
Analyzing The Catalytic Mechanism Of The Fe-Type Nitrile Hydratase From Comamonas Testosteroni Ni1, Saroja Rao, Richard C. Holz
Chemistry Faculty Research and Publications
In order to gain insight into the catalytic mechanism of Fe-type nitrile hydratases (NHase), the pH and temperature dependence of the kinetic parameters kcat, Km, and kcat/Km along with the solvent isotope effect were examined for the Fe-type NHase from Comamonas testosteroni Ni1 (CtNHase). CtNHase was found to exhibit a bell-shaped curve for plots of relative activity vs pH over pH values 4−10 for the hydration of acrylonitrile and was found to display maximal activity at pH ∼7.2. Fits of these data provided a pKES1 value of …
Defining Resonance Raman Spectral Responses To Substrate Binding By Cytochrome P450 From Pseudomonas Putida, Piotr J. Mak, Daniel Kaluka, Munyaradzi Edith Manyumwa, Haiqing Zhang, Tianjing Deng, James R. Kincaid
Defining Resonance Raman Spectral Responses To Substrate Binding By Cytochrome P450 From Pseudomonas Putida, Piotr J. Mak, Daniel Kaluka, Munyaradzi Edith Manyumwa, Haiqing Zhang, Tianjing Deng, James R. Kincaid
Chemistry Faculty Research and Publications
Resonance Raman spectra are reported for substrate-free and camphor-bound cytochrome P450cam and its isotopically labeled analogues that have been reconstituted with protoheme derivatives that bear -CD3 groups at the 1, 3, 5, and 8-positions (d12-protoheme) or deuterated methine carbons (d4-protoheme). In agreement with previous studies of this and similar enzymes, substrate binding induces changes in the high frequency and low frequency spectral regions, with the most dramatic effect in the low frequency region being activation of a new mode near 367 cm−1. This substrate-activated mode had been previously assigned as a second “propionate bending” mode (Chen et …
Fire Retardancy Of Melamine And Zinc Aluminum Layered Double Hydroxide In Poly(Methyl Methacrylate), Charles Manzi-Nshuti, Jeanne Hossenlopp, Charles Wilkie
Fire Retardancy Of Melamine And Zinc Aluminum Layered Double Hydroxide In Poly(Methyl Methacrylate), Charles Manzi-Nshuti, Jeanne Hossenlopp, Charles Wilkie
Chemistry Faculty Research and Publications
The thermal and fire properties of PMMA modified with various loadings of melamine or zinc aluminum undecenoate LDH were evaluated using TGA, DTA and cone calorimetry. The additives were characterized by X-ray diffraction, TGA, FT-IR and elemental analysis. While the two additives are very effective with this polymer, a higher loading of melamine (30%) is required to reach a good reduction in PHRR (47%) relative to the pure polymer, while with the LDH, 10% loading is enough to obtain a similar reduction. The combinations of these additives in PMMA reveal that the time to PHRR and the amount of smoke …
Resonance Raman Spectroscopic Studies Of Hydroperoxo Derivatives Of Cobalt-Substituted Myoglobin, Piotr J. Mak, James R. Kincaid
Resonance Raman Spectroscopic Studies Of Hydroperoxo Derivatives Of Cobalt-Substituted Myoglobin, Piotr J. Mak, James R. Kincaid
Chemistry Faculty Research and Publications
Recent progress in generating and stabilizing reactive heme protein enzymatic intermediates by cryoradiolytic reduction has prompted application of a range of spectroscopic approaches to effectively interrogate these species. The impressive potential of resonance Raman spectroscopy for characterizing such samples has been recently demonstrated in a number of studies of peroxo- and hydroperoxo-intermediates. While it is anticipated that this approach can be productively applied to the wide range of heme proteins whose reaction cycles naturally involve these peroxo- and hydroperoxo-intermediates, one limitation that sometimes arises is the lack of enhancement of the key intraligand ν(O–O) stretching mode in the native …
Synthetic Studies Directed Toward Amphidinol 2: Elucidation Of The Relative Configuration Of The C1–C10 Fragment, Praveen Kommana, Seung Won Chung, William A. Donaldson
Synthetic Studies Directed Toward Amphidinol 2: Elucidation Of The Relative Configuration Of The C1–C10 Fragment, Praveen Kommana, Seung Won Chung, William A. Donaldson
Chemistry Faculty Research and Publications
Model compounds (11 and 12) for the C1–C10 tetrahydropyran fragment of amphidinol 2 were prepared from (2S)-benzyloxypropanal in 9 steps. The synthetic route relied on diastereoselective diene-aldehyde cycloaddition, stereoselective C-allylation, and reagent based enantioselective aldehyde allylation. Comparison of the NMR spectra for models 11 and 12 with that for amphidinol 2 indicated that the C1–C10 segment of the natural product possesses the 2R*,4R*,6R*,7S*,8R*,10S* relative configuration.
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.
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.
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.
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.
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 …