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Articles 361 - 390 of 690
Full-Text Articles in Chemistry
Affinity Capillary Electrophoretic Study Of K+/Na+ Selectivity Of Hexaarylbenzene-Based Polyaromatic Receptor, Sille Ehala, Rajendra Rathore, Emanuel Makrlik, Petr Toman, Václav Kašička
Affinity Capillary Electrophoretic Study Of K+/Na+ Selectivity Of Hexaarylbenzene-Based Polyaromatic Receptor, Sille Ehala, Rajendra Rathore, Emanuel Makrlik, Petr Toman, Václav Kašička
Chemistry Faculty Research and Publications
Affinity capillary electrophoretic (ACE) study has proved the selectivity of hexaarylbenzene-based polyaromatic receptor (R) for K+ ion over Na+ ion. The apparent binding constants of the R complexes with K+ and Na+ ions were determined from the dependence of effective electrophoretic mobility of R on the concentration of the above alkali metal ions in the background electrolyte using a non-linear regression analysis. The apparent binding constants (Kb) of the K-R+ and Na–R+ complexes in methanolic medium were evaluated as log Kb = 3.20 ± 0.22 for the K–R+ complex, and log Kb≅−0.7 for the Na–R+ complex.
Isomerization As A Key Path To Molecular Products In The Gas-Phase Decomposition Of Halons, Aimable Kalume, Lisa George, Scott A. Reid
Isomerization As A Key Path To Molecular Products In The Gas-Phase Decomposition Of Halons, Aimable Kalume, Lisa George, Scott A. Reid
Chemistry Faculty Research and Publications
The decomposition of halons remains controversial concerning the branching between radical and molecular products. The latter channel, where it has been found, is presumed to occur via a constrained symmetric multicenter transition state. Isomerization pathways in the gas-phase chemistry of halons have rarely been considered, despite the fact that the iso-halons, which feature a halogen−halogen bond, are widely recognized as important reactive intermediates in condensed phases. In this Letter, detailed calculations and modeling of the unimolecular decomposition of several important halons, including CF2Cl2, CF2Br2, and CHBr3, reveal that isomerization is …
Tricarbonylrhenium(I) And Manganese(I) Complexes Of 2-(Pyrazolyl)-4-Toluidine, Brendan J Liddle, Sarath Wanniarachchi, Sergey V. Lindeman, James R. Gardinier
Tricarbonylrhenium(I) And Manganese(I) Complexes Of 2-(Pyrazolyl)-4-Toluidine, Brendan J Liddle, Sarath Wanniarachchi, Sergey V. Lindeman, James R. Gardinier
Chemistry Faculty Research and Publications
A series of tricarbonyl rhenium(I) and manganese(I) complexes of the electroactive 2-(pyrazolyl)-4-toluidine ligand, H(pzAnMe), has been prepared and characterized including by single crystal X-ray diffraction studies. The reactions between H(pzAnMe) and M(CO)5Br afford fac-MBr(CO)3[H(pzAnMe)] (M = Mn, 1a; Re, 1b) complexes. The ionic species {fac-M(CH3CN)(CO)3[H(pzAnMe)]}(PF6) (M = Mn, 2a; Re, 2b) were prepared by metathesis of 1a or 1b with TlPF6 in acetonitrile. Complexes 1a and 1b partly ionize to {M(CH3CN)(CO)3[H(pzAnMe)]+ …
Breaking The Cycle: Impact Of Sterically-Tailored Tetra(Pyrazolyl)Lutidines On The Self-Assembly Of Silver(I) Complexes, Tyler James Morin, Andrew Merkel, Sergey V. Lindeman, James R. Gardinier
Breaking The Cycle: Impact Of Sterically-Tailored Tetra(Pyrazolyl)Lutidines On The Self-Assembly Of Silver(I) Complexes, Tyler James Morin, Andrew Merkel, Sergey V. Lindeman, James R. Gardinier
Chemistry Faculty Research and Publications
A improved preparation of the pentadentate ligand α,α,α′,α′-tetra(pyrazolyl)lutidine, pz4lut, and the syntheses of three new alkyl-substituted pyrazolyl derivatives pz4′4lut (pz4′ = 4-methylpyrazolyl), pz*4lut (pz* = 3,5-dimethylpyrazolyl), and pzDIP4lut (pzDIP = 3,5-diisopropylpyrazolyl) are described. The silver(I) complexes of these ligands were studied to ascertain the impact of pyrazolyl substitution, if any, on their binding modes and on solubility issues. In the solid state, [Ag(pz4lut)](BF4) (1), [Ag(pz4′4lut)](BF4) (2), and [Ag(pz*4lut)](BF4) (3 …
A Shortened Synthesis Of Optically Pure Tricarbonyl[Methyl (2e,4e)-6-Oxo-2,4-Hexadienoate]Iron Leading To Improved Yield, Rajesh K. Pandey, Sergey V. Lindeman, William A. Donaldson
A Shortened Synthesis Of Optically Pure Tricarbonyl[Methyl (2e,4e)-6-Oxo-2,4-Hexadienoate]Iron Leading To Improved Yield, Rajesh K. Pandey, Sergey V. Lindeman, William A. Donaldson
Chemistry Faculty Research and Publications
The (+)- and (–)-enantiomers of tricarbonyl[methyl (2E,4E)-6-oxo-2,4-hexadienoate]iron are prepared in 4 steps from commercially available hexadienal (26% and 25% yields, respectively).
Resin-Modified Glass-Ionomer Setting Reaction Competition, David W. Berzins, S. Abey, M. C. Costache, Charles A. Wilkie, H. W. Roberts
Resin-Modified Glass-Ionomer Setting Reaction Competition, David W. Berzins, S. Abey, M. C. Costache, Charles A. Wilkie, H. W. Roberts
Chemistry Faculty Research and Publications
Resin-modified glass ionomers (RMGI) set by at least 2 mechanisms dependent upon reactant diffusion prior to gelation. Each reaction’s kinetics and setting mechanism may rely on and/or compete with the other. In this study, we investigated RMGI setting reaction interactions using differential scanning calorimetry (DSC) by varying light-cure initiation times. A RMGI was analyzed with isothermal and dynamic temperature scan DSC with light-curing occurring immediately, or at 5 or 10 minutes after mixing as well as without light-activation. Results show that as time allowed for the acid-base reaction increased, the light-activation polymerization exotherm decreased. Conversely, analysis of DSC data suggests …
Anion Exchange Kinetics Of Nanodimensional Layered Metal Hydroxides: Use Of Isoconversional Analysis, Stephen Majoni, Jeanne Hossenlopp
Anion Exchange Kinetics Of Nanodimensional Layered Metal Hydroxides: Use Of Isoconversional Analysis, Stephen Majoni, Jeanne Hossenlopp
Chemistry Faculty Research and Publications
Anion exchange reactions of nanodimensional layered metal hydroxide compounds are utilized to create materials with targeted physical and chemical properties and also as a means for controlled release of intercalated anions. The kinetics of this important class of reaction are generally characterized by model-based approaches. In this work, a different approach based on isothermal, isoconversional analysis was utilized to determine effective activation energies with respect to extent of reaction. Two different layered metal hydroxide materials were chosen for reaction with chloride anions, using a temperature range of 30−60 °C. The concentrations of anions released into solution and the changes in …
Infrared Spectroelectrochemical Reduction Of Iron Porphyrin Complexes, Zhongcheng Wei, Michael D. Ryan
Infrared Spectroelectrochemical Reduction Of Iron Porphyrin Complexes, Zhongcheng Wei, Michael D. Ryan
Chemistry Faculty Research and Publications
The spectroelectrochemistry of iron porphinones and their nitrosyl complexes were examined by infrared spectroscopy, as well as ferrous octaethylporphyrin nitrosyl. With the use of d8-THF, the solvent was transparent down to 1200 cm−1. For the porphinones, the reduction of the macrocycle ring could be observed by the changes in the νCO band and, for the nitrosyl complex, the changes in the nitrosyl ligand were directly observable from the νNO band. Formation of the ferrous complexes led to a small downshift in the νCO band. Further reduction to the formal Fe(“I”) complex led to …
Thermal Degradation Studies On Pmma–Het Acid Based Oligoesters Blends, Thangamani Rajkumar, Chinnaswamy Thangavel Vijayakumar, Palanichamy Sivasamy, Bojja Sreedhar, Charles A. Wilkie
Thermal Degradation Studies On Pmma–Het Acid Based Oligoesters Blends, Thangamani Rajkumar, Chinnaswamy Thangavel Vijayakumar, Palanichamy Sivasamy, Bojja Sreedhar, Charles A. Wilkie
Chemistry Faculty Research and Publications
Imparting thermal stability to polymethyl methacrylate (PMMA) without affecting its optical clarity is attempted by incorporating HET acid based oligoesters. Pure PMMA and PMMA containing five and 20 wt% of four different oligoesters are separately prepared using bulk polymerization. The thermal properties of the materials studied using DSC, TG, TG–FTIR and Pyr–GC–MS are presented. The main volatile degradation products identified are CO, HCl, CO2, H2O, hexachlorocyclopentadiene, hexachloroendomethylene tetrahydrophthalic acid/anhydride and methyl methacrylate. A detailed mechanism for the influence of the degradation products of HET acid based oligoesters on the thermal degradation of PMMA is also presented.
Immobilization Of Motile Bacterial Cells Via Dip-Pen Nanolithography, Dorjderem Nyamjav, Sergey Rozhok, Richard C. Holz
Immobilization Of Motile Bacterial Cells Via Dip-Pen Nanolithography, Dorjderem Nyamjav, Sergey Rozhok, Richard C. Holz
Chemistry Faculty Research and Publications
A strategy to bind bacterial cells to surfaces in a directed fashion via dip-pen nanolithography (DPN) is presented. Cellular attachment to pre-designed DPN generated microarrays was found to be dependent on the shape and size of the surface feature. While this observation is likely due in part to a dense, well formed mercaptohexadecanoic acid (MHA) monolayer generated via DPN, it may also simply be due to the physical shape of the surface structure. Motile Pseudomonas aeruginosa bacterial cells were observed to bind to DPN generated mercaptohexadecanoic acid/poly-L-lysine (MHA/PLL) line patterns, 'blocks' made up of eight lines with 100 nm spacings, …
Isolation And X-Ray Structural Characterization Of A Dicationic Homotrimer Of 2,3,6,7-Tetramethoxy-9,10-Dimethylanthracene Cation Radical, Matthew J. Modjewski, Ruchi Shukla, Sergey V. Lindeman, Rajendra Rathore
Isolation And X-Ray Structural Characterization Of A Dicationic Homotrimer Of 2,3,6,7-Tetramethoxy-9,10-Dimethylanthracene Cation Radical, Matthew J. Modjewski, Ruchi Shukla, Sergey V. Lindeman, Rajendra Rathore
Chemistry Faculty Research and Publications
Electrochemical oxidation of 2,3,6,7-tetramethoxy-9,10-dimethylanthracene (1) showed that it undergoes a highly reversible electrochemical oxidation (Eox = 0.81 V vs SCE) and forms a modestly stable cation-radical salt in solution. X-ray crystallography established that 1+SbCl6- crystallizes as a (centrosymmetric) dicationic homotrimer via a close cofacial association of a pair of cationic and one neutral molecule of 1 with an interplanar separation of ∼3.2 Å. The structure of the dicationic homotrimer was also reproduced by DFT calculations. Furthermore, the structure of a dicationic spiro adduct, formed by a slow decomposition of a solution of 1+ …
Reactivity Of Phenyldi(2-Thienyl)Phosphine Towards Group 7 Metal Carbonyls: Carbon–Phosphorus Bond Activation, Shishir Ghosh, Alok K. Das, Noorjahan Begum, Daniel T. Haworth, Sergey V. Lindeman, James R. Gardinier, Tasneem A. Siddiquee, Dennis W. Bennett, Ebbe Nordlander, Graeme Hogarth, Shariff E. Kabir
Reactivity Of Phenyldi(2-Thienyl)Phosphine Towards Group 7 Metal Carbonyls: Carbon–Phosphorus Bond Activation, Shishir Ghosh, Alok K. Das, Noorjahan Begum, Daniel T. Haworth, Sergey V. Lindeman, James R. Gardinier, Tasneem A. Siddiquee, Dennis W. Bennett, Ebbe Nordlander, Graeme Hogarth, Shariff E. Kabir
Chemistry Faculty Research and Publications
Addition of phenyldi(2-thienyl)phosphine (PPhTh2) to [Re2(CO)10−n(NCMe)n] (n = 1, 2) affords the substitution products [Re2(CO)10−n(PhPTh2)n] (1, 2) together with small amounts of fac-[ClRe(CO)3(PPhTh2)2] (3) (n = 2). Reaction of [Re2(CO)10] with PPhTh2in refluxing xylene affords a mixture which includes 2, [Re2(CO)7(PPhTh2)(μ-PPhTh)(μ-H)] (4), [Re2(CO)7(PPhTh2)(μ-PPhTh)(μ-η1,κ1(S)-C4H3S)] (5) and …
Inhibitors Of Bacterial N-Succinyl-L,L-Diaminopimelic Acid Desuccinylase (Dape) And Demonstration Of In Vitro Antimicrobial Activity, Danuta Gillner, Nicola Armoush, Richard C. Holz, Daniel P. Becker
Inhibitors Of Bacterial N-Succinyl-L,L-Diaminopimelic Acid Desuccinylase (Dape) And Demonstration Of In Vitro Antimicrobial Activity, Danuta Gillner, Nicola Armoush, Richard C. Holz, Daniel P. Becker
Chemistry Faculty Research and Publications
The dapE-encoded N-succinyl-L,L-diaminopimelic acid desuccinylase (DapE) is a critical bacterial enzyme for the construction of the bacterial cell wall. A screen biased toward compounds containing zinc-binding groups (ZBG’s) including thiols, carboxylic acids, boronic acids, phosphonates and hydroxamates has delivered a number of micromolar inhibitors of DapE from Haemophilus influenzae, including the low micromolar inhibitor L-captopril (IC50 = 3.3 μM, Ki = 1.8 μM). In vitro antimicrobial activity was demonstrated for l-captopril against Escherichia coli.
Polymer Nanocomposites Using Zinc Aluminum And Magnesium Aluminum Oleate Layered Double Hydroxides: Effects Of The Polymeric Compatibilizer And Of Composition On The Thermal And Fire Properties Of Pp/Ldh Nanocomposites, Charles Manzi-Nshuti, Ponusa Songtipya, Evangelos Manias, Maria Del Mar Jimenez-Gasco, Jeanne Hossenlopp, Charles A. Wilkie
Polymer Nanocomposites Using Zinc Aluminum And Magnesium Aluminum Oleate Layered Double Hydroxides: Effects Of The Polymeric Compatibilizer And Of Composition On The Thermal And Fire Properties Of Pp/Ldh Nanocomposites, Charles Manzi-Nshuti, Ponusa Songtipya, Evangelos Manias, Maria Del Mar Jimenez-Gasco, Jeanne Hossenlopp, Charles A. Wilkie
Chemistry Faculty Research and Publications
A series of five oleate-containing layered double hydroxides with varied ratios of zinc to magnesium, i.e., with the general formula Zn2−yMgyAl(OH)6 [CH3(CH2)7CHCH(CH2)7COO]·nH2O, were synthesized and used to prepare nanocomposites of polypropylene (PP). The nanomaterials were characterized by elemental analysis, attenuated total reflection-infrared spectroscopy (ATR-IR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA), while the composites were characterized by XRD, TGA, transmission electron microscopy (TEM) and cone calorimetry. The zinc-containing LDH showed better dispersion in the polymer at the micrometer level …
The Effects Of Intralayer Metal Composition Of Layered Double Hydroxides On Glass Transition, Dispersion, Thermal And Fire Properties Of Their Pmma Nanocomposites, Charles Manzi-Nshuti, Dan Chen, Shengpei Su, Charles A. Wilkie
The Effects Of Intralayer Metal Composition Of Layered Double Hydroxides On Glass Transition, Dispersion, Thermal And Fire Properties Of Their Pmma Nanocomposites, Charles Manzi-Nshuti, Dan Chen, Shengpei Su, Charles A. Wilkie
Chemistry Faculty Research and Publications
A series of aluminum-containing layered double hydroxides (LDHs), containing Mg, Ca, Co, Ni, Cu and Zn as the divalent metals, have been prepared by the co-precipitation method and used to prepare nanocomposites of PMMA by in situ bulk polymerization. The additives were characterized by Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy (XRD) and thermogravimetric analysis while the polymer composites were characterized by XRD, transmission electron microscopy, differential scanning calorimetry and cone calorimetry. Polymerization of methyl methacrylate in the presence of these undecenoate LDHs results in composites with enhanced thermal stability. The glass transition temperatures of the composites and the pristine …
Scope And Mechanistic Investigations On The Solvent-Controlled Regio- And Stereoselective Formation Of Enol Esters From The Ruthenium-Catalyzed Coupling Reaction Of Terminal Alkynes And Carboxylic Acids, Chae S. Yi, Ruili Gao
Scope And Mechanistic Investigations On The Solvent-Controlled Regio- And Stereoselective Formation Of Enol Esters From The Ruthenium-Catalyzed Coupling Reaction Of Terminal Alkynes And Carboxylic Acids, Chae S. Yi, Ruili Gao
Chemistry Faculty Research and Publications
The ruthenium-hydride complex (PCy3)2(CO)RuHCl was found to be a highly effective catalyst for the alkyne-to-carboxylic acid coupling reaction to give synthetically useful enol ester products. A strong solvent effect was observed for the ruthenium catalyst in modulating the activity and selectivity; the coupling reaction in CH2Cl2 led to the regioselective formation of gem-enol ester products, while the stereoselective formation of (Z)-enol esters was obtained in THF. The coupling reaction was found to be strongly inhibited by PCy3. The coupling reaction of both PhCO2H/PhC≡CD and PhCO2 …
Manipulating Self-Assembly In Silver(I) Complexes Of 1,3-Di-N-Pyrazolylorganyls, Brendan J. Liddle, Daniel Hall, Sergey V. Lindeman, Mark D. Smith, James R. Gardinier
Manipulating Self-Assembly In Silver(I) Complexes Of 1,3-Di-N-Pyrazolylorganyls, Brendan J. Liddle, Daniel Hall, Sergey V. Lindeman, Mark D. Smith, James R. Gardinier
Chemistry Faculty Research and Publications
Three di-N-pyrazolylorganyls with different conformational flexibilities in the three-atom organyl spacers have been prepared, and the self-assembly properties with AgBF4 have been studied both in solution and in the solid state. All ligands give low-coordinate silver(I) centers that are capable of participating in multiple noncovalent interactions, but only the rigid 1,8-dipyrazolylnaphthalene ligand promotes very short Ag−Ag contacts.
Decarbonylation Reaction Of [Os3(Co)10(Μ-H)(Μ-Sn2C4H5)]: X-Ray Structures Of The Two Isomers Of [Os3(Co)9(Μ-H)(Μ3-Η2-Sn2C4H5)], Shishir Ghosh, Shariff E. Kabir, Mansura Khatun, Daniel T. Haworth, Sergey V. Lindeman, Tasneem Siddiquee, Dennis W. Bennett
Decarbonylation Reaction Of [Os3(Co)10(Μ-H)(Μ-Sn2C4H5)]: X-Ray Structures Of The Two Isomers Of [Os3(Co)9(Μ-H)(Μ3-Η2-Sn2C4H5)], Shishir Ghosh, Shariff E. Kabir, Mansura Khatun, Daniel T. Haworth, Sergey V. Lindeman, Tasneem Siddiquee, Dennis W. Bennett
Chemistry Faculty Research and Publications
The thermal reaction of [Os3(CO)10(μ-H)(μ-SN2C4H5)] (1) at 110 °C afforded the new compound [Os3(CO)9(μ-H)(μ 3-η 2-SN2C4H5)] (2) in 84% yield. Compound 2 exists as two isomers, which differ in the disposition of the bridging hydride ligand. Both of the isomers of 2 have been characterized by a combination of elemental analysis, infrared and 1H NMR spectroscopic data together with single crystal X-ray crystallography. The isomers …
Toward Charge-Neutral ‘Soft Scorpionates’: Coordination Chemistry And Lewis Acid Promoted Isomerization Of Tris(1-Organo-Imidazol-2-Ylthio)Methanes, Chengeto Gwengo, Rosalice M. Silva, Mark D. Smith, Sergey V. Lindeman, James R. Gardinier
Toward Charge-Neutral ‘Soft Scorpionates’: Coordination Chemistry And Lewis Acid Promoted Isomerization Of Tris(1-Organo-Imidazol-2-Ylthio)Methanes, Chengeto Gwengo, Rosalice M. Silva, Mark D. Smith, Sergey V. Lindeman, James R. Gardinier
Chemistry Faculty Research and Publications
Two tris(1-organo-imidazol-2-ylthio)methanes, HC(S-timR)3 (R = organo = methyl, tert-butyl), have been prepared by a triphasic reaction between chloroform, the appropriate heterocycle, and saturated aqueous solutions of Na2CO3, in the presence of a phase transfer agent, (NBu4)(Br). These ligands have been characterized both spectroscopically and by single crystal X-ray diffraction. The reaction chemistry of these potentially N,N,N-tripodal ligands with AgBF4 was also explored where simple 1:1 coordination complexes could be isolated from reactions performed in THF solution at room temperature. The derivative {Ag[HC(S-timMe)3]}(BF4) was structurally …
Activation Of Tri(2-Furyl)Phosphine At A Dirhenium Centre: Formation Of Phosphido-Bridged Dirhenium Complexes, Shishir Ghosh, Mansura Khatun, Daniel T. Haworth, Sergey V. Lindeman, Tasneem Siddiquee, Dennis W. Bennett, Graeme Hogarth, Ebbe Nordlander, Shariff E. Kabir
Activation Of Tri(2-Furyl)Phosphine At A Dirhenium Centre: Formation Of Phosphido-Bridged Dirhenium Complexes, Shishir Ghosh, Mansura Khatun, Daniel T. Haworth, Sergey V. Lindeman, Tasneem Siddiquee, Dennis W. Bennett, Graeme Hogarth, Ebbe Nordlander, Shariff E. Kabir
Chemistry Faculty Research and Publications
Reaction of tri(2-furyl)phosphine (PFu3) with [Re2(CO)10−n(NCMe)n] (n = 1, 2) at 40 °C gave the substituted complexes [Re2(CO)10−n(PFu3)n] (1 and 2), the phosphines occupying axial position in all cases. Heating [Re2(CO)10] and PFu3 in refluxing xylene also gives 1 and 2 together with four phosphido-bridged complexes; [Re2(CO)8−n(PFu3)n(μ-PFu2)(μ-H)] (n = 0, 1, 2) (3–5) and [Re2(CO)6 …
Structure - Property Relationships Of New Polystyrene Nanocomposites Prepared From Initiator-Containing Layered Double Hydroxides Of Zinc Aluminum And Magnesium Aluminum, Charles Manzi-Nshuti, Dan Chen, Shengpei Shu, Charles A. Wilkie
Structure - Property Relationships Of New Polystyrene Nanocomposites Prepared From Initiator-Containing Layered Double Hydroxides Of Zinc Aluminum And Magnesium Aluminum, Charles Manzi-Nshuti, Dan Chen, Shengpei Shu, Charles A. Wilkie
Chemistry Faculty Research and Publications
Polystyrene/layered double hydroxides (PS/LDHs) nanocomposites were prepared by free radical polymerization of styrene monomer in the presence of LDHs intercalated with 4,4′-azobis(4-cyanopentanoate) anions (LDH–ACPA). XRD and ATR-IR are used to confirm that the materials produced are layered and the presence of the azo-initiator anions in these LDHs. These LDHs were used successfully to polymerize styrene and both XRD and TEM images of the composites support the formation of a mixed exfoliated-intercalated nanocomposite for ZnAl–ACPA but a microcomposite for MgAl–ACPA. The magnesium-containing LDHs decreased the glass transition temperature (Tg) of the composites while ZnAl–ACPA did not affect T …
Regioselective Intermolecular Coupling Reaction Of Arylketones And Alkenes Involving C-H Bond Activation Catalyzed By An In Situ Formed Cationic Ruthenium-Hydride Complex, Chae S. Yi, Do W. Lee
Regioselective Intermolecular Coupling Reaction Of Arylketones And Alkenes Involving C-H Bond Activation Catalyzed By An In Situ Formed Cationic Ruthenium-Hydride Complex, Chae S. Yi, Do W. Lee
Chemistry Faculty Research and Publications
The cationic ruthenium hydride complex, formed in situ from the treatment of the tetranuclear ruthenium hydride complex {[(PCy3)(CO)RuH]4(μ4-O)(μ3-OH)(μ2-OH)} with HBF4·OEt2, was found to be a highly effective catalyst for the intermolecular coupling reaction of arylketones and 1-alkenes to give the substituted indene and ortho-C−H insertion products. The formation of the indene products resulted from the initial alkene isomerization followed by regioselective ortho-C−H insertion of 2-alkene and dehydrative cyclization. The preliminary mechanistic studies revealed a rapid and reversible ortho-C−H bond activation followed by the …
Recent Applications Of Acyclic (Diene)Iron Complexes And (Dienyl)Iron Cations In Organic Synthesis, William A. Donaldson, Subhabrata Chaudhury
Recent Applications Of Acyclic (Diene)Iron Complexes And (Dienyl)Iron Cations In Organic Synthesis, William A. Donaldson, Subhabrata Chaudhury
Chemistry Faculty Research and Publications
Complexation of (tricarbonyl)iron to an acyclic diene serves to protect the ligand against oxidation, reduction, and cycloaddition reactions, whereas the steric bulk of this adjunct serves to direct the approaches of reagents to unsaturated groups attached to the diene onto the face opposite to iron. Furthermore, the Fe(CO)3 moiety can serve to stabilize carbocation centers adjacent to the diene (i.e. pentadienyl-iron cations). Recent applications of these reactivities to the synthesis of polyene-, cyclopropane-, cycloheptadiene-, and cyclohexenone-containing natural products or analogues are presented.
Does Organic Modification Of Layered Double Hydroxides Improve The Fire Performance Of Pmma?, Calistor Nyambo, Dan Chen, Shengpei Shu, Charles A. Wilkie
Does Organic Modification Of Layered Double Hydroxides Improve The Fire Performance Of Pmma?, Calistor Nyambo, Dan Chen, Shengpei Shu, Charles A. Wilkie
Chemistry Faculty Research and Publications
The effect of modified layered double hydroxides (LDHs) on fire properties of poly(methyl methacrylate) is investigated. Organically-modified LDHs were prepared via rehydration of calcined hydrotalcite in a palmitate solution. Composites consisting of the organo-LDHs, unmodified hydrotalcite and calcined oxides were prepared with poly(methyl methacrylate) using melt blending. Thermal and fire properties of the (nano)composites were studied. The thermogravimetric analyses of the composites show an increase in thermal stability. Fire performance, evaluated using cone calorimetry, show that organically-modified LDHs composites give the best reductions in peak heat release rate, PHRR, i.e., 51% at 10% weight loading. Dispersion of the LDHs was …
Investigations Of 2-Thiazoline-2-Thiol As A Ligand: Synthesis And X-Ray Structures Of [Mn2(Co)7(Μ-Ns2C3H4)2] And [Mn(Co)3(Pph3)(Κ2-Ns2C3H4)], Shishir Ghosh, Faruque Ahmed, Rafique Al-Mamun, Daniel T. Haworth, Sergey V. Lindeman, Tasneem Siddiquee, Dennis W. Bennett, Shariff E. Kabir
Investigations Of 2-Thiazoline-2-Thiol As A Ligand: Synthesis And X-Ray Structures Of [Mn2(Co)7(Μ-Ns2C3H4)2] And [Mn(Co)3(Pph3)(Κ2-Ns2C3H4)], Shishir Ghosh, Faruque Ahmed, Rafique Al-Mamun, Daniel T. Haworth, Sergey V. Lindeman, Tasneem Siddiquee, Dennis W. Bennett, Shariff E. Kabir
Chemistry Faculty Research and Publications
Treatment of Mn2(CO)10 with 2-thiazoline-2-thiol in the presence of Me3NO at room temperature afforded the dimanganese complexes [Mn2(CO)7(μ-NS2C3H4)2] (1) and [Mn2(CO)6(μ-NS2C3H4)2] (2) in 51 and 34% yields, respectively. Compound 1 was quantitatively converted into 2 when reacted with one equiv of Me3NO. Reaction of 1 with triphenylphosphine at room temperature furnished the mononuclear complex [Mn(CO)3(PPh3)(κ 2 …
Polymer Nanocomposites Using Zinc Aluminum And Magnesium Aluminum Oleate Layered Double Hydroxides: Effects Of Ldh Divalent Metals On Dispersion, Thermal, Mechanical And Fire Performance In Various Polymers, Charles Manzi-Nshuti, Ponusa Songtipya, Evangelos Manias, Maria Del Mar Jimenez-Gasco, Jeanne Hossenlopp, Charles Wilkie
Polymer Nanocomposites Using Zinc Aluminum And Magnesium Aluminum Oleate Layered Double Hydroxides: Effects Of Ldh Divalent Metals On Dispersion, Thermal, Mechanical And Fire Performance In Various Polymers, Charles Manzi-Nshuti, Ponusa Songtipya, Evangelos Manias, Maria Del Mar Jimenez-Gasco, Jeanne Hossenlopp, Charles Wilkie
Chemistry Faculty Research and Publications
Oleate-containing layered double hydroxides of zinc aluminum (ZnAl) and magnesium aluminum (MgAl) were used to prepare nanocomposites of polyethylene, poly(ethylene-co-butyl acrylate) and poly(methyl methacrylate). The additives and/or their polymer composites were characterized by X-ray diffraction, FTIR, elemental analysis, thermogravimetric analysis, mechanical testing, and cone calorimetry. The unusual packing of the monounsaturated oleate anions in the gallery of these LDHs facilitates the dispersion of these nanomaterials. The inorganic LDH protects the polymer from thermal oxidation, shown by enhancement of the thermal and fire properties of the corresponding polymer nanocomposites. There is a qualitative difference in the morphology of the …
Fire Retardancy Of Bis[2-(Methacryloyloxy)Ethyl] Phosphate Modified Poly(Methyl Methacrylate) Nanocomposites Containing Layered Double Hydroxide And Montmorillonite, Linjiang Wang, Shengpei Shu, Dan Chen, Charles A. Wilkie
Fire Retardancy Of Bis[2-(Methacryloyloxy)Ethyl] Phosphate Modified Poly(Methyl Methacrylate) Nanocomposites Containing Layered Double Hydroxide And Montmorillonite, Linjiang Wang, Shengpei Shu, Dan Chen, Charles A. Wilkie
Chemistry Faculty Research and Publications
Copolymer nanocomposites were prepared by suspension copolymerization of bis[2-(methacryloyloxy)ethyl] phosphate and methyl methacrylate, together with bis(2-ethylhexyl) phosphate layered double hydroxide and a montmorillonite, Cloisite 93A. X-ray diffraction and transmission electron microscopy were used to characterize the morphology of nanocomposites and the dispersion of additives in the polymer. The thermal stability of the nanocomposites has been assessed by thermogravimetric analysis and cone calorimetry has been used to study the fire properties. Bis[2-(methacryloyloxy)ethyl] phosphate not only copolymerized with MMA, but also aids in the dispersion of additives in PMMA. The copolymer nanocomposites have better dispersion and higher degradation temperature and more char …
X-Ray Structural Characterization Of Charge Delocalization Onto The Three Equivalent Benzenoid Rings In Hexamethoxytriptycene Cation Radical, Vincent J. Chebny, Tushar S. Navale, Ruchi Shukla, Sergey V. Lindeman, Rajendra Rathore
X-Ray Structural Characterization Of Charge Delocalization Onto The Three Equivalent Benzenoid Rings In Hexamethoxytriptycene Cation Radical, Vincent J. Chebny, Tushar S. Navale, Ruchi Shukla, Sergey V. Lindeman, Rajendra Rathore
Chemistry Faculty Research and Publications
Definitive X-ray crystallographic evidence is obtained for a single hole (or a polaron) to be uniformly distributed on the three equivalent 1,2-dimethoxybenzenoid (or veratrole) rings in the hexamethoxytriptycene cation radical. This conclusion is further supported by electrochemical analysis and by the observation of an intense near-IR transition in its electronic spectrum, as well as by comparison of the spectral and electrochemical characteristics with the model compounds containing one and two dimethoxybenzene rings.
Linking Conformation Change To Hemoglobin Activation Via Chain-Selective Time-Resolved Resonance Raman Spectroscopy On Protoheme/Mesoheme Hybrids, Gurusamy Balakrishnan, Mohammed Ibrahim, Piotr J. Mak, Jessica Hata, James R. Kincaid, Thomas G. Spiro
Linking Conformation Change To Hemoglobin Activation Via Chain-Selective Time-Resolved Resonance Raman Spectroscopy On Protoheme/Mesoheme Hybrids, Gurusamy Balakrishnan, Mohammed Ibrahim, Piotr J. Mak, Jessica Hata, James R. Kincaid, Thomas G. Spiro
Chemistry Faculty Research and Publications
Time-resolved Resonance Raman spectra are reported for Hb tetramers, in which the αand β chains are selectively substituted with mesoheme. The Soret absorption band shift in meso- relative to protoheme permits chain-selective excitation of heme RR spectra. The evolution of these spectra following HbCO photolysis show that geminate recombination rates and yields are the same for the two chains, consistent with recent results on 15N-heme isotopomer hybrids. The spectra also reveal systematic shifts in the deoxy-heme ν4 and νFe-His) RR bands, which are anti-correlated. These shifts are resolved for the successive intermediates in the protein structure, which have previously been …
Analyzing The Binding Of Co(Ii)-Specific Inhibitors To The Methionyl Aminopeptidases From Escherichia Coli And Pyrococcus Furiosus, Sanghamitra Mitra, George Sheppard, Jieyi Wang, Brian Bennett, Richard C. Holz
Analyzing The Binding Of Co(Ii)-Specific Inhibitors To The Methionyl Aminopeptidases From Escherichia Coli And Pyrococcus Furiosus, Sanghamitra Mitra, George Sheppard, Jieyi Wang, Brian Bennett, Richard C. Holz
Chemistry Faculty Research and Publications
Methionine aminopeptidases (MetAPs) represent a unique class of protease that is capable of the hydrolytic removal of an N-terminal methionine residue from nascent polypeptide chains. MetAPs are physiologically important enzymes; hence, there is considerable interest in developing inhibitors that can be used as antiangiogenic and antimicrobial agents. A detailed kinetic and spectroscopic study has been performed to probe the binding of a triazole-based inhibitor and a bestatin-based inhibitor to both Mn(II)- and Co(II)-loaded type-I (Escherichia coli) and type-II (Pyrococcus furiosus) MetAPs. Both inhibitors were found to be moderate competitive inhibitors. The triazole-type inhibitor was found to …