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Full-Text Articles in Chemistry

Synthesis And Characterization Of Conjugated/Cross-Conjugated Benzene-Bridged Boron Difluoride Formazanate Dimers, Stephanie M. Barbon, Jacquelyn T. Price, Umesh Yogarajah, Joe Gilroy Jun 2015

Synthesis And Characterization Of Conjugated/Cross-Conjugated Benzene-Bridged Boron Difluoride Formazanate Dimers, Stephanie M. Barbon, Jacquelyn T. Price, Umesh Yogarajah, Joe Gilroy

Chemistry Publications

One of the most common strategies for the production of molecular materials with optical properties in the far-red/near-IR regions of the electromagnetic spectrum is their incorporation into dimeric architectures. In this paper, we describe the synthesis and characterization (1H, 11B, 13C and 19F NMR spectroscopy, IR and UV-Vis absorption and emission spectroscopy, mass spectrometry and X-ray crystallography) of the first examples of boron difluoride (BF2) formazanate dimers. Specifically, the properties of meta- and para-substituted benzene-bridged dimers p-10 and m-10 were compared to closely related boron difluoride triphenyl formazanate complex …

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Synthesis Of Tetrahydro-1,2-Oxazines And Pyrrolidines Via Cycloadditions Of Donor-Acceptor Cyclobutanes And Nitrosoarenes, Naresh Vemula, Brian L Pagenkopf Jun 2015

Synthesis Of Tetrahydro-1,2-Oxazines And Pyrrolidines Via Cycloadditions Of Donor-Acceptor Cyclobutanes And Nitrosoarenes, Naresh Vemula, Brian L Pagenkopf

Chemistry Publications

During efforts to expand the scope of Lewis-acid-catalyzed [4+2] cycloaddition between donor–acceptor cyclobutanes and nitrosoarenes, an unexpected formation of pyrrolidine products was discovered when 50 mol-% of MgI2 was used as a Lewis acid. It was also observed that the electronics of the nitrosoarene and judicious selection of the Lewis acid catalyst have a profound effect on the regioselectivity of the reaction.

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The Effect Of Extended Π-Conjugation On The Spectroscopic And Electrochemical Properties Of Boron Difluoride Formazanate Complexes, Stephanie M. Barbon, Viktor N. Staroverov, Joe Gilroy May 2015

The Effect Of Extended Π-Conjugation On The Spectroscopic And Electrochemical Properties Of Boron Difluoride Formazanate Complexes, Stephanie M. Barbon, Viktor N. Staroverov, Joe Gilroy

Chemistry Publications

The effect of extended π-conjugation on the spectroscopic and electrochemical properties of boron difluoride (BF2) formazanate complexes was studied by the systematic comparison of phenyl- and naphthyl-substituted derivatives. Each of the BF2 complexes described was characterized by 1H, 13C, 11B and 19F NMR spectroscopy, cyclic voltammetry, infrared spectroscopy, UV-vis absorption and emission spectroscopy and mass spectrometry. X-ray crystallography and electronic structure calculations were used to rationalize the trends observed, including direct comparison of 3-cyano-, 3-nitro- and 3-phenyl-substituted BF2 formazanate complexes. In all cases, the wavelength of maximum absorption and emission were red-shifted …

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Study Of The Protonation States Of The Curcumin Molecule And Their Visible Absorption Spectra In Aqueous Solution Using M06, Smd, And Tddft And Compared To Experiment, Joseph D. Alia, Peter Braegelmann, Timothy Roettgen, Hannah Goemann Apr 2015

Study Of The Protonation States Of The Curcumin Molecule And Their Visible Absorption Spectra In Aqueous Solution Using M06, Smd, And Tddft And Compared To Experiment, Joseph D. Alia, Peter Braegelmann, Timothy Roettgen, Hannah Goemann

Chemistry Publications

Curcumin, the primary natural dye from the spice turmeric, has been of recent interest due to its possible health benefits as an antioxidant and possible anti cancer and anti Alzheimer's properties. Limited solubility and instability in water are of primary importance when considering curcumin's possible uses as a pharmaceutical. DFT computations were carried out using B3LYP and MO6 density functionals and the SMD solvent model for water. TDDFT computations were carried out on geometries optimized in water as described by the SMD solvent model. It is found that M06 with the 3-21G* basis set and SMD solvent model gives accurate …

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Computational Study Of The Visible Spectrum Of Curcumin's Protonation States, Peter Braegelmann, Joseph D. Alia Apr 2015

Computational Study Of The Visible Spectrum Of Curcumin's Protonation States, Peter Braegelmann, Joseph D. Alia

Chemistry Publications

Curcumin, the main dye in the important Indian spice turmeric, has received much attention recently for its potential anti-cancer and anti-Alzheimer properties.1 Our study computes the thermodynamics and spectroscopic properties of curcumin’s various protonation states using several methods and compares the results to experiment. M06/3-21G* gave the best thermodynamic results, while M06 with 3-21G* and 6-31G* gave good spectroscopic results for the neutral and dianionic forms of curcumin. However, applying diffuse functions appears to be necessary for the trianionic form. Interestingly, M06 and B3LYP with 6-31+G* gave good spectroscopic results for the singly anionic form.

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Au Nanostructured Surfaces For Electrochemical And Localized Surface Plasmon Resonance-Based Monitoring Of Α-Synuclein-Small Molecule Interactions., Xin R Cheng, Gregory Q Wallace, François Lagugné-Labarthet, Kagan Kerman Feb 2015

Au Nanostructured Surfaces For Electrochemical And Localized Surface Plasmon Resonance-Based Monitoring Of Α-Synuclein-Small Molecule Interactions., Xin R Cheng, Gregory Q Wallace, François Lagugné-Labarthet, Kagan Kerman

Chemistry Publications

In this proof-of-concept study, the fabrication of novel Au nanostructured indium tin oxide (Au-ITO) surfaces is described for the development of a dual-detection platform with electrochemical and localized surface plasmon resonance (LSPR)-based biosensing capabilities. Nanosphere lithography (NSL) was applied to fabricate Au-ITO surfaces. Oligomers of α-synuclein (αS) were covalently immobilized to determine the electrochemical and LSPR characteristics of the protein. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were performed using the redox probe [Fe(CN)6](3-/4-) to detect the binding of Cu(II) ions and (-)-epigallocatechin-3-gallate (EGCG) to αS on the Au-ITO surface. Electrochemical and LSPR data were complemented by Thioflavin-T (ThT) …

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Genetic Encoding Of The Post-Translational Modification 2-Hydroxyisobutyryl-Lysine, William A. Knight, Thomas A. Cropp Jan 2015

Genetic Encoding Of The Post-Translational Modification 2-Hydroxyisobutyryl-Lysine, William A. Knight, Thomas A. Cropp

Chemistry Publications

We report the synthesis and genetic encoding of a recently discovered posttranslational modification, 2-hydroxyisobutryl-lysine, to the genetic code of E. coli. The production of homogeneous proteins containing this amino acid will facilitate the study of modification in full-length proteins.

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Electrolyte Pore/Solution Partitioning By Expanded Grand Canonical Ensemble Monte Carlo Simulation, F. Moucka, D. Bratko, A. Luzar Jan 2015

Electrolyte Pore/Solution Partitioning By Expanded Grand Canonical Ensemble Monte Carlo Simulation, F. Moucka, D. Bratko, A. Luzar

Chemistry Publications

Using a newly developed grand canonical Monte Carlo approach based on fractional exchanges of dissolved ions and water molecules, we studied equilibrium partitioning of both components between laterally extended apolar confinements and surrounding electrolyte solution. Accurate calculations of the Hamiltonian and tensorial pressure components at anisotropic conditions in the pore required the development of a novel algorithm for a self-consistent correction of nonelectrostatic cut-off effects. At pore widths above the kinetic threshold to capillary evaporation, the molality of the salt inside the confinement grows in parallel with that of the bulk phase, but presents a nonuniform width-dependence, being depleted at …

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Salt And Water Uptake In Nanocon!Nement Under Applied Electric Field: An Open Ensemble Monte Carlo Study, F. Moucka, D. Bratko, A. Luzar Jan 2015

Salt And Water Uptake In Nanocon!Nement Under Applied Electric Field: An Open Ensemble Monte Carlo Study, F. Moucka, D. Bratko, A. Luzar

Chemistry Publications

Permeation of electrolytes in nanoporous materials underlies many applications in energy and materials technologies. Wetting of apolar nanopores can be enhanced by electric !eld, attracting water and ions from unperturbed electrolyte bath. We study absorption of water and NaCl in the pores by Expanded Ensemble Grand Canonical Monte Carlo simulation, which implements particle insertions and deletions through incremental changes in particles’ coupling with the system. We determine the uptake of water and ions in the pores, and concomitant changes in pore thermodynamics, as functions of !eld strength in the pore and salinity in the external bath. Pressure increase and reduction …

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Dynamic Control Of Nanopore Wetting In Water And Saline Solutions Under An Electric Field, D. Vanzo, D. Bratko, A. Luzar Jan 2015

Dynamic Control Of Nanopore Wetting In Water And Saline Solutions Under An Electric Field, D. Vanzo, D. Bratko, A. Luzar

Chemistry Publications

Field-induced nanopore wetting by aqueous solutions, including electrolytes, provides opportunities for a variety of applications. Con!icting porosity requirements have so far precluded direct implementations of a two-way control: the pores have to be su"ciently wide to allow water in#ltration at experimentally relevant voltages but should not exceed the kinetic threshold for spontaneous expulsion in the absence of the #eld. Applicable widths are restricted below a few nanometers. Only a narrow window of #elds and pore geometries can simultaneously satisfy both of the above requirements. Accurate accounts of wetting equilibria and dynamics at nanoscale porosity require molecular level descriptions. Here we …

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Tunable 3d Plasmonic Cavity Nanosensors For Surface-Enhanced Raman Spectroscopy With Sub Femtomolar Limit Of Detection, Mohammadali Tabatabei, Mohamadreza Najiminaini, Kiefer Davieau, Bozena Kaminska, Mahi Singh, Jeff Carson, Francois Lagugne-Labarthet Jan 2015

Tunable 3d Plasmonic Cavity Nanosensors For Surface-Enhanced Raman Spectroscopy With Sub Femtomolar Limit Of Detection, Mohammadali Tabatabei, Mohamadreza Najiminaini, Kiefer Davieau, Bozena Kaminska, Mahi Singh, Jeff Carson, Francois Lagugne-Labarthet

Chemistry Publications

Metallic nanohole arrays (NHAs) with a high hole density have emerged with potential applications for surface-enhanced Raman spectroscopy (SERS) including the detection of analytes at ultra-low concentrations. However, these NHA structures generally yield weak localized surface plasmon resonance (LSPR) which is a prerequisite for SERS measurements. In this work, a compact three-dimensional (3D) tunable plasmonic cavity with extraordinary optical transmission properties serves as a molecular sensor with sub-femtomolar detection. The 3D nanosensor consists of a gold film containing a NHA with an underlying cavity and a gold nanocone array at the bottom of the cavity. These nanosensors provide remarkable surface …

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Resin-Supported Arylstannanes As Precursors For Radiolabeling With Iodine: Benzaldehydes, Benzoic Acids, Benzamides, And Nhs Esters, Mustafa Janabi, Catherine M. Pollock, Ann-Marie Chacko, Duncan H. Hunter Sep 2014

Resin-Supported Arylstannanes As Precursors For Radiolabeling With Iodine: Benzaldehydes, Benzoic Acids, Benzamides, And Nhs Esters, Mustafa Janabi, Catherine M. Pollock, Ann-Marie Chacko, Duncan H. Hunter

Chemistry Publications

A highly cross-linked polystyrene resin bearing a reactive chlorostannane moiety 1 has been used to generate a variety of arylstannane radiopharmaceutical precursors for no-carrier-added radioiodination. The resins were characterized for their solvent compatibility and sensitivity to acid cleavage. Resin-supported arylstannanes synthesized via their aryl lithium analogues include 3- and 4-stannylbenzaldehydes, 3- and 4-stannylbenzoic acids, and 3- and 4-N-succinimidyl benzoates. A three-step route to the resin-supported stannylbenzoic acids 12a/b was developed through resin-supported benzaldehydes 11a/b. The aldehyde to acid conversion efficiency is >90%, and acid loading capacities of 0.66–0.94 mmol/g were obtained. Resin-supported N-succinimidyl benzoates 16a/b …

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Synthesis Of (+)-Bovidic Acid, Geoffrey A. Phillips, Timothy B. Wright, Andrew C. Stevens, Brian Pagenkopf Aug 2014

Synthesis Of (+)-Bovidic Acid, Geoffrey A. Phillips, Timothy B. Wright, Andrew C. Stevens, Brian Pagenkopf

Chemistry Publications

(+)-Bovidic acid is an 18-carbon hydroxyfuranoid acid isolated from the pelage of the gaur (Bosfrontalis) and displays potential as an insect repellant. Both a formal and total synthesis of (+)-bovidic acid was carried out with the core of the natural product being synthesized through Mukaiyama aerobic oxidative cyclization employing the second-generation Co(nmp)2 catalyst.

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The [4+2] Cycloaddition Of Donor-Acceptor Cyclobutanes And Nitrosoarenes., Naresh Vemula, Andrew C Stevens, Tyler B Schon, Brian L Pagenkopf Feb 2014

The [4+2] Cycloaddition Of Donor-Acceptor Cyclobutanes And Nitrosoarenes., Naresh Vemula, Andrew C Stevens, Tyler B Schon, Brian L Pagenkopf

Chemistry Publications

The Yb(OTf)3 catalyzed [4+2] cycloaddition between donor-acceptor cyclobutanes and nitrosoarenes is disclosed. This method facilitates the synthesis of tetrahydro-1,2-oxazines in good to excellent yields as single diastereomers. Except for a few electron-deficient nitrosoarenes, excellent regioselectivity was observed throughout these studies.

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Enhanced Magnetic Anisotropy In Cobalt-Carbide Nanoparticles, Ahmed A. El-Gendy, Meichun Qian, Zachary J. Huba, Shiv N. Khanna, Everett E. Carpenter Jan 2014

Enhanced Magnetic Anisotropy In Cobalt-Carbide Nanoparticles, Ahmed A. El-Gendy, Meichun Qian, Zachary J. Huba, Shiv N. Khanna, Everett E. Carpenter

Chemistry Publications

An outstanding problem in nano-magnetism is to stabilize the magnetic order in nanoparticles at room temperatures. For ordinary ferromagnetic materials, reduction in size leads to a decrease in the magnetic anisotropy resulting in superparamagnetic relaxations at nanoscopic sizes. In this work, we demonstrate that using wet chemical synthesis, it is possible to stabilize cobalt carbide nanoparticles which have blocking temperatures exceeding 570 K even for particles with magnetic domains of 8 nm. First principles theoretical investigations show that the observed behavior is rooted in the giant magnetocrystalline anisotropies due to controlled mixing between C p- and Co d-states.

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Wetting Transparency Of Graphene In Water, J. Driskill, D. Vanzo, D. Bratko, A. Luzar Jan 2014

Wetting Transparency Of Graphene In Water, J. Driskill, D. Vanzo, D. Bratko, A. Luzar

Chemistry Publications

Measurements of contact angle on graphene sheets show a notable dependence on the nature of the underlying substrate, a phenomenon termed wetting transparency. Our molecular modeling studies reveal analogous transparency in case of submerged graphene fragments in water. A combined effect of attractive dispersion forces, angle correlations between aqueous dipoles, and repulsion due to the hydrogen-bond-induced orientation bias in polarized hydration layers acting across graphene sheet, enhances apparent adhesion of water to graphene. We show wetting free energy of a fully wetted graphene platelet to be about 8 mNm−1 lower than for graphene wetted only on one side, which gives …

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Astroecology, Cosmo-Ecology, And The Future Of Life, Michael Noah Mautner Jan 2014

Astroecology, Cosmo-Ecology, And The Future Of Life, Michael Noah Mautner

Chemistry Publications

Astroecology concerns the relations between life and space resources, and cosmo-ecology extrapolates these relations to cosmological scales. Experimental astroecology can quantify the amounts of life that can be derived from space resources. For this purpose, soluble carbon and electrolyte nutrients were measured in asteroid/meteorite materials. Microorganisms and plant cultures were observed to grow on these materials, whose fertilities are similar to productive agricultural soils. Based on measured nutrient contents, the 1022 kg carbonaceous asteroids can yield 1018 kg biomass with N and P as limiting nutrients (compared with the estimated 1015 kg biomass on Earth). These data …

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A Novel Two-Laser Interface For Coupling Capillary Electrochromatography With Ion-Trap Time-Of-Flight Mass Spectrometry, David C. Simpson, Alexander J. Yates, John H. Knox, Pat R.R. Langridge-Smith Jan 2014

A Novel Two-Laser Interface For Coupling Capillary Electrochromatography With Ion-Trap Time-Of-Flight Mass Spectrometry, David C. Simpson, Alexander J. Yates, John H. Knox, Pat R.R. Langridge-Smith

Chemistry Publications

An interface has been developed for the hyphenation of capillary electrochromatography (CEC) with mass spectrometry (MS). Chromatographic eluate vaporization and selective analyte ionization occur within a quadrupole ion-trap, which permits significant instrument simplification when compared with the atmospheric pressure interfaces typically used for CEC-MS. Vaporization is achieved using laser desorption at 1064 nm while ionization is accomplished through UV photoionization. This two-step approach, through ionization laser wavelength selection, can provide ultratrace analysis with high selectivity. The mass spectrometer is a hybrid ion-trap time-of-flight (TOF) instrument in which the ion-trap is used in radio frequency-only mode, with DC-pulse ejection, to provide …

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Direct Observation Of Metal Nanoparticles As Heterogeneous Nuclei For The Condensation Of Supersaturated Organic Vapors: Nucleation Of Size-Selected Aluminum Nanoparticles In Acetonitrile And N-Hexane Vapors, Victor Abdelsayed, M. Samy El-Shall Jan 2014

Direct Observation Of Metal Nanoparticles As Heterogeneous Nuclei For The Condensation Of Supersaturated Organic Vapors: Nucleation Of Size-Selected Aluminum Nanoparticles In Acetonitrile And N-Hexane Vapors, Victor Abdelsayed, M. Samy El-Shall

Chemistry Publications

This work reports the direct observation and separation of size-selected aluminum nanoparticlesacting as heterogeneous nuclei for the condensation of supersaturated vapors of both polar and nonpolar molecules. In the experiment, we study the condensation of supersaturated acetonitrile and n-hexane vapors on charged and neutral Al nanoparticles by activation of the metalnanoparticles to act as heterogeneous nuclei for the condensation of the organic vapor.Aluminum seed nanoparticles with diameters of 1 and 2 nm are capable of acting as heterogeneous nuclei for the condensation of supersaturated acetonitrile and hexane vapors. The comparison between the Kelvin and Fletcher diameters indicates that for theheterogeneous …

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Nanoconfined Water Under Electric Field At Constant Chemical Potential Undergoes Electrostriction, Davide Vanzo, D. Bratko, Alenka Luzar Jan 2014

Nanoconfined Water Under Electric Field At Constant Chemical Potential Undergoes Electrostriction, Davide Vanzo, D. Bratko, Alenka Luzar

Chemistry Publications

Electric control of nanopore permeation by water and solutions enables gating in membrane ion channels and can be exploited for transient surface tuning of rugged substrates, to regulate capillary permeability in nanofluidics, and to facilitate energy absorption in porous hydrophobic media. Studies of capillary effects, enhanced by miniaturization, present experimental challenges in the nanoscale regime thus making molecular simulations an important complement to direct measurement. In a molecular dynamics (MD) simulation, exchange ofwater between the pores and environment requires modeling of coexisting confined and bulk phases, with confined water under the field maintaining equilibrium with the unperturbed environment. In the …

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Proton-Bound Dimers Of Nitrogen Heterocyclic Molecules: Substituent Effects On The Structures And Binding Energies Of Homodimers Of Diazine, Triazine, And Fluoropyridine, Isaac K. Attah, Sean P. Platt, Michael Mautner, M. S. El-Shall, Saadullah G. Aziz, Abdulrahman O. Alyoubi Jan 2014

Proton-Bound Dimers Of Nitrogen Heterocyclic Molecules: Substituent Effects On The Structures And Binding Energies Of Homodimers Of Diazine, Triazine, And Fluoropyridine, Isaac K. Attah, Sean P. Platt, Michael Mautner, M. S. El-Shall, Saadullah G. Aziz, Abdulrahman O. Alyoubi

Chemistry Publications

The bonding energies of proton-bound homodimers BH+B were measured by ion mobilityequilibrium studies and calculated at the DFT B3LYP/6-311++G* * level, for a series of nitrogen heterocyclic molecules (B) with electron-withdrawing in-ring N and on-ring F substituents. The binding energies (ΔH°dissoc) of the proton-bound dimers (BH+B) vary significantly, from 29.7 to 18.1 kcal/mol, decreasing linearly with decreasing the proton affinity of the monomer (B). This trend differs significantly from the constant binding energies of most homodimers of other organic nitrogen and oxygen bases. The experimentally measured ΔH°dissoc for (1,3-diazine)2H+, i.e., (pyrimidine)2H+ and …

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Unconventional Hydrogen Bonding To Organic Ions In The Gas Phase: Stepwise Association Of Hydrogen Cyanide With The Pyridine And Pyrimidine Radical Cations And Protonated Pyridine, Ahmed M. Hamid, M. Samy El-Shall, Rifaat Hilal, Shaaban Elroby, Saadullah G. Aziz Jan 2014

Unconventional Hydrogen Bonding To Organic Ions In The Gas Phase: Stepwise Association Of Hydrogen Cyanide With The Pyridine And Pyrimidine Radical Cations And Protonated Pyridine, Ahmed M. Hamid, M. Samy El-Shall, Rifaat Hilal, Shaaban Elroby, Saadullah G. Aziz

Chemistry Publications

Equilibrium thermochemical measurements using the ion mobility drift cell technique have been utilized to investigate the binding energies and entropy changes for the stepwise association of HCN molecules with the pyridine and pyrimidine radical cations forming the C5H5N+· (HCN)nand C4H4N2 +· (HCN)n clusters, respectively, with n = 1–4. For comparison, the binding of 1–4 HCN molecules to the protonated pyridine C5H5NH+(HCN)n has also been investigated. The binding energies of HCN to the pyridine and pyrimidine radical cations are nearly equal (11.4 and 12.0 kcal/mol, respectively) but weaker than the HCN binding to the protonated pyridine (14.0 kcal/mol). …

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Gram Scale Synthesis Of The C(1)-C(9) Fragment Of Amphidinolide C, Nicholas A Morra, Brian L Pagenkopf Oct 2013

Gram Scale Synthesis Of The C(1)-C(9) Fragment Of Amphidinolide C, Nicholas A Morra, Brian L Pagenkopf

Chemistry Publications

An allylic cis-epoxide prepared by Sharpless asymmetric epoxidation was transformed in 9 steps and 41% overall yield to the cyclization precursor 4 via a key one carbon homologation. Cobalt catalyzed aerobic oxidative cyclization of 4 gave the trans-THF in 94% yield at gram scale. Subsequent manipulations, including a Still-Gennari olefination, Sharpless asymmetric dihydroxylation, Corey-Fuchs alkynylation and Kazmaier hydrostannylation provided the fully functionalized C(1)-C(9) fragment 2 suitable for cross coupling. The sequence is readily scalable and provides gram quantities of 2

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Optical Properties Of Silver And Gold Tetrahedral Nanopyramid Arrays Prepared By Nanosphere Lithography, M. Tabatabaei, A. Sangar, N. Kazemi-Zanjani, P. Torchio, A. Merlen, Francois Lagugne-Labarthet Jun 2013

Optical Properties Of Silver And Gold Tetrahedral Nanopyramid Arrays Prepared By Nanosphere Lithography, M. Tabatabaei, A. Sangar, N. Kazemi-Zanjani, P. Torchio, A. Merlen, Francois Lagugne-Labarthet

Chemistry Publications

Tetrahedral nanopyramids made of silver and gold over ITO/glass surfaces are fabricated. Our protocol is based on nanosphere lithography (NSL) with the deposition of thicker metal layers. After removing the microspheres used in the NSL process, an array of metallic tetrahedral nanostructures of ~350-400 nm height is formed. The reported procedure avoids the use of any stabilizing surfactant molecules that are generally necessary to segregate the individual particles onto surfaces. We focus here on the optical and the physical properties of these plasmonic surfaces using near-field spectroscopy in conjunction with finite difference time domain (FDTD) modeling of the electric field. …

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Hydration Of The Pyrimidine Radical Cation And Stepwise Solvation Of Protonated Pyrimidine With Water, Methanol, And Acetonitrile, Ahmed M. Hamid, Pramod Sharma, M. Samy El-Shall, Rifaat Hilal, Shaaban Elroby, Saadullah G. Aziz, Abdulrahman O. Alyoubi Jan 2013

Hydration Of The Pyrimidine Radical Cation And Stepwise Solvation Of Protonated Pyrimidine With Water, Methanol, And Acetonitrile, Ahmed M. Hamid, Pramod Sharma, M. Samy El-Shall, Rifaat Hilal, Shaaban Elroby, Saadullah G. Aziz, Abdulrahman O. Alyoubi

Chemistry Publications

Equilibrium thermochemical measurements using an ion mobility drift cell technique have been utilized to investigate the binding energies and entropy changes associated with the stepwise hydration of the biologically significant ions pyrimidine radical cation and protonated pyrimidine. The binding energy of the hydrated pyrimidine radical cation is weaker than that of the proton-bound dimer pyrimidineH+(H2O) consistent with the formation of a weak carbon-based CHδ+··OH2 hydrogen bond (11.9 kcal/mol) and a stronger NH+··OH2 hydrogen bond (15.6 kcal/mol), respectively. Other proton-bound dimers such as pyrimidineH+(CH3OH) and pyrimidineH+(CH3CN) exhibit higher binding energies (18.2 kcal/mol and 22.8 kcal/mol, respectively) due to the higher proton …

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Dynamics At A Janus Interface, M. Von Domaros, D. Bratko, B. Kirchner, A. Luzar Jan 2013

Dynamics At A Janus Interface, M. Von Domaros, D. Bratko, B. Kirchner, A. Luzar

Chemistry Publications

Electric field effects on water interfacial properties abound, ranging from electrochemical cells to nanofluidic devices to membrane ion channels. On the nanoscale, spontaneous orientational polarization of water couples with field alignment, resulting in an asymmetric wetting behavior of opposing surfacesa field-induced analogue of a chemically generated Janus interface. Using atomistic simulations, we uncover a new and significant field polarity (sign) dependence of the dipolar- orientation polarization dynamics in the hydration layer. Applying electric fields across a nanoparticle, or a nanopore, can lead to close to 2 orders of magnitude difference in response times of water polarization at opposite surfaces. Typical …

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Bf2obn∙Oet2: A Novel Lewis Acid And Its Use In A Regio- And Stereo-Selective Opening Of Trisubstituted Epoxides And Its Application Towards Amphidinolide C, Nicholas A. Morra, Brian Pagenkopf Dec 2012

Bf2obn∙Oet2: A Novel Lewis Acid And Its Use In A Regio- And Stereo-Selective Opening Of Trisubstituted Epoxides And Its Application Towards Amphidinolide C, Nicholas A. Morra, Brian Pagenkopf

Chemistry Publications

The generation of a new Lewis acid (BF2OBn·OEt2) has been reported, and its usefulness has been demonstrated in the regio- and stereoselective ring-opening of trisubstituted epoxides. This Lewis acid is one in a series of new Lewis acids generated from BF3·OEt2 that display varying levels of Lewis acidity. When paired with a modified Shi epoxidation protocol, highly functionalized propionate units, such as those found in a wide variety of natural products, can be accessed. In conjunction with a Mukaiyama oxidative cyclization employing our second generation catalyst Co(nmp)2, this procedure ultimately culminated in the shortest and highest yielding route towards the …

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Magnetic Properties Of Co2c And Co3c Nanoparticles And Their Assemblies, Kyler J. Carroll, Zachary J. Huba, Steven R. Spurgeon, Meichun Qian, Shiv N. Khanna, Daniel M. Hudgins, Mitra L. Taheri, Everett E. Carpenter Jan 2012

Magnetic Properties Of Co2c And Co3c Nanoparticles And Their Assemblies, Kyler J. Carroll, Zachary J. Huba, Steven R. Spurgeon, Meichun Qian, Shiv N. Khanna, Daniel M. Hudgins, Mitra L. Taheri, Everett E. Carpenter

Chemistry Publications

Nano-composite material consisting of Co2C and Co3C nanoparticles has recently been shown to exhibit unusually large coercivities and energy products. Experimental studies that can delineate the properties of individual phases have been undertaken and provide information on how the coercivities and the energy product change with the size and composition of the nanoparticles. The studies indicate that while both phases are magnetic, the Co3C has higher magnetization and coercivity compared to Co2C. Through first principles electronic structure studies using a GGA+U functional, we provide insight on the role of C intercalation on …

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Controlled Synthesis Of Superparamagnetic Iron-Oxide Nanoparticles By Phase Transformation, Mark A. Laurenzi, Everett E. Carpenter Jan 2012

Controlled Synthesis Of Superparamagnetic Iron-Oxide Nanoparticles By Phase Transformation, Mark A. Laurenzi, Everett E. Carpenter

Chemistry Publications

A synthesis procedure for generating a uniform distribution of iron-oxide nanoparticles from an amorphous precursor is reported. The investigation suggests no evidence of the formation of unwanted surface oxide layers, internal stress, and multiple phases. This is likely because the physical properties of the diffusion fields surrounding the nanoparticles are self-limiting by Fe(II) depletion. Inside the diffusion field surrounding the nucleation site, decreasing Fe(II) concentration results in a decrease in the diffusion rate that continues to decrease until self-limiting kinetic arrest occurs. The initial Fe(II) concentration is established by reducing a system abundant in Fe(III) by means of exposure to …

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Wettability Of Pristine And Alkyl-Functionalized Graphane, Davide Vanzo, Dusan Bratko, Alenka Luzar Jan 2012

Wettability Of Pristine And Alkyl-Functionalized Graphane, Davide Vanzo, Dusan Bratko, Alenka Luzar

Chemistry Publications

Graphane is a hydrogenated form of graphene with high bandgap and planar structure insensitive to a broad range of chemical substitutions. We describe an atomistic simulation approach to predict wetting properties of this new material. We determine the contact angle to be 73°. The lower hydrophobicity compared to graphene is explained by the increased planar density of carbon atoms while we demonstrate that the presence of partial charges on carbonand hydrogen atoms plays only a minor role. We further examine the effects of graphane functionalization by alkyl groups of increasing chain lengths. The gradual increase in contact angle with chain …

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