Chemistry Commons^™

Toward The Design Of Mr Agents For Imaging Β-Cell Function, Mark Woods, Shanrong Zhang, A. Dean Sherry

Chemistry Faculty Publications and Presentations

The chemistry of Gd3+-based MRI agents has advanced considerably during the past decade toward agents with higher relaxivity and agents that respond to physiology and / or metabolism. This review describes various approaches that have been taken toward the development of responsive contrast agents and discusses the importance of fast water exchange for advancement of targeted Gd3+-based agents with higher sensitivity. The recent discovery of Eu3+ complexes having extraordinarily slow water exchange has opened a new avenue in contrast agent design based upon the chemical exchange saturation transfer (CEST) mechanism. These new paramagnetic complexes called PARACEST agents offer new possibilities …

Synthesis, Relaxometric And Photophysical Properties Of A New Ph-Responsive Mri Contrast Agent: The Effect Of Other Ligating Groups On Dissociation Of A P-Nitrophenolic Pendant Arm, Mark Woods, Garry Kiefer, Simon G. Bott, Aminta Castillo-Muzquiz, Carrie Eshelbrenner, Lydie Michaudet, Kenneth Mcmillan, Siva D.K. Mudigunda, Doug Ogrin, Gyula Tircso, Shanrong Zhang, Piyu Zhao, A. Dean Sherry

Chemistry Faculty Publications and Presentations

Two gadolinium(III) chelates, GdNP-DO3A (1-methlyene-(p-NitroPhenol)-1,4,7,10-tetraazacycloDOdecane-4,7,10-triAcetate) and GdNP-DO3AM (1-methlyene(p-NitroPhenol)-1,4,7,10-tetraazacycloDOdecane-4,7,10-triacetAMide), containing a single nitrophenolic pendant arm plus either three acetate or three amide pendant arms were synthesized and characterized. The properties of the gadolinium, terbium, and dysprosium complexes of these ligands were examined as a function of pH. The extent and mechanism of the changes in water relaxivity with pH of each gadolinium complex was found to differ substantially for the two complexes. The water relaxivity of Gd(NP-DO3A) increases from 4.1 …

Pressure-Induced Insulating State In An Organic Superconductor, Gary L. Gard, Javid Mohtasham, J. A. Schlueter, C. Pfleiderer, J. Wosnitza, J. Hagel

Chemistry Faculty Publications and Presentations

The electronic-transport properties of the quasi-two-dimensional organic superconductor β″–(BEDT-TTF)₂SF₅CH₂CF₂SO₃, where BEDT-TTF stands for bisethylenedithio-tetrathiafulvalene, have been investigated in magnetic fields up to 15 T and under hydrostatic pressure up to about 14 kbars. Shubnikov–de Haas data reveal a nonmonotonic pressure dependence of the holelike Fermi surface, a roughly linear increase of the electron g factor, and an approximately linear decrease of the cyclotron effective mass. By assuming that the latter reflects the pressure-induced reduction of the superconducting coupling parameter λ the rapid reduction of the superconducting transition temperature Tc(p) can be reasonably well described by the modified McMillan equation. Above …

Enhanced Magnetic Quantum Oscillations In The Mixed State Of A Two-Dimensional Organic Superconductor, J. Wosnitza, J. Hagel, P. J. Meeson, D. Bintley, J. A. Schlueter, Javid Mohtasham, Rolf Walter Winter, Gary L. Gard

Chemistry Faculty Publications and Presentations

We report on de Haas–van Alphen (dHvA) oscillations observed in the mixed state of the organic superconductor β″–(BEDT-TTF)₂SF₅CH₂CF₂SO₃ (BEDT-TTF stands for bisethylenedithio-tetrathiafulvalene) utilizing the field-modulation technique and torque magnetometry. At low temperatures (30 mK), the dHvA signal persists down to 1.4 T well below the upper critical field Bc2≈3.6T. Contrary to most theoretical predictions and previous experimental findings, no additional damping of the dHvA-oscillation amplitude, but a reduced damping of the dHvA signal is found. This highly unusual effect might indicate a reduced quasiparticle scattering rate or an additional oscillatory contribution in the superconducting state.

Solving Chemical Problems Of Environmental Importance Using Cavity Ring-Down Spectroscopy, Dean B. Atkinson

Chemistry Faculty Publications and Presentations

Cavity ring-down (CRD) is a sensitive variant of traditional absorption spectroscopy that has found increasing use in a number of chemical measurement applications. This review focuses on applications of cavity ring-down spectroscopy that will be of interest to environmental chemists and analytical chemists working on environmental problems. The applications are classified into direct monitoring approaches, indirect analysis methods and ancillary studies and a differentiation is made between field-tested instruments and proof of principle studies.

Space-Group Revision For 4-Formylphenylboronic Acid, Frank R. Fronczek, Nadia N. St Luce, Robert M. Strongin

Chemistry Faculty Publications and Presentations

The space group of the title compound, C₇H₇BO₃, previously reported to be P, is properly Cc. There is no disorder of the formyl group or in the H atoms of the B(OH)₂ group. Molecules lie on approximate twofold axes and are related by approximate centers, which relate all but the formyl O atom and boronic acid H atoms. The B-O distances are 1.363 (2) and 1.370 (2) Å.

Trimethylsulfonium Methanesulfonate, Frank R. Fronczek, Rolanda J. Johnson, Robert M. Strongin

Chemistry Faculty Publications and Presentations

In the title compound, C₃H₉S⁺.CH₃O₃S^-, a thermal decomposition product of dimethyl sulfoxide, both cation and anion lie on mirror planes. In the cation, the S atom lies 0.792 (2) Å out of the plane defined by the three C atoms, with S-C distances of 1.781 (2) and 1.786 (3) Å. In the anion, the S-O distances are 1.4556 (14) and 1.4646 (19) Å, and the S-C distance is 1.759 (3) Å.

Structure And Phase Transitions Of The 6, 6-Cyclopropane Isomer Of C_ {61} H_ {2}, M. R. Stetzer, Paul A. Heiney, Peter W. Stephens, R. E. Dinnebier, Q. Zhu, Andrew R. Mcghie, Robert M. Strongin, B. M. Brandt, Amos B. Smith Iii

Chemistry Faculty Publications and Presentations

We have used x-ray powder diffraction and differential scanning calorimetry to study the crystalline structures and thermal behavior of the 6,6-cyclopropane isomer of C₆₁H₂. At room temperature, the C₆₁H₂ cyclopropane molecules, like those of the 6,5-annulene isomer and C₆₀O epoxide, are orientationally disordered and crystallize on a face-centered-cubic lattice such that their methylene groups are statistically disordered among the octahedral voids. Unlike 6,5−C₆₁H₂ and C₆₀O, the low-temperature structure is not Pa3¯, but rather a low-symmetry orthorhombic lattice in which a≈b

Sol-Gel Ph Sensors And Sol-Gel Metal-Removing Sorbents, Dong Liu

Dissertations and Theses

Sol-gel silica is a porous glasslike material that can be prepared at room temperature. In this work, sol-gel method was employed to develop sol-gel sensors for pH measurement and sol-gel silica sorbents for removal of heavy metals.

Sol-gel pH sensors were prepared by entrapping pH indicators in porous solgel silica films. The feasibility of developing optical pH sensors with linear response over a wide pH range by using mixtures of multiple indicators was demonstrated. Theoretical criteria and experimental procedures for selecting indicators and determining optimum ratios of indicators were discussed. A linear response over 4.5 pH units was obtained for …

The Synthesis And Characterization Of A Porphyrin Oligomer As A Potential Antenna For Light Harvesting Solar Cells, Tristan Timothy Jenkins

Dissertations and Theses

Mankind's attempts to harvest the sun have resulted in photocells with about 15% overall energy conversion efficiency. The best of these cells consist of a light-sensitive dye attached to a semiconductor. Absorbed light energy is transferred to the semiconductor via the delivery of an excited electron from the dye. Dye electrons are replenished with a redox solution, coupling the dye to the counter electrode.

This research was the beginning of an exploration into some potential improvements in the cell. First of all, the redox solution is a corrosive liquid, and leaks present a problem. A porphyrin oligomer with a TCPP …

Xanthones As Antimalarial Agents: Binding Interactions Between Heme Analogues And Xanthones, Jane Xu Kelly

Dissertations and Theses

Human falciparum malaria is caused by Plasmodium falciparum parasite, which digests host hemoglobin within its food vacuole, releasing toxic heme. P. falciparum detoxifies free heme to hemozoin by polymerization. This process is believed to be the target of most successful antimalarial drugs, chloroquine and quinine, which are now losing their effectiveness due to the spread of multi-drug resistant strains. Xanthones were recognized in the laboratory of Dr. M. Riscoe (Portland VA Medical Center) to bind to heme, preventing heme polymerization.

This thesis reports a study of the interactions of a potential antimalarial agent, 4,5-dihydroxyxanthone (X2), with heme and tin (IV) …

Paramagnetic Nuclear Magnetic Resonance (Nmr) Studies On The Calcium Binding Site Of [Alpha]-Lactalbumin, Thomas Kurt Ritter

Dissertations and Theses

Paramagnetic NMR has drawn interest as a technique for extending the range of systems that can be investigated. The purpose of this study was to determine whether a combination of paramagnetic two-dimensional and relaxation techniques allows for assigning resonances corresponding to residues forming the metal binding site of proteins in which the metal is coordinated exclusively by amino acid side chains and which have been previously inaccessible to assignment.

α-Lactalbumin (LA) is a calcium binding protein with relatively broad NMR signals; this broadness has prevented complete assignment. LA has been the subject of many studies, because it can form a …

Syntheses And Characterizations Of Unsymmetrical Porphyrins As Photosensitizers For A Solid-State Solar Cell, Yinping Zhao

Dissertations and Theses

Solar light is the most important source of regenerative energy and represents mankind's only inexhaustible energy source. One of today's most promising tools to make use of solar energy is its direct conversion into electrical energy in a photovoltaic cell. The practical use of these solar cells depends on the price of the devices and therefore of the obtained energy. The conventional silicon cells, although efficient, are expensive for common consumer applications. The Grätzel cell is a photovoltaic system for harvesting the sun's energy that operates at about 10-15% overall efficiency, like a conventional solar cell, but does it at …

Efficient Implementation Of Image Compression-Postprocessing Algorithm Using A Digital Signal Processor, Nadir Sinaceur

Dissertations and Theses

In this thesis, an attempt has been made to develop a fast way to implement a post-processing algorithm for image compression. All the previous tests for this postprocessing algorithm, which we will present, have been only software based and did not consider the time parameter.

For this purpose a new algorithm is used to compute the 2-D DCT transform. This change made the process a lot faster on a Spare 5 workstation. We have then decided to further increase the speed of the post-processing scheme by implementing it on the ADSP21020 chip.

The results show that such a chip can …

Synthesis And Characterization Of Novel Sf5 Containing Fluoroalkyl Iodides And Derivatives, Julia Anne Renn

Dissertations and Theses

Preparation of four SF5-containing fluoroalkyl iodides and derivatives thereof was accomplished beginning with a simplified synthesis of ICF2CF2I. Characterization of the products followed using a variety of spectroscopic and physical methods. The simplified method for preparing ICF2CF2I from iodine and tetrafluoroethylene (TFE) involved a reaction temperature of approximately 54°C and pressures of less than two atmospheres for the TFE. The synthesized ICF2CF2I was reacted with S2F1o and tetrafluoroethylene to give SF5CF2CF2I. The subsequent synthesis of the SFs containing fluoroalkyl iodides and derivatives were carried out using SFsCF2CF2I as the starting material in a Carius tube reaction vessel. The synthesized SFs …

Structure, Dynamics, And Phase Transitions In The Fullerene Derivatives C_{60}O And C_{61}H_{2}, C. Meingast, G. Roth, L. Pintschovius, R. H. Michel, C. Stoermer, M. M. Kappes, Paul A. Heiney, Laurent Brard, Robert M. Strongin, Amos B. Smith Iii

Chemistry Faculty Publications and Presentations

The effect of perturbing the icosohedral symmetry of C₆₀ by the addition of the side groups -O and -CH₂ upon orientational order-disorder and glass transitions in solid C₆₀ has been studied by a combination of high-resolution capacitance dilatometry and single-crystal x-ray and powder inelastic neutron scattering. Both fullerene derivatives C₆₀O (epoxide) and C₆₁H₂ (6,5-annulene) are shown to undergo a sequence of transitions similar to that found in pure C₆₀, i.e., a first-order orientational ordering transition just below room temperature followed by an orientational glass transition at lower temperatures. Although the …

Fluorinated Polymer Films: Synthesis And Characterization, Anja Ulrike Schnurer

Dissertations and Theses

Three polyfluoroalkyl epoxides, (I OCH₂CHCH₂OCF₂CF₂SO₂F, II OCH₂CHCH₂(CF₂)₈F and III OCH₂CHCH₂O(CF₂)CF(CF₃)SO₂F) were photopolymerized with a cycloaliphatic diepoxide (Cyracure UVR-6110) to form highly crosslinked glassy films. Depth-dependent surface analysis with XPS show that these films are highly enriched with sulfonyl fluoride groups in the outer molecular surface. Film compositions of 17 % wt and more of the fluorinated I and III show surface characteristics of a film composed of 100 % wt of the …

Nmr Study Of Neurophysin Dimer Dissociation By Cosolvents, Jian Yao

Dissertations and Theses

Neurophysins (NPs) make up a relatively small, stable, and highly soluble class of proteins. They have physiological roles of storage and stabilizing' of peptide hormones oxytocin and vasopression within the posterior pituitary neurosecretory granules. At the concentration of NP found within the granules, NP would exist as a dimer in the absence or presence of bound peptide. The NP monomer-monomer interface involves B-sheet/ B-sheet contact, which can be modulated by the presence of cosolvent. This remarkable feature of NP makes it a model for Alzheimer's disease. One of the characteristics of Alzheimer's disease is the presence of plaques of B-amyloid …

Heme Proton Resonance Assignments And Kinetics Study In High-Spin And Mixed-Spin Metmyoglobin Complexes By Chemical Exchange Nmr Spectroscopy, Ying Luo

Dissertations and Theses

NMR studies of paramagnetic hemoproteins have improved significantly our understanding of the structure-function relationship of hemoproteins in general. Up to date most of the studies focus on low-spin ferric systems which are characterized by relatively narrow resonance peaks and concomitant better resolution.

However, characterizing in detail the NMR spectra of high-spin ferric hemoproteins is important since there are several hemoproteins, such as peroxidases, catalases, oxygenases, and some ferricytochromes that contain high-spin iron (III) in their biologically active forms. Yet assigning resonances from heme peripheral protons and/or heme pocket residues in high-spin myoglobins is a daunting undertaking. Only a sparse number …

Synthesis And Characterization Of Novel Fluorine Containing Alkylsulfonyls And Sulfonates : Fluorinated Sulfonyl Methanes And Derivatives, Nelson R. Holcomb

Dissertations and Theses

A series of salts of the strong fluorocarbon acid bis(trifluoromethylsulfonyl)methane were made: (CF3S02 ) 2CHK, (CF3S02 ) 2CHLi, [ (CF3S02 ) 2CH] 2Ca, [ (CF3S02 ) 2CH] 2Hg, (CF3S02 ) 2CHAg, [ (CF3S02 ) 2CH] 3La. Their reactivity and use as organic intermediates were investigated. The salts were made from their corresponding carbonates, oxides, or hydrides. The reaction times for the salts is generally short, however the purification process was laborious, involving recrystallization from organic solvents and drying under vacuum. The lithium salt is being evaluated as a solid state battery electrolyte. Derivatives of bis(trifluoromethylsulfonyl)methane were made by using the …

Synthesis And Characterization Of A Porphyrin Dyad, Dale A. Braden

Dissertations and Theses

The sun is a bountiful source of energy for our planet. .With the advent of photovoltaic cells, man has begun harnessing the sun's radiant energy, turning it into a form more directly useful: electricity. Commercially available solar cells currently operate at about 13% efficiency, sufficiently high to make them a viable source of electrical energy. It is of great interest, however, to improve their conversion efficiency, and to lower the cost of production so as to make them more economical, and thereby reduce our dependence upon traditional "dirty" sources of energy such as coal and oil. It has been found …

Studies In Fluorine Chemistry: 13c Nmr Investigation Of Sf5/So2f Fluorinated Systems, Yoon S. Choi

Dissertations and Theses

The purpose of this thesis was two fold: (i) The synthesis and characterization of SF5 containing dienes. (ii) The characterization of hydro/fluorocarbon compounds containing SF5/S02F groups via their 13C NMR spectra. A new SF5CH2CHBrCH2CF=CF2 was prepared and characterized as a precursor to new dielectric polymers. This new adduct was made from the reaction of pentafluorothio bromide with l,l,2-trifluoro-1,4-pentadiene. A SF5-diene was prepared from the reaction of pentafluorothio chloride with acetylene. This reaction involves a radical addition mechanism. The SF5 group is bonded to the carbon atom carrying the most hydrogens. SF5 - dienes are capable of undergoing different reactions, such …

Smectic-A —Smectic-C* —Smectic-C Multicritical Point In Ferroelectric Liquid Crystals, Shankar B. Rananavare, V. G. K. M. Pisipati, E. W. Wong

Chemistry Faculty Publications and Presentations

We report a smectic-A–smectic-C–smectic-C* (ACC*) multicritical point in mixtures of chiral DOBAMBC [p-(n-decyloxybenzylidene)-p-amino-(2-methyl-butyl)] cinnamate and achiral 10O.8 (4-decyloxybenzylidene-4-octylaniline). Studies of the phase diagram, tilt angle (θ), polarization (P), and helix pitch (p) indicate an ACC* Lifshitz point that can be described in terms of the extended Landau theory. Specifically, the T*_AC and the maximum polarization (P_m) exhibit quadratic composition dependence while the helical pitch length (p=2π/q) varies linearly. Both q and P_m vanish discontinuously at the C-C* …

Structure And Phase Transition Of The 6,5-Annulene Isomer Of C_{61}H_{2}, Andrea N. Lommen, Paul A. Heiney, Gavin B. M. Vaughan, Peter W. Stephens, Dengfa Liu, Dayin Li, Allan L. Smith, Andrew R. Mcghie, Robert M. Strongin, Laurent Brard, Amos B. Smith Iii

Chemistry Faculty Publications and Presentations

We have used differential scanning calorimetry and x-ray diffraction to study the crystalline phases of the 6,5-annulene isomer of C₆₁H₂. At 308 K the methylenated fullerenes are orientationally disordered in a face-centered cubic lattice with lattice parameter 14.19±0.02 Å. Below Tc=290 K the symmetry is lowered to Pa3¯, a simple-cubic structure. At 20 K the lattice parameter is 14.06±0.02 Å, with substantial statistical disorder remaining. The transition temperature in C₆₁H₂ is slightly higher than in C₆₀O and higher still than in C₆₀, but the three compounds exhibit orientationally …

Synthesis And Characterization Of Some Flourine-Containing Lithium Alkyl Sulfonates: Flourinated Sulfonates And Sf5-Containing Sulfonates, Steven A. Ullrich

Dissertations and Theses

Lithium salts of pentafluorothio alkyl sulfonic acids and perfluoroalkyl disulfonic acids were prepared for testing for possible use as polymer electrolytes. Most of these lithium salts were made from the corresponding sodium, potassium or calcium salts. Aqueous solutions of these salts were passed through polystyrene sulfonate ion exchange resin in the acid form to obtain aqueous solutions of the corresponding acids. The acids were then neutralized with lithium hydroxide using a pH meter. One salt was made by reacting the barium salt of the corresponding acid with lithium sulfate. A sulfonyl fluoride polymer (-0-CH2-C (CH20CF2CF2S02F) H-) n was reacted with …

Solubility Studies Of Iron(Iii) Oxides And Hydroxides, Victor L. Menting

Dissertations and Theses

The hydrolysis of iron(III) ions in aqueous solution forms a series of soluble hydroxide complexes with associated equilibrium constants. The solubility of iron(III) is controlled by the various soluble hydroxide complexes, and can, in theory, be calculated from the pH and equilibrium constants. Experimental verification of the calculated solubility has proven difficult due to the lack of sensitive analytical techniques and the presence of colloidal ferric hydroxide interferences. Recently, electrochemical methods for the determination of low levels of iron(III) have been developed using adsorptive cathodic stripping voltammetry which relies on the interfacial accumulation of the chelate of iron with Solochrome …

Neutron-Scattering Study Of Librations And Intramolecular Phonons In Rb_{2.6}K_{0.4}C_{60}, D. Reznik, W. A. Kamitakahara, D. A. Neumann, J. R. D. Copley, J. E. Fischer, Robert M. Strongin, M. A. Cichy, Amos B. Smith Iii

Chemistry Faculty Publications and Presentations

We report the results of inelastic neutron-scattering measurements on Rb_2.6K_0.4C₆₀. Librational modes were observed as broad peaks with maxima between 4.1 and 4.7 meV, as the temperature is lowered from 300 to 12 K. As in K₃C₆₀, no change in the width or position of the librational peak was observed when the sample was cooled through the superconducting transition. Thus any coupling of the librations to electronic states is small. The magnitude of the orientational potential barrier was estimated from the librational peak frequency. A flat background observed in the …

Atmospheric Hydrocarbon Analysis, Dawei Han

Dissertations and Theses

This treatise studied two correlated important issues in atmospheric chemistry: real-time monitoring of ambient air and removal mechanisms of atmospheric hydrocarbons. An analytical system was designed for the purpose of identification and measurement of sub-ppb level hydrocarbons of different reactivities in air samples. This analytical system was then applied to a series of smog-chamber studies which simulated the removal of reactive hydrocarbons from the atmosphere by reaction with hydroxyl radicals. Six representative atmospheric hydrocarbons (hexane, octane, toluene, m-xylene, a-xylene and mesitylene) were selected for these experiments. The experimental data indicated that the decay of atmospheric hydrocarbons under laboratory conditions is …

Orientational Phase Transition In Na_{X}C_{60} (1, T. Yildirim, J. E. Fischer, A. B. Harris, Peter W. Stephens, Dengfa Liu, Laurent Brard, Robert M. Strongin, Amos B. Smith Iii

Chemistry Faculty Publications and Presentations

X-ray diffraction and calorimetry data on cubic Na_xC₆₀(1<x60, e.g., T_m(x=1.3)=325 K. The ordered phases are the same as in pure C₆₀: simple cubic, space group Pa3¯, but the orientations in the disordered phase are more restricted. We explain how Na stabilizes the ordered phase to rather high T, while K and Rb do not, in terms of Coulomb interactions between C₆₀ molecules and and Na ions which we calculate from the local charge density of C₆₀.

Existence Of High-Order Superlattices In Orientationally Ordered C_{60}, J. E. Fischer, D. E. Luzzi, K. Kniaź, A. R. Mcghie, D. A. Ricketts-Foot, W. R. Romanow, Gavin B. M. Vaughan, Dayin Li, Allan L. Smith, Robert M. Strongin, M. A. Cichy, Laurent Bard, Amos B. Smith Iii

Chemistry Faculty Publications and Presentations

We correlate the presence or absence of high-order modulated structures in solid C₆₀ with the differential scanning calorimetry signature of the orientational ordering transition and other diagnostic data. We have searched for, but not observed, the 2a face-centered cubic structure recently observed in low-temperature electron and single-crystal x-ray diffraction. We conclude that the intrinsic ground state is the previously reported simple cubic structure [space groupPa3¯, a(14 K)=14.06 Å], and that other structures may be stabilized by defects or impurities.