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Synthesis and Electron Transfer Studies of Supramolecular Triads

Description: This study expands the role of polythiophenes as an electron donating chromophore within energy harvesting milti-modular donor-acceptor systems. The polythiophene moiety would act as an electron donating spacer group between the donor and acceptor entities, viz., phenothiazine and fulleropyrrolidine, respectively, in the newly synthesized supramolecular triads. The triads 10-{[2,2';5',2"] terthiophene-5-fulleropyrrolidine} phenothiazine and 10-{[2,2'] bithiophene-5-fulleropyrrolidine} phenothiazine were synthesized and characterized through electrochemical and spectroscopic methods to ascertain their structural integrity. the componets of the triads were selected for their established redox parameters. Phenothiazine would act as a secondary donor and would facilitate hole-transfer from the polythiophene primary electron donor, due to its ease of oxidation and yield a long-lived charge separated state. Fulleropyrrolidine would act as an acceptor for ease of reductive capabilities and its ability to hold multiple charges. Finally, occurrence of photoinduced electron transferleading to the anticipated charge separated states is established from advanced transient spectroscopic techniques on these novel supramolecular systems.
Date: May 2016
Creator: Bodenstedt, Kurt
Partner: UNT Libraries

Investigation of Electron Transfer-Based Photonic and Electro-Optic Materials and Devices

Description: Montana’s state program began its sixth year in 2006. The project’s research cluster focused on physical, chemical, and biological materials that exhibit unique electron-transfer properties. Our investigators have filed several patents and have also have established five spin-off businesses (3 MSU, 2 UM) and a research center (MT Tech). In addition, this project involved faculty and students at three campuses (MSU, UM, MT Tech) and has a number of under-represented students, including 10 women and 5 Native Americans. In 2006, there was an added emphasis on exporting seminars and speakers via the Internet from UM to Chief Dull Knife Community College, as well as work with the MT Department of Commerce to better educate our faculty regarding establishing small businesses, licensing and patent issues, and SBIR program opportunities.
Date: March 28, 2008
Creator: Bromenshenk, Jerry J; Abbott, Edwin H; Dickensheets, David; Donovan, Richard P; Hobbs, J D; Spangler, Lee et al.
Partner: UNT Libraries Government Documents Department

Nanowires, Capacitors, and Other Novel Outer-Surface Components Involved in Electron Transfer to Fe(III) Oxides in Geobacter Species

Description: The overall goal of this project was to better understand the mechanisms by which Geobacter species transfer electrons outside the cell onto Fe(III) oxides. The rationale for this study was that Geobacter species are often the predominant microorganisms involved in in situ uranium bioremediation and the growth and activity of the Geobacter species during bioremediation is primarily supported by electron transfer to Fe(III) oxides. These studies greatly expanded the understanding of electron transfer to Fe(III). Novel concepts developed included the potential role of microbial nanowires for long range electron transfer in Geobacter species and the importance of extracytoplasmic cytochromes functioning as capacitors to permit continued electron transfer during the hunt for Fe(III) oxide. Furthermore, these studies provided target sequences that were then used in other studies to tract the activity of Geobacter species in the subsurface through monitoring the abundance of gene transcripts of the target genes. A brief summary of the major accomplishments of the project is provided.
Date: December 22, 2008
Creator: Lovley, Derek, R.
Partner: UNT Libraries Government Documents Department

Final Report for Department of Energy grant DE-FG02-91ER45455, "Theoretical Study of Reactions at the Electrode-Electrolyte Interface"

Description: In this project, reaction rates were predicted by numerical methods, in a collaboration with Argonne National Laboratory . Emphasis is on electron transfer and transport involving ions known to be important in enhancing stress corrosion cracking in light water reactors and on electron transfer at oxide surfaces. In the latter part of the grant period we placed increased emphasis on development and use of self consistent tight binding methods for this kind of study. We showed that by careful fitting of results from first principles plane wave calculations,we could model surfaces and interfaces oxides and metals using these methods. We obtained results for the titanium/titanium oxide interface in this way and completed a model of the ruthenium dioxide surface using our innovative self consistent tight binding molecular dynamics methods. We completed development of a description of liquid water within the self consistent tight binding context and studied the rutile water 110 interface to determine if it is hydroxylated. A self consistent tight binding study of titanium metal surfaces demonstrated the usefulness of this method for metals. In collaboration with the Argonne group, we extended the tight binding calculations on rutile titania to the anatase form and made the first calculations of the relative stability of anatase and rutile as a function of crystallite size. We completed studies of small anatase particles in water using the method and found significant distortions of nanoparticle crystallite shapes as a consequence of interactions with the water.
Date: May 19, 2009
Creator: Halley, J. W.
Partner: UNT Libraries Government Documents Department

Synthesis and characterization of molecules for electron transfer research.

Description: Dimethoxynaphthalene (donor) and quinone (acceptor) have been chosen as a suitable redox pair and are bonded to either permethylated silane chains or corresponding permethylated alkyl chains to form Acceptor-(Bridge)-Donor molecules. The idea that the s-delocalization phenomenon of silane chains may greatly facilitate ET reactions will be tested. The starting material for the donor precursor, 4-(1,4-dimethoxynaphthyl)bromocyclohexane, was 1,4-naphthoquinone. After methylation and bromination, the Grignard reagent of the resulting bromide was reacted with cyclohexanedione, mono ethylene ketal. The resulting alcohol was changed to the donor precursor through the following functional group transformation steps: dehydration, hydrogenation, deketalization and bromination. 1,4-Dibenzyloxybromobenzene, the precursor for the acceptor, was synthesized from 1,4-hydroquinone through bromination and benzylation. The connection of the two precursors and either permethylated silane chains or permethylated alkyl chains will give the final target molecules for ET research. Progress on this is included.
Date: December 2000
Creator: Xiao, Wu
Partner: UNT Libraries

VISIBLE SPECTRA OF DICARBONYL SUBSTITUTED TRIS-BIPYRIDYL RUTHENIUM (II) COMPLEXES

Description: The solvent dependence of the metal-to-ligand charge-transfer band pattern of tris-bipyridyl ruthenium(II) derivatives with carbonyl substituents is attributed to a reduction in the energy required for electron transfer to the dicarbonylated bipyridyl ligand with an increase in solvent polarity.
Date: July 1, 1980
Creator: Ford, W.E. & Calvin, M.
Partner: UNT Libraries Government Documents Department

Low temperature carrier transport properties in isotopically controlled germanium

Description: Investigations of electronic and optical properties of semiconductors often require specimens with extremely homogeneous dopant distributions and precisely controlled net-carrier concentrations and compensation ratios. The previous difficulties in fabricating such samples are overcome as reported in this thesis by growing high-purity Ge single crystals of controlled {sup 75}Ge and {sup 70}Ge isotopic compositions, and doping these crystals by the neutron transmutation doping (NTD) technique. The resulting net-impurity concentrations and the compensation ratios are precisely determined by the thermal neutron fluence and the [{sup 74}Ge]/[{sup 70}Ge] ratios of the starting Ge materials, respectively. This method also guarantees unprecedented doping uniformity. Using such samples the authors have conducted four types of electron (hole) transport studies probing the nature of (1) free carrier scattering by neutral impurities, (2) free carrier scattering by ionized impurities, (3) low temperature hopping conduction, and (4) free carrier transport in samples close to the metal-insulator transition.
Date: December 1994
Creator: Itoh, K.
Partner: UNT Libraries Government Documents Department

Microbial Community Acquisition of Nutrients from Mineral Surfaces. Final Report

Description: Minerals and microbes undergo complex interactions in nature that impact broad aspects of near-surface Earth chemistry. Our primary objective in this project was to gain insight into how microbial species and communities acquire critical but tightly held nutrients residing on or within minerals common in rocks and soils, and to quantitatively study related microbe-mineral interactions including cell adhesion, electron transfer, and siderophore-mineral interaction processes.
Date: June 3, 2003
Creator: Hochella, M. F.
Partner: UNT Libraries Government Documents Department

Final report for DOE Project DE-FG02-89ER14062. Experimental studies of photoinduced charge carrier processes at semiconductor-electrolyte interfaces

Description: This study explored fundamental aspects of electron transfer reactions at electrode surfaces. Such fundamental knowledge is necessary for the development and implementation of improved photovoltaic, photochemical, and photoelectrochemical technologies. Two preprints are attached: ''Immobilization of cytochrome C at Au electrodes by association of a pyridine terminated SAM and the heme of cytochrome''; ''The nature of electronic coupling between ferrocene and gold through alkanethiolate monolayers on electrodes. The importance of chain composition, interchain coupling, and quantum interference.''
Date: September 1, 2001
Creator: Waldeck, David H.
Partner: UNT Libraries Government Documents Department

MICROSCALE METABOLIC, REDOX AND ABIOTIC REACTIONS IN HANFORD 300 AREA SUBSURFACE SEDIMENTS

Description: The Hanford 300 Area is a unique site due to periodic hydrologic influence of river water resulting in changes in groundwater elevation and flow direction. This area is also highly subject to uranium remobilization, the source of which is currently believed to be the region at the base of the vadose zone that is subject to period saturation due to the changes in the water levels in the Columbia River. We found that microbial processes and redox and abiotic reactions which operate at the microscale were critical to understanding factors controlling the macroscopic fate and transport of contaminants in the subsurface. The combined laboratory and field research showed how microscale conditions control uranium mobility and how biotic, abiotic and redox reactions relate to each other. Our findings extended the current knowledge to examine U(VI) reduction and immobilization using natural 300 Area communities as well as selected model organisms on redox-sensitive and redox-insensitive minerals. Using innovative techniques developed specifically to probe biogeochemical processes at the microscale, our research expanded our current understanding of the roles played by mineral surfaces, bacterial competition, and local biotic, abiotic and redox reaction rates on the reduction and immobilization of uranium.
Date: November 14, 2013
Creator: Beyenal, Haluk; McLEan, Jeff; Majors, Paul & Fredrickson, Jim
Partner: UNT Libraries Government Documents Department

Investigation of organometallic reaction mechanisms with one and two dimensional vibrational spectroscopy

Description: One and two dimensional time-resolved vibrational spectroscopy has been used to investigate the elementary reactions of several prototypical organometallic complexes in room temperature solution. The electron transfer and ligand substitution reactions of photogenerated 17-electron organometallic radicals CpW(CO){sub 3} and CpFe(CO){sub 2} have been examined with one dimensional spectroscopy on the picosecond through microsecond time-scales, revealing the importance of caging effects and odd-electron intermediates in these reactions. Similarly, an investigation of the photophysics of the simple Fischer carbene complex Cr(CO){sub 5}[CMe(OMe)] showed that this class of molecule undergoes an unusual molecular rearrangement on the picosecond time-scale, briefly forming a metal-ketene complex. Although time-resolved spectroscopy has long been used for these types of photoinitiated reactions, the advent of two dimensional vibrational spectroscopy (2D-IR) opens the possibility to examine the ultrafast dynamics of molecules under thermal equilibrium conditions. Using this method, the picosecond fluxional rearrangements of the model metal carbonyl Fe(CO){sub 5} have been examined, revealing the mechanism, time-scale, and transition state of the fluxional reaction. The success of this experiment demonstrates that 2D-IR is a powerful technique to examine the thermally-driven, ultrafast rearrangements of organometallic molecules in solution.
Date: December 16, 2008
Creator: Cahoon, James Francis
Partner: UNT Libraries Government Documents Department

DI-TERTIABYBUTYLNITROXIDE, A HILL REAGENT

Description: Di-tertiarybutylnitroxide (DTBN), which they have tried to use as a trapping agent to identify the species giving rise to the photo-induced EPR signals in photosynthetic materials, functions as a Hill reagent with spinach chloroplasts. Evidence is presented which indicates that the reduction of DTBN is affected by photosystem II of the electron transport system of spinach chloroplasts. The reduced form of DTBN, the hydroxylamine, undergoes a photo-oxidation with spinach chloroplasts. Possible explanations of this apparent inconsistency are presented. A product which could be ascribed to a chemical coupling reaction between the nitroxide and the radical species giving rise to the photo-induced EPR signals in spinach chloroplasts was not detected, even using radioactive tracer methods.
Date: January 1, 1970
Creator: Corker, Gerald A.; Klein, Melvin P.; La Font, Didier & Calvin,Melvin.
Partner: UNT Libraries Government Documents Department

QUANTUM CONVERSION IN PHOTOSYNTHESIS

Description: A new suggestion is made based on model work associated with similar measurements on the biological material itself. The primary quantum conversion act is an ionization occurring in a charge transfer complex. This is what it amounts to in chemical terms. But this process cannot occur in isolated charge transfer molecules in solution because the products cannot escape from each other. The primary quantum conversion as it occurs in modern photosynthesis can only take place in a laminated structure where the electrons and holes can escape from each other by electron migration and not by atomic migrations. This is the essential feature introduced here which differs from all the previous notions of how quantum conversion occurs in chemistry or biology.
Date: January 1, 1961
Creator: Calvin, Melvin
Partner: UNT Libraries Government Documents Department

CHEMICAL TRAPPING OF A PRIMARY QUANTUM CONVERSION PRODUCT INPHOTOSYNTHESIS

Description: The capacity of photosynthetic organisms to exhibit photo-induced electron paramagnetic resonance (EPR) signals has been known for over ten years. Subcellular units of photosynthetic materials, the quantasomes and the chromatophores, are capable of Hill Reaction activity, and also of exhibiting the light-induced EPR signals. This, coupled with the rapid rise and decay kinetics of these signals, suggests but does not prove that the unpaired electrons are involved in the initial electron transfer processes in the primary quantum conversion act. The identification of the species giving rise to these signals and their connection with processes of primary quantum conversion remains elusive even though such varied approaches as mutant strains, special growth conditions, extreme physical conditions, special metabolic inhibitors, etc. have been applied to this problem. In this communication the authors wish to report another method being used in an attempt to identify the species responsible for the unpaired electrons. Hoffman prepared a water soluble, stable free radical, di-tertiary-butylnitroxide (hereafter called DTBN), which is a 'vigorous free radical scavenger'. It shows a sharp, well resolved, symmetrical, three-line paramagnetic resonance spectrum that is relatively insensitive to the molecular environment. The chemistry of di-tertiary butylnitroxide has not been studied extensively. However, four distinct types of interaction can be envisioned for this molecule. It could undergo a one-electron reduction to form a hydroxylamine which can be reduced subsequently to the amine; an oxidative degradation to 2-methyl-2-nitrosopropane and isobutylene; or a coupling with another radical forming either an oxygen substituted hydroxylamine or a tri-substituted amine oxide.
Date: September 9, 1966
Creator: Corker, Gerald A.; Klein, Melvin P. & Calvin, Melvin.
Partner: UNT Libraries Government Documents Department

Melting of bcc Transition Metals and Icosahedral Clustering

Description: In contrast to polyvalent metals, transition metals have low melting slopes(dT/dP) that are due to partially filled d-bands that allow for a lowering of liquid phase energy through s-d electron transfer and the formation of local structures. In the case of bcc transition metals we show the apparent discrepancy of DAC melting measurements with shock melting of Mo can be understood by reexamining the shock data for V and Ta and introducing the presence of an icosahedral short range order (ISRO) melt phase.
Date: May 26, 2006
Creator: Ross, M; Boehler, R & Japel, S
Partner: UNT Libraries Government Documents Department

Design, Synthesis and Study of Dendrimers as Nanoscaffolds for Solar Energy Harvest

Description: Designing molecules in which the vectorial motions of charges can be controlled has been of significant research interest in the recent past. Covalent linear arrays of chromophores or other molecular assemblies such as liquid crystals, zeolites, polymers, peptides, and amphiphiles have all been used as components for this purpose. Significant amount of this effort also involved the use of dendrimers as the molecular architecture. The structural feature in which multiple functionalities are present in the periphery that decreases gradually as one moves towards the core renders dendrimers obvious candidates for light harvesting antenna. Most of the efforts reported in the literature are directed towards energy funneling from a chromophore in the periphery to another chromophore at the core of the dendrimer. There are relatively few reports that utilize the dendritic architecture for photoinduced charge separation, an important step in designing materials for photovoltaics. These reports focus mostly on conjugated molecular backbones. Since non-conjugated dendrimer backbones provide the possibility of independently tuning the electronic characteristics of the chromophore and the charge transfer unit and therefore carry out a systematic structure-property relationship study, we have designed and synthesized dendrimers
Date: January 25, 2008
Creator: Thayumanavan, Sankaran
Partner: UNT Libraries Government Documents Department