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2013 Chemistry Newsletter
The Department of Chemistry Newsletter is now available.
Read 2013 Newsletter
2013 Beckman Scholars Program
The UO Chemistry Department will be awarding prestigious Beckman Research Scholarships to qualifying undergraduate research students. 2013 Beckman Scholars Information
B.S., Purdue University, 1975. Ph.D., California Institute of Technology, 1979 (Harry Gray). Honors and Awards: Alfred P. Sloan Fellow, 1986-88. American Association for the Advancement of Science Fellow, 2010. At Oregon since 1985.
The research in Tyler’s laboratory focuses on mechanistic organometallic and inorganic chemistry, polymer chemistry, catalysis, and photochemistry.
In one project, we are studying aqueous phase homogeneous catalysis. Our group is using its expertise in synthesis to modify organometallic catalysts so they are water-soluble. The reason for doing this is that water is an environmentally benign solvent, so there is a big push to convert many catalytic processes from organic solvents to water. One overall goal of our research is to investigate differences in the reaction mechanisms between water and organic solvents. In recent studies, we discovered active catalysts for nitrile hydration, olefin polymerization, olefin hydration, carbonylations, and assorted C-H bond activation reactions – all in aqueous solution
Proposed mechanism for the hydration of nitriles with Cp'2Mo(OH)(OH2)+
Another system under investigation is the reaction of nitrogen and hydrogen to form ammonia at low temperature using water-soluble organometallic and coordination complexes as catalysts in aqueous solution. This project has led to a number of surprises, particularly concerning the remarkable ability of H2 to act as a ligand in aqueous solution. The scheme below shows a system we recently discovered that reacts H2 with N2 to form ammonia at room temperature and atmospheric pressure. Efforts are underway to improve the efficiency of this reaction and to understand the reaction mechanism.
X-ray crystal structure of the Fe(DMeOPrPE)2Cl2 complex.
Yet another project in the general area of aqueous organometallic chemistry is our synthesis of water-soluble phosphine complexes that reversibly bind dinitrogen. Dinitrogen is a major contaminant in natural gas and our research is aimed at finding complexes that bind dinitrogen at high pressure and release it at low pressure. The goal is to use these complexes as scrubbers for removing dinitrogen from natural gas, thus making available a sizable fraction of our country’s natural gas reserves for energy use. In a similar project with a related goal, we are studying catalytic methods for removing sulfur from petroleum. An especially innovative aspect of this desulfurization project is our use of microscale reactors to enhance the separation.
Another project underway in our laboratory is the synthesis and study of polymers that are photochemically degradable with visible light. It is noteworthy that photochemically degradable polymers have many potential uses in environmental applications, in medicine, and in materials science – but only if a way can be found to control the onset of photodegradation.
A photodegradable polyurethane
Our goal is to design polymers in which we can control the onset of photodegradation. Perhaps not surprisingly, there are a number of factors that control the onset and rate of polymer photodegradation, and our research is quantifying how each of these factors influences polymer photodegradation. Among the various factors that affect degradation, our work suggests that the “radical cage effect” is especially important in determining the rate of polymer decomposition. To probe the cage effect, we are doing femtosecond time-scale laser pump-probe studies on a variety of polymers and oligomers to investigate the relationship between the magnitude of the cage effect and the rate of photodecomposition. Our mechanistic investigations of the radical cage effect have led to many fundamental discoveries, such as an example of “in-cage” radical trapping by an agostic hydrogen interaction.
Preparation of Photoreactive Oligomers by ADMET Polymerization of [(C5H4(CH2)8CH=CH2)Mo(CO)3]2. Ginger V. Shultz, Jennifer M. Zemke, and David R. Tyler. Macromolecules, 2009, 42, 7644-7649.
Precursors to Dinitrogen Reduction: Structures and Reactivity of trans-[Fe(DMeOPrPE)2(η2-H2)H]+ and trans-[Fe(DMeOPrPE)2(N2)H]+. Justin L. Crossland, Douglas M. Young, Lev N. Zakharov, and David R. Tyler. Dalton Trans. 2009, 9253-9259.
Investigation of the Reactivity of Pt Phosphinito and Molybdocene Nitrile Hydration Catalysts with Cyanohydrins. Takiya J. Ahmed, Brandy R. Fox, Spring Melody M. Knapp, Robert B. Yelle, J. Jerrick Juliette, and David R. Tyler. Inorganic Chemistry 2009, 48, 7828-7837.
Intermediates in the Reduction of N2 to NH3: Synthesis of Iron η2 Hydrazido(1-) and Diazene Complexes. Justin L. Crossland, Chantal G. Balesdent, and David R. Tyler. Dalton Trans. 2009, 4420-4422.
Aqueous Coordination Chemistry of H2. Why is Coordinated H2 Inert to Substitution by Water in trans-Ru(P2)2(H2)H+-type Complexes (P2 = a Chelating Phosphine)? Nathaniel K. Szymczak, Dale A. Braden, Justin L. Crossland, Yevgeniya Turov, Lev N. Zakharov, and David R. Tyler. Inorg. Chem. 2009, 48, 2976-2984.
Theoretical Studies of N2 Reduction to Ammonia in Fe(dmpe)2N2. Robert B. Yelle, Justin L. Crossland, Nathaniel K. Szymczak, and David R. Tyler. Inorganic Chemistry 2009, 48, 861-871.
Application of a Perrin-like Kinetics Model to Explain the Biphasic Photochemical Degradation Rates of Polymers. Bevin C. Daglen and David R. Tyler. Macromolecules, 2008, 41, 9525-9531.
Aspects of Dihydrogen Coordination Chemistry Relevant to Reactivity in Aqueous Solution. Nathaniel K. Szymczak and David R. Tyler. Coord. Chem. Rev., 2008, 252, 212-230.
Effect of Solvent on the Dimerization of the ansa-Molybdocene Catalyst [C2Me4Cp2Mo(OH)(OH2)][OTs]. Takiya J. Ahmed and David R. Tyler. Organometallics, 2008, 27, 2608-2613.
Solvent Cage Effects: The Influence of Radical Mass and Volume on the Recombination Dynamics of Radical Cage Pairs Generated by Photolysis of [CpCH2CH2N(CH3)C(O)(CH2)nCH3Mo(CO)3]2 (n = 3, 8, 13, 18) (Cp = η5-C5H4) Complexes. Alan B. Oelkers, Erick J. Schutte and David R. Tyler. Photochem. Photobio. Sci., 2008, 7, 228-234.
Radical Cage Effects: A Method for Measuring Recombination Efficiencies of Secondary Geminate Radical Pairs using Pump-Probe Transient Absorption Methods. Alan Oelkers and David R. Tyler. Photochem. Photobio. Sci. 2008, 7, 1386-1390.
Femtosecond Pump-Probe Transient Absorption Study of the Photolysis of [Cp'Mo(CO)3]2 (Cp' = η5-C5H4CH3); The Role of Translational and Rotational Diffusion in the Radical Cage Effect. Alan B. Oelkers, Lawrence F. Scatena, and David R. Tyler. Journal of Physical Chemistry A, 2007; 111(25),; 5353-5360.
Transition Metal-containing Polymers by ADMET; Polymerization of cis-Mo(CO)4(Ph2P(CH2)3CH=CH2)2. Ginger V. Shultz, Lev N. Zakarahov and David R. Tyler, Macromolecules 2008, 41, 5555-5558.
The Effect of Morphology Changes on Polymer Photodegradation Efficiencies. A Study of Time-Dependent Morphology and Stress-Induced Crystallinity. Bevin C. Daglen and David R. Tyler. Journal of Inorganic and Organometallic Polymers and Materials 2009, 19, 91-97.
Reduction of N2 to Ammonia and Hydrazine Utilizing H2 as the Reductant. John D. Gilbertson, Nathaniel K. Szymczak, and David R. Tyler, J. Am. Chem. Soc. 2005, 127, 10184-10185.
Organometallic Chemistry in Aqueous Solution. Reactions Catalyzed by Water-Soluble Molybdocenes. Kerry L. Breno, Takiya J. Ahmed, Michael D. Pluth, Christoph Balzarek, and David R. Tyler, Coordination Chemistry Reviews, 2006, 250, 1141-1151.
Solution Chemistry of a Water-Soluble _2-H2 Ruthenium Complex: Evidence for Coordinated H2 Acting as a Hydrogen Bond Donor. Nathaniel K. Szymczak, Lev N. Zakharov, and David R. Tyler. J. Am. Chem. Soc., 2006, 128, 15830-15835.
Detection of hydrogen bonding in solution: A 2H nuclear magnetic resonance method based on rotational motion of a donor/acceptor complex. Nathaniel K. Szymczak, Alan B. Oelkers, and David R. Tyler. Physical Chemistry Chemical Physics, 2006, 4002-4008.
Coordination Chemistry of H2 and N2 in Aqueous Solution. Reactivity and Mechanistic Studies using trans-FeII(P2)2X2-type Complexes (P2 = a Chelating, Water-Solubilizing Phosphine). John D. Gilbertson, Nathaniel K. Szymczak, Warren K. Miller, David K. Lyon, Bruce M. Foxman, Joclyn Davis, David R. Tyler. Inorg. Chem., 2007, 46, 1205 -1214.
Femtosecond Pump-Probe Transient Absorption Study of the Photolysis of [Cp'Mo(CO)3]2 (Cp' = h5-C5H4CH3); The Role of Translational and Rotational Diffusion in the Radical Cage Effect. Alan B. Oelkers, Lawrence F. Scatena, and David R. Tyler. Journal of Physical Chemistry A, 2007; 111(25); 5353-5360.
The Radical Cage Effect; Is There a Spin Barrier to Recombination of Transition Metal Radicals? John D. Harris, Alan B. Oelkers, and David R. Tyler. J. Am. Chem. Soc., 2007, 129(19); 6255-6262..
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