Friday, February 16, 2018
Dr. Joshua Telser
Department of Biological, Chemical, and Physical Sciences
Hand 1144, 3:30 PM
Abstract: We will discuss recent experiments in the area of high-frequency and -field electron paramagnetic resonance (HFEPR) of high-spin (defined here as S > 1/2) mononuclear transition metal ion complexes. Particular emphasis will be placed on those paramagnetic metal ions that belong to the non-Kramers (integer-spin) class and are typically 'EPR-silent' at conventional frequencies and fields (X- or Q-band = 35 GHz) due to a large magnitude of zero-field splitting. Examples of this class are V(III) (3d2, S = 1), Mn(III) (3d4, S = 2), Fe(II) (3d6, S = 2), and Ni(II) (3d8, S = 1), which have now been successfully detected by HFEPR and thoroughly characterized in a variety of coordination configurations. We will also discuss advantages that HFEPR can bring into spectroscopy of high-spin Kramers-type (half integer-spin) ions characterized by large zero-field splitting, such as Co(II) (3d7, S = 3/2). We will describe a tunable-frequency HFEPR methodology based on variable-frequency sources that allows accurate determination of spin Hamiltonian parameters from powder spectra. We will also introduce the application of coherent synchrotron radiation (CSR) for extending frequency-domain EPR into the THz region. Finally, we will touch upon the meaning and/or utility of spin Hamiltonian parameters for the determination of the electronic structure of the transition metal ion complexes discussed above within the two aspects: (a) as models for enzymatic reaction centers, and (b) as building blocks for molecular magnets.
Krzystek, J.; Telser, J.; "Measuring giant anisotropy in paramagnetic transition metal complexes with relevance to single-ion magnetism"; Dalton Trans. 2016, 45, 16751–16763. (Perspectives article; DOI: 10.1039/C6DT01754A).
Bio: Joshua Telser, Associate Professor of Chemistry at Roosevelt University (Chicago, IL, USA), graduated from Cornell University (Ithaca, NY) with a B.A. in chemistry in 1980. He pursued his graduate studies in inorganic chemistry at the University of Florida (Gainesville, FL), where he received a Ph.D. in 1984 under the direction of the late Prof. Russell S. Drago. There followed an NIH postdoctoral fellowship in bioinorganic chemistry at Northwestern University (Evanston, IL) with Prof. Brian M. Hoffman. After a period in industrial and academic research, he joined the faculty of Roosevelt University in 1990 where he currently teaches general chemistry and various courses related to inorganic chemistry. Prof. Telser has long been interested in paramagnetic molecular systems having relevance to inorganic chemistry, materials science, and biology.
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