Guest Seminar

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Date
02/21/2019 3:30 pm - 5:00 pm
Location

Description

Dr. Joshua Tesler
Northwestern University
 
ADVANCED PARAMAGNETIC RESONANCE SPECTROSCOPY OF HIGHSPIN TRANSITION METAL ION COMPLEXES
 
Abstract: We will discuss the inorganic chemistry applications of advanced paramagnetic resonance techniques. These
techniques include electron paramagnetic resonance (EPR), but rather than being performed at a fixed, low frequency (typically Xband,
~9 – 9.5 GHz) and a modest field sweep (typically 0 – 600 mT), the technique of interest involves variable, high frequencies
(up to 1 THz) and field sweeps from zero up to 36 T This technique is referred to as high-frequency and -field EPR (HFEPR).
Another technique is far-infrared magnetic resonance (FIRMS), which involves fixed external fields from 0 – 7 T, with FIR
frequencies in the range of 20 – 200 cm (or higher using a conventional FTIR). HFEPR and FIRMS are applied to high-spin
(defined here for EPR purposes as S > 1/2) mononuclear transition metal ion complexes. Particular emphasis will be placed on
those ions that belong to the non-Kramers (integer-spin) class and are typically “EPR-silent” at X-band due to large magnitude
zero-field splitting (zfs). Classic examples of this type include: V3+ (3d2, S = 1), Mn3+ (3d4, S = 2), Fe2+ (3d6, S = 2), and Ni2+ (3d8,
S = 1). From among these ions, Mn3+ will be the primary example (see Figure 1). HFEPR is also useful for investigating high-spin
Kramers-type (half integer-spin) ions characterized by large zero-field splitting. Examples of these are Cr3+ (3d3, S = 3/2), Fe3+
(3d5, S = 5/2), and Co2+ (3d7, S = 3/2), of which the last will be used for illustration. The meaning and utility of the parameters
extracted by HFEPR/FIRMS will be explained. This information, in concert with quantum chemical theory, helps understand the
electronic structure transition metal ion complexes both as models for enzymatic active sites and as building blocks for molecular
(single ion) magnets.
 
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. He has pursued these interests
both at by continuing work at Northwestern using EPR/ENDOR instrumentation developed by Prof. Hoffman and
his research group and at the National High Magnetic Field Laboratory (NHMFL) using their high-frequency and -
field EPR (HFEPR) instrumentation.

Location information

Chemistry Seminars

Country
United States
County
Payne
City
Stillwater 74078
Street
103 Physical Sciences