R. Linn Belford

Professor R. Linn Belford was awarded the B.S. in chemistry by the University of Illinois in 1953 and the Ph.D. in chemistry by the University of California (Berkeley) in 1955. Since then, he has been on the faculty at Illinois, where he has exploited spectroscopy and electronic magnetic resonance techniques to characterize transition metal ions, radicals, disordered materials, and catalytic surfaces. He has received NSF, Alfred P. Sloan, and NIH fellowships, and is currently a director of the Illinois EPR Research Center. His research interests are in physical, inorganic, and biophysical chemistry.

This group focuses on structures in disordered solids, solutions and crystals, and on some aspects of dynamics in these materials. The Illinois EPR Research Center (IERC) is a national research resource which provides us with unique opportunities to apply advanced electronic magnetic resonance techniques (electron para-magnetic resonance (EPR)) to these problems. In the IERC, we have developed the world's first S-band (2-4 GHz) pulsed EPR, which is used to study very weak interactions between a free radical or transition metal ion and a remote atom. We have also developed the first high-sensitivity 3 cm-1 (very high frequency) EPR spectrometer with wide sweep and cryostatic capability, which provides exquisite resolution of nearly-identical radical species and of anisotropies and permits characterization of species, such as many metallo-proteins, which have very large zero-field splittings.

Electric quadrupole coupling of nuclei at paramagnetic centers can be measured through its effect on electron paramagnetic resonance spectra. One set of studies in our research group involves the investigation of experimental techniques for measurement of the striking correlations between nuclear quadrupole coupling and structural features at the magnetic site, and of theories of both measurement and interpretation. Other current applications of EPR and related spectroscopies in our group include: (1) systematic studies of spin lifetime in paramagnetic relaxation agents used for NMR imaging; (2) electron-electron coupling between different sites; (3) use of unpaired electrons native to carbonaceous materials as probes of their complex molecular structures; (4) use of unpaired electrons to probe catalytic surfaces and internal interfaces in materials; (5) fast (picosecond) dynamics in condensed phases; (6) metalloprotein structures; (7) paramagnetic sensors for oxygen and nitric oxide.

Throughout our EPR work, this group makes use of special techniques. Much attention has been given to full computer simulation analyses of complex spectra; new theories and improvements on traditional computational methods are developed to make some of the more difficult analyses tractable. We employ a wide range of spectroscopic frequencies and magnetic fields, with very low frequencies (~0.03 cm-1 or less) and fields (~100 G) favoring non-Zeeman effects and very high frequencies (> 3 cm-1), and fields (up to 70,000 G, with sweeping superconducting magnets) accentuating Zeeman splittings and high transition probabilities. Electron spin echo (ESE) spectroscopy is a rapid pulsed EPR technique which we employ to study very small hyperfine couplings and local structure in disordered materials. Electron-nuclear double resonance (ENDOR) is a method used to probe intermediate hyperfine couplings and, in effect, do NMR studies on paramagnetic centers. In both techniques, we use magnetic field position to select specific molecular orientations.

Representative publications

Wiener, E.C., Auteri, F.P., Chen, J.W., Brechbeil, M.W., Gansow, O.A., Schneider, D.S., Belford, R.L., Clarkson, R.B., and. Lauterbur, P.L., "Molecular Dynamics of Ion-Chelate Complexes Attached to Dendrimers," J. Am. Chem. Soc., 118:77 79-7782, 1996.