Grant: Research Tools and Instruments - Category 1 (<$150,000)

This application is to upgrade our existing pulsed electron paramagnetic resonance (EPR) spectrometer by adding to it a 1000 Watt power amplifier.  With our present pulsed spectrometer we can only acquire EPR spectra that have a range of approximately 10.0 Gauss.  Thus we are limited to organic free radicals that have very small hyperfine splittings and small anisotropic g tensors.  This upgrade will increase the spectral range of the spectrometer from 10.0 to approximately 1000.0 Gauss.    The upgrade is essential since the type of molecules the applicants are studying have large nuclear hyperfine splittings and large anisotropic g tensors.  J. Passmore is synthesizing sulfur and nitrogen free radicals that, in the solid state, act as molecular magnets.  R. Oakley is generating main group inorganic heterocyclic and organic free radicals.  When linked together they form solid state conducting materials.  S. Mattar is also studying S-N heterocyclic radicals that act as building blocks for compounds with novel magnetic properties. In addition, he generates paramagnetic half-sandwich organometallic reactive intermediates and isolates them in inert gas matrices at low temperatures. All three researchers correlate the structure and bonding of their compounds to their molecular properties. J. Spray is studying the composition of meteorites that are of pre-solar origin and contain mixtures of carbon free radicals and paramagnetic metal alloys. Understanding how these meteorites are formed may shed light on the evolution of the universe in its early stages.  In all cases, the free radical structures must be well characterized before their properties are understood.  Without EPR spectroscopy determination of their structures at the molecular level is not usually possible. EPR is a powerful technique that provides detailed information about the unpaired electron distribution and the environment of the nuclei without destroying the free radical.  Only with a pulsed EPR spectrometer can two-dimensional (2D) EPR experiments be performed where the structure of complex free radicals can be resolved and elucidated.  The success of our research is contingent on a pulsed high power EPR spectrometer.