High-field Pulse Electron Paramagnetic Resonance (EPR) has recently emerged as a powerful technique in the study of chemical, biological and materials systems (1,2). It represents a sensitive, non-invasive, site-selective spectroscopy for the analysis of both molecular and macroscopic properties. With the support of the Australian Research Council and the Max Planck Institute for Chemical Energy Conversion in Mülheim (Germany), we are establishing Australia’s first high-field (3 T, 94 GHz, W-band) pulse EPR facility in Canberra as part of a cross-university EPR platform involving ANU, USyd, UNSW, UoW and UQ. This facility is designed to serve EPR spectroscopists across Australia and will be unique in the Asia-Pacific region. Performing EPR at higher magnetic fields enhances sensitivity, due to the increased spin polarization and spectral resolution, as seen in nuclear magnetic resonance (1). The high-field regime also extends the range of systems amenable for study, such as high spin or integer-spin systems which are often considered EPR silent. More importantly, it allows implementation of new cutting-edge multidimensional pulse EPR methods such as ELectron-electron DOuble Resonance (ELDOR)-detected NMR (EDNMR) and related techniques, which has recently been demonstrated to provide quantitative detection of all magnetic nuclei of paramagnetic systems (3,4).
The state-of-the-art W-band instrument, to be commissioned in early 2018, represents a modified-commercial platform, optimized for the study of difficult (broad, fast relaxing) species such as transition metals. Key improvements to the instrument include a redesigned microwave bridge (400 mW) of superior stability to those commercially available and flexible, purpose-built broadband (100 MHz) probeheads with optimized performance for specific sample types (3). The diverse applications that this instrument has in the areas of structural biology, solvation science and catalysis are described using a series of examples. Coupling EPR measurements to electrochemistry and kinetic experiments is also outlined.