A PRACTICAL STRATEGY FOR DETERMINATION OF PROTON HYPERFINE INTERACTION PARAMETERS IN PARAMAGNETIC TRANSITION-METAL ION COMPLEXES BY 2-DIMENSIONAL HYSCORE ELECTRON-SPIN-RESONANCE SPECTROSCOPY IN DISORDERED-SYSTEMS

A practical strategy is outlined for the determination of proton hyper fine parameters in paramagnetic transition metal ion complexes in diso rdered systems from a single two-dimensional hyperfine sublevel correl ation spectroscopy (2D HYSCORE) electron spin resonance experiment. Bo th dipolar and isotropic hyperfine interaction parameters can directly be determined from the cross peak ridges in the HYSCORE spectrum in t he limit of the point dipole approximation. This approach is justified by spectral simulations for isotropic and axially symmetric g tensors . If the HYSCORE spectrum is measured at the gl spectral region of the electron spin resonance powder spectrum, the orientation of the hyper fine interaction tensor with respect to the g tensor frame can also be deduced from the shape of the cross peak ridges in many cases. Two ex perimental examples are presented. Using this approach, the hyperfine interaction parameters for protons in [CU(H2O)(6)](2+) and in [CU(C5H5 N)(4)](2+) complexes, both incorporated into mesoporous (L)Cu-MCM-41 s ilica tube material, are determined from a single 2D HYSCORE spectrum; The parameters are in good agreement with independent measurements by electron spin echo modulation spectroscopy.