Effect of covalency on the electron-nuclear dipolar relaxation in paramagnetic complexes

The calculation of NMR relaxation rates due to electron-nuclear dipolar interaction in paramagnetic complexes was extended to include the distribution of the electronic unpaired spin density on the metal and the ligant orbitals. Numerical calculations were performed for the proton relaxation rates of hexamine ruthenium III ion using various choices for its wavefunctions. While the effect of the distribution of the spin density on the ruthenium d orbitals was small, the spin derealization to the ligand orbitals increased significantly the calculated dipolar interaction relative to the point dipole value. The numerical values are in good agreement with the available experimental data.