“…The linewidth of 59 Co NMR signals is a consequence of quadrupolar relaxation and is therefore a function of the electric field gradient at the nucleus and the rotational correlation time of the complex. 88,106 For tetragonal complexes, the 59 Co chemical shift exhibits an inverse, linear correlation with the ligand field splitting of the complex after adjusting for the nephelauxetic effect of the ligands. 82,83,85,86 Thus, 59 Co NMR spectroscopy provides a method to probe both the electron donating capacity and the nephelauxetic properties of the ligand scaffolds.…”