Quantitative Mapping of Metal-Centered Dipolar Field in Hemin Dicyano Complex by Solution NMR

The metal-centered pseudo-contact shift contribution in the hyperfine shift of NMR resonance of paramagnetic hemin dicyano complex ([FeIII(proto)(CN)2]) in solution was quantitatively determined from the combined use of 1H and 13C NMR data. Taking advantage of the axially symmetric magnetic property for [FeIII(proto)(CN)2] in solution, the paramagnetic metal-centered dipolar field was quantitatively mapped. The highly solvent-dependent magnetic anisotropy, (g2⁄⁄–g2⊥), of this complex in CD3OD was estimated to be 7.2 and the obtained value is placed between the values in D2O (4.4) and in CDCl3 (9.7).