Manganese paramagnetism

In 1948, Bloch, Hansen, and Packard reported first the use of a paramagnetic salt, ferric nitrate to enhance the relaxation rates of water protons (8). In 1987, Lauterbur et al. (9) applied a manganese(II) salt to distinguish between different tissues based on the differential relaxation times. The first commercial MRI... 

Schwendener, R. A., Wuethrich, R., Duewell, S., Westera, G., and Von-Schulthess, G. K. Small unilamellar liposomes as magnetic resonance contrast agents loaded with paramagnetic manganese-, gadolinium-, and iron-DTPA-stearate complexes. Int. J. Pharm. 1989, 49, 249-259. 

Robert and Meunier have isolated and characterized covalent adducts of metallopor-phyrins with artemisinin. Initial attempts using an iron(II) heme model were inconclusive, since the strong paramagnetism of the iron did not allow detailed characterization of the adduct and attempts at demetallation resulted in its degradation. Therefore, manganese(II) tetraphenylporphyrin (TPP) was used since it required milder demetallation conditions and the adduct 50a was formed. The suggested mechanism for the alkylation involves a pendent ethyl radical 50 (Scheme 13). 

MnS2 antiferromagnetic (7n=78 K), insulator above 7n paramagnetism fits five unpaired electrons per manganese. 

---