Electron Delocalization in 3d Complexes Caused by Dimethylurea Checked by Positron Annihilation

The rate constants, k _CR, of ortho- into para-positronium conversion reactions promoted by paramagnetic 3d complexes are linearly correlated with the electron delocalization, , of unpaired metal electrons caused by ligands, being the ratio between the inter-electronic repulsion parameters in complexes and in the free gaseous ions. By applying a procedure previously described the values of Mn^II, Co^II, Ni^II complexes with dimethylurea were deduced from the mentioned correlations and compared with those of complexes with urea obtained both by the method of Ps reactions here applied and that based on UV-Vis absorption spectroscopy.