Effectiveness of CrIII, MnII, CoII and NiII paramagnetic complexes in promoting the ortho- into para-positronium conversion reactions

Abstract

The conversion reactions of ortho- into para-positronium, Ps, atoms promoted by Cr^II complexes with water, urea and ethylenediaminetetraacetic acid, by the complexes of Cr^III, Co^II and Ni^II ions with ethylenediaminetetramethylene-phosphonic acid, nitrilotrismethylene-phosphonic acid, urea and by the complexes of Mn^II ions with urea, glycine and iminodiacetic acid have been investigated in order to ascertain the role of the metal ion in the reactions. All the complexes considered are octahedral and of high spin type. The reaction rate constants of the complexes are correlated to the corresponding electron delocalization caused by the ligands as described by the ratio B/B₀=β between the inter-electronic repulsion parameters in complexed and free gaseous metal ions. The rate constant per fully delocalized unpaired electron of the metal ion was deduced and found to be (3.7 ± 0.6) dm³ mol^–1n s^–1 electron^–1.