Partenaires

CNRS


Rechercher


Accueil > Publications > Recherche par années > Années 1990 > 1994

Toth, E ; Brucher, E ; Lazar, I ; Toth, I

Kinetics of formation and dissociation of lanthanide(iii)-dota complexes

Inorganic Chemistry 33 (18) 4070-4076

par Administrateur - publié le

Abstract :

The formation rates of Ce(DOTA)-, Eu(DOTA)-, and Yb(DOTA)- have been studied at 25-degrees-C and I = 1.0 M (NaC1) by spectrophotometry (Ce3+, Eu3+) and an indicator method (Yb3+). (H4DOTA = 1,4,7,10-tetraazacyclododecane-N,N’,N’’,N’’’-tetraacetic acid). In the formation reaction, a diprotonated intermediate, Ln(H2DOTA)+, is formed very rapidly and slowly rearranges to the product. The intermediates Ce(H2DOTA)+ and Eu(H2DOTA)+ have been detected by spectrophotometry. The stability constants of the intermediates were determined by pH-metry and spectrophotometry. H-1-NMR studies indicate that, in the diprotonated intermediates, only the carboxylate groups are coordinated to the metal ions. The rearrangements of the intermediates occuring by the loss of two protons are OH- ion catalyzed processes.