Formation constants of binary complexes of lanthanides with 2-hydroxymethyl-benzimidazole

Proton-ligand and metal-ligand formation constants of binary complexes of La(III), Pr(III), Nd(III), Gd(III), Dy(III) and Y(III) with 2-hydroxymethylbenzimidazole have been determined pH-metrically in 50 per cent v/v aq dioxane medium at 30deg, 40deg and 50degC and I=0.1 M (NaClO4). The theromdynamic parameters of complex formation have been evaluated. Stabilities (log β2 values) of the chelates increase with decrease in ionic radius of the metal [Dy(III) > Gd(III) > Y(III) > Nd(III) > Pr(III) > La(III)]. (author). 7 refs