Complexation of NpO2+ by aromatic polycarboxylates

The complexation of Np(V) with aromatic polycarboxylic acids was studied by spectrophotometry at 1 M ionic strength (NaClO4) and 23 degrees C. The stability constants of the 1:1 complexes decreased in the order hemimellitate>mellitate>pyromellitate>trimellitate approximate to phthalate). After correction for statistical effects, the stability constants with all ligands except hemimellitate were approximately the same. For all systems, the data corresponded to bidentate chelation by the ligand. The greater strength of hemimellitate complexation was attributed to an increase in electron density at the binding site through induction from the non-chelating carboxylate group. (C) 1998 Elsevier Science S.A.