A multinuclear NMR study of the complexation of W(VI) with meso-2,3-dimercaptosuccinic acid (DMSA)

Meso-2,3-dimercaptosuccinic acid (DMSA), which is used as an antidote for h eavy metal poisoning and in complexes of Tc-99m for diagnostic purposes, fo rms several complexes with tungsten(VI) in aqueous solutions, as found by H -1, C-13, O-17 and W-183 NMR spectroscopy. In the pH range similar to 4-7, there are four complexes in which the acid acts as a bidentate ligand throu gh one carboxyl group and the adjacent sulfhydryl group (a dominant 2:2 spe cies and three 1:2 metal-ligand isomers are proposed) and 2:1 complexes in which the ligand is twisted in order to use the four binding groups. It is proposed that in both the 2:2 and 2:1 cases the S atoms bridge the two W at oms. At lower pH, the acid is again predominantly a tetradentate ligand in m:n associations with the metal (m>n). (C) 2000 Elsevier Science Ltd All ri ghts reserved.