Stability studies on 99mTechnetium(III) complexes with tridentate/monodentate thiol ligands and phosphine ('3+1+1' complexes)

The preparation and characterisation of 3+1+1 technetium complexes of the general formula [Tc(SES)(RS)(PMe2Ph)] (SES = tridentate dithiol ligand, E = S, O, NMe; RSH = monothiol ligand) at the n.c.a. level is described. The Tc(III) complexes are prepared in a one-step procedure starting from pertechnetate in yields of 85-95% of radiochemical purity. A comparison of their chromatographic data with the fully characterised Tc-99 complexes indicate the identity of the investigated compounds. Stability studies show that the Tc-99m complexes undergo some alteration in solution. They are oxidised to the 3+1 oxotechnetium (V) complexes and/or decompose in aqueous solution. In challenge experiments performed with glutathione, exchange of the monothiolato ligand occurs in the same manner as known for the 3+1 complexes. (C) 2000 Elsevier Science Ltd. All rights reserved.