Reactivity of technetium(I) thioether carbonyl complexes towards histidine- An EXAFS study in solution

Technetium(l) thioether carbonyl complexes and their reaction products with histidine were prepared and characterised by Extended X-ray Absorption Fin e Structure (EXAFS) spectroscopy, various chromatographic and electrophoret ic methods and electrospray mass spectrometry. Their behaviour in aqueous s olutions was studied on the carrier-added (Tc-99) and the no-carrier-added (Tc-99m) levels. HPLC and electrophoretic studies show the identity of reac tion products at both concentration levels. Technetium(l) carbonyl complexe s containing a bidentate dithioether ligand [Tc(CO)(3)Cl(S-S)], as wen as a tridentate carboxylato thioether ligand [Tc(CO)(3)(S-S-O)], undergo a liga nd exchange reaction with histidine and form the complex [Tc(CO)(3)His]. EX AFS measurements were performed to estimate the structural parameters of th e dissolved technetium(I) carbonyl complexes and their reaction products, a fter the challenge experiments. The calculated bond lengths and coordinatio n numbers are in agreement with the expected values and confirm the ligand exchange reactions. (C) 2001 Elsevier Science B.V. All rights reserved.