2 + 1 Chelating systems for binding organometallic fragment Tc(CO) 3+

Complexation of 99, 99m Tc(CO) 3 + organometallic fragment with 2 + 1 chelating systems was studied. HPLC analysis showed that the dithiocarbamate complexes of 99m Tc are stronger than their xanthate, acetylacetonate, and γ- methoxycarbonylmethylacetylacetonate analogs. To block the third vacancy in the technetium coordination sphere, we studied thiols, thioethers, primary and secondary amines, hydroxyl ion, imidazole, phosphines, and isocyanides. As determined by 99m Tc NMR spectroscopy, the mixed-ligand complexes Tc(CO)3(DTC)L (DTC is dithiocarbamate and L is isocyanide, imidazole, and phosphine) are the most stable to the histidine challenge reaction. HPLC analysis showed that, among these 2 + 1 systems, only the DTC-isonitrile system forms a single complex with 99m Tc(CO) 3 + . The minimal dithiocarbamate-isocyanide concentration providing complete binding of 99m Tc(CO) 3 + is 10-4 M. ©2005 Pleiades Publishing, Inc.