SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF TECHNETIUM AND RHENIUM COMPLEXES CONTAINING DERIVATIZED AMINO-ACIDS

A novel N2S tridentate ligand system (H2Ln) for the formation of Re-V= O, Tc-99(V)=O and Tc-99(V)=N complexes has been synthesized. N-Protect ed amino acids conjugated with S-methyl 2-methyldithiocarbazate gave c helate complexes [MO(L-n)Cl] (M=Tc or Re) and [TcN(L-n)(PPh3)] in whic h H2Ln are doubly deprotonated. All the compounds have been characteri zed by elemental analysis, IR and NMR spectroscopy and for [TcO(L-2)Cl ] and [TcN(L-4)(PPh3)] crystal structures determined. Both possess a d istorted square-pyramidal geometry with the oxygen or nitrogen atom in the apical position, the tridentate ligand and a Cl- ion or PPh3 grou p forming the basal plane respectively. A study of reactivity shows th at the formation of complexes can be related to the N-protecting group s, the alkyl substituent on the C-alpha atom and the metal precursors. Circular dichroism measurements on Re-V=O complexes have been perform ed in order to investigate possible conformational variations in solut ion. Finally, although the presence of isomers is possible, NMR spectr oscopy has shown that they are absent at room temperature.