Speciation of pentavalent technetium complexes with aniline and thiobenzene derivatives

The reaction of bidentate aniline oligomers with pentavalent technetium has been investigated previously through the reaction of (n-Bu4N)TcOCl 4 with o-phenylenediamine (PDA). The initial studies found that PDA reacted in a 1 to 2 molar ratio with pentavalent technetium in in ethanol. This study was expanded by the examination of a second aniline derivatives, 2-aminophenol (AMP)) and two thiobenzene derivatives (2-mercaptophenol (MP) and thiosalicylic acid (TSA)) to evaluate the kinetic formation of these complexes with pentavalent technetium. The pentavalent technetium complexes all showed reactivity with technetium having a coordination numbers of 5 with all ligands reacting in a 1 to 2 metal to ligand ratio, which was confirmed by the use of electrospray ionization mass spectrometry (ESI- MS). Kinetic measurements were performed by UV-visible spectroscopy in a 24 hours period. Separate spectra were also obtained of the metal ligand complex at varying ratios of metal to ligand concentration to determine extinction coefficients for each metal-ligand complex based on Beer-Lambert's equation. While most of the reactions took about 24 hours to reach completion, the complex of TcO(TSA)2 - has the fastest formation rate while the TcO(PDA)2 - had that fastest reaction rate for the analine derivatives.