Technetium and rhenium: coordination chemistry and nuclear medical applications

Coordination compounds of the radioactive element technetium are well established in diagnostic nuclear medicine, and various complexes of the gamma-emitting nuclide 99mTc are routinely used for organ imaging. Modern trends in the radiopharmaceutical chemistry of technetium focus on the 'labeling' of biologically active molecules such as peptides, steroids or other receptor-seeking units. This requires more knowledge about the coordination chemistry of the artificial transition metal, particularly with regard to stable or kinetically inert coordination spheres, which allow couplings to biomolecules following a bioconjugate approach. The dominant role of technetium compounds in diagnostic procedures recommends the beta--emitting rhenium isotopes 186Re and 188Re for applications in nuclear-medical therapy. 188Re is readily available from an 188W/188Re radionuclide generator system and general synthetic approaches can be adopted from the established technetium chemistry.