Abstract In order to develop a redox delivery system for Tc radiotracers the synthesis of new nicotinamide and pyridinium salt-substituted Re (V) mixed-ligand complexes of the '3+ 1'type is described. The complexation of 99/99m Tc with these ligands was studied by thin layer chromatography and UV-VIS spectroscopy. The reduction of the pyridinium salt with sodium dithionite to the 1, 4-dihydropyridine was carried out on the free ligand and on the ...