‘2+1’ Tricarbonyltechnetium(I) and -rhenium(I) mixed-ligand complexes with N-methylpyridine-2-carboxyamide and isocyanide or imidazole ligands—potential precursors of radiopharmaceuticals

Complexes of tricarbonyltechnetium(I)-99 m and rhenium(I)-188, of ‘2+1’ type: with N-methylpyridine-2-carboxyamide as a neutral bidentate ligand and either tert-butyl 3-isocyanopropionate or imidazole as a monodentate ligand, have been obtained on n.c.a. level. The complexes exhibit moderate lipophilicity and rather high stability in neutral aqueous solutions. The latter has been evidenced from the tests on histidine/cysteine challenge and on protein binding in rat serum. The rhenium complexes studied are much more stable than their technetium analogues. The isocyanopropionate complex may be considered promising model for radiopharmaceutical precursors.