The mixed ligand [2+1] approach: An easier way of labeling the [M(CO)3]+ core (M=99,99MTC, RE)?

Abstract Within the mixed ligand [2+1] approach several model complexes of the general formula [99mTc(OH2)(L∩L)(CO)3] have been synthesized in one step starting from [TcO4]−. Only one bidentate ligand co‐ordinates to the metal centre allowing the co‐ordination of a monodentate ligand which can easily be connected to a biomolecule. Our labeling experiments of peptides bound to a monodentate ligand show that the [2+1] approach is possibly too slow for a radiopharmaceutical application. A similar approach with the biomolecule bound to a bidentate chelator overcomes these disadvantages but retains advantages of the mixed ligand concept.