Pentadentate chiral amine-phenol ligands: synthesis and radiochemical studies with 99mTc

Two pentadentate chiral amine-phenol ligands were synthesized by condensing 2-hydroxyacetophenone with diethylenetriamine or 3,3′-diamino-N-methyldipropylamine and reducing the resultant Schiff base ligands with NaBH4. The ligands were characterized by 1H and 13C NMR spectroscopy. The amine-phenol ligands form a mixture of d, l and meso isomers and complexation studies with Tc (99m and/or 99) were done without separation of the isomers. Radiochemical studies of the amine-phenol ligands with 99mTc and 99Tc were carried out at technetium concentrations varying from 0.1 to 100 μM. Complex yields were estimated by TLC, paper electrophoresis and solvent extraction studies. 99mTc complexes are readily formed in yields >95% in NCA 99mTcO4− studies, and the resultant complexes were found to be neutral, lipophilic and stable. The present studies suggest that the pentadentate chiral ligands may be suitable candidates for developing new Tc chelates as radiopharmaceuticals or as bifunctional chelating agents for labeling biomolecules.