Technetium labeling of bi, tri and tetradentate ligands derived from 2-aminocyclopentene-1-dithiocarboxylic acid: Characterization and biodistribution of their oxo and nitrido 99mtechnetium complexes

We have synthesized and characterized seven ligands derived from 2-aminocyclopentene-1-dithiocarboxylic acid with different donor sets (SN 2−, SNO 2−, SNN 2−, SNNO 3− and SNNN 3−) and different substituents on the sulfur moieties -SR (with R = H, CH 3 or C 2H 5O(CH 3)CH). With five of these ligands technetium nitrido complexes have been obtained with high yields (over 95%) using rather harsh conditions (pH ≈ 1, temperature ≥ 80 °C), whereas for technetium oxo complexes similar high yields were only obtained with two ligands but with mild conditions (pH = 7–8, temperature ≈ 50 °C). Changing an OH group for an NH 2 has a drastic effect upon labeling yields. The possibility of complexing ligands as either oxo (TcO) 3+ or nitrido (TcN) 2+ derivatives increases the number of available labeled agents with different overall change and consequently with different biological behavior.