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 (SN2-, SNO2-, SNN2-, SNNO3- and SNNN3-) and different substituents on the sulfur moieties-SR (with R = H, CH3 or C2H5O(CH3)CH). With five of these ligands technetium nitrido complexes have been obtained with high yields (over 95%) using rather harsh conditions (pH = 1, temperature > or = 80 degrees C), whereas for technetium oxo complexes similar high yields were only obtained with two ligands but with mild conditions (pH = 7-8, temperature approximately equal to 50 degrees C). Changing an OH group for an NH2 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.