Influence of trans-1,2-diaminocyclohexane structure and mixed carboxylic/phosphonic group combinations on samarium-153 chelation capacity and stability.

A simple procedure was developed to compare chelating agents for (153)Sm complexes as a preliminary step to synthesise bifunctional analogues. Several variables affecting the efficiency of complex stability were investigated, such as the pre-organisation concept, cavity size, and the nature of coordination sites. Four semi-rigid agents incorporating carboxylic and/or phosphonic groupings fixed at trans-1,2-diaminocyclohexane were evaluated for their (153)Sm chelation properties, and competition studies were performed. Data on the stability of the best chelating agent compound 3: trans-cyclohexane-1,2-bis(aminomethylphosphonic)-N,N'-bis(ethyl-2-iminodiacetic acid) in human serum are presented.