| Popis |
Macrocyclic ligands are used as bifunctional chelating agents in nuclear medicine, e. g. in radioisotope diagnostics (64Cu - Beta+ emitter) or in tumor radiotherapy (67Cu - Beta- emitter). For possible medical applications, it is necessary to know thermodynamic and kinetic properties (rate constants of formation and dissociation) of copper and biometal complexes under experimental conditions similar to body fluids. In this work, the formation and dissociation kinetics of complexes of transitional metal ions with ligands, 1,4,8,11-tetraazacyclotetradecane-1,8-bis(methylphosphonic) acid (dipon, H4L1) and 4,11-dimethyl-1,4,8,11-tetraazacyclotetradecane-1,8-bis(methylphosphonic) acid (dimeMe2dipon, H4L2)was studied. The ligands form stable complexes with transitional metal ions Cu2+, Zn2+, Cd2+, Pb2+, Ca2+, Mg2+, Ni2+, Co2+. Formation (kf) and dissociation (kd) constants of Cu2+, Zn2+ and Cd2+ complexes with ligands dipon and dimeMe2dipon were measured under experimental conditions (t = 25oC, I = 0,1 mol.l-1). The formation and dissociation of metal complex of both ligands were explained and reaction mechanisms were postulated. The highest stability (kinetic as well as thermodynamic) is demonstrated by both ligands for copper(II), while the complex is already formed in solutions with pH lower than 2. The formation rate of copper complex of both ligands complex is 1000 times higher than complexes with the other studied ions. The dissociation of this complex takes place at lower pH than complexes with the other studied ions.
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