Kinetic study of formation/dissociation of Cu(II) and Zn(II) complexes of cyclen macrocyclic ligand with pendant thiol group
| Authors | |
|---|---|
| Year of publication | 2013 |
| Type | Article in Periodical |
| Magazine / Source | Polyhedron |
| MU Faculty or unit | |
| Citation | |
| Web | http://www.sciencedirect.com/science/article/pii/S0277538713005111# |
| Doi | http://dx.doi.org/10.1016/j.poly.2013.06.052 |
| Field | Inorganic chemistry |
| Keywords | Macrocyclic ligands; Cyclen derivatives; Thiol group; Copper/zinc complexes; Formation/dissociation kinetics; Rate constants; Radiopharmaceuticals |
| Description | The kinetic properties of macrocyclic ligand 2-[1,4,7,10-tetraazacyclododecane-1-yl]-ethanethiol (L1, DOSH) were studied with Cu(II) and Zn(II) metal ions, using conventional molecular absorption spectroscopy in pH regions 2.5-4.7 and 4.3-6.0 for Cu(II) and Zn(II), respectively. The obtained partial rate constants, measured at 25 degrees C and ionic strength I = 0.1 M (KCl), are slightly lower than for parent cyclen (1,4,7,10-tetraazacyclododecane) macrocyclic ligand supporting the hypothesis that the thiol pendant arm is not directly involved in the formation of these metal complexes. The study of the dissociation of the copper(II)-L1 complex in the presence of perchloric acid and at higher temperatures (75-95 degrees C) showed that this complex is more kinetically inert than the copper(II) complex with cyclen, indicating that the presence of the thiol pendant arm plays a key role as protecting group of copper(II) ion. On contrary, the dissociation of zinc(II) complex in presence of copper(II) ion measured at laboratory temperature (25 degrees C) and in 0.1 M-solution of hydrochloric acid is going via the metal-exchange reaction mechanism. Altogether, these findings show that L1 ligand presents favorable kinetic properties for further conjugation with biomolecules, aiming at their use in medicinal chemistry. |
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