KINETIC STUDIES OF COMPLEXATION AND DECOMPLEXATION OF BIS(PHOSPHONIC ACID) CYCLAM DERIVATIVES WITH COPPER(II) ION
| Authors | |
|---|---|
| Year of publication | 2004 |
| Type | Article in Proceedings |
| Conference | Book of Abstracts of Inorganic Reaction Mechanisms Meeting 2003, January 8-10, 2004, Athens, Greece |
| MU Faculty or unit | |
| Citation | |
| Field | Analytic chemistry |
| Keywords | BIS(PHOSPHONIC ACID) CYCLAM DERIVATIVES; copper(II) complexes; thermodynamics; kinetics |
| Description | Complexes of Cu(II) with macrocyclic ligands are utilized as bifunctional chelating agents in nuclear medicine, e.g. in radioisotope diagnostics (64Cu) or in tumor radiotherapy (67Cu). There is necessity to know thermodynamic and kinetic properties (formation and dissociation rate constants) of copper and other biometal ion complexes under experimental conditions similar to body fluids for possible medical application in vivo. In this work, the formation kinetics of copper(II) complexes of macrocyclic ligands with phosphonic acid pendant arms was studied (dipon, L1, Me2dipon, L2, dipon-diester, L3) (t = 25 oC, I = 0.1 M). The reactivity decreases in order L1 > L2 > L3. The copper(II) complex of L1 ligand can be found in two isomeric forms. They differ in the number of bound donor atoms and cyclam skeleton arrangement. The mechanism of isomerisation reaction was studied in different media (aqueous ammonia, water) by means of different experimental techniques and catalysis of reaction by ammonia was observed. The dissociation kinetics of copper(II) complexes of L1 and L2 macrocyclic ligands was investigated under extreme experimental conditions (t = 25-65 oC, I = 5 M (Na,H)ClO4). The acid-assisted dissociation of complexes is faster for [Cu(H2L2)] than for [Cu(H2L1)] compounds. In case [Cu(H2L1)], both isomeric species demonstrate a high kinetic inertness in presence of 5 M perchloric acid (t = 25 oC, Tau1/2 = 20 min and 6.7 months for penta- and hexacoordinated isomers, respectively). |
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