Spectroscopic Characterization of New Eu(III)/DOTA Analogue Complexes as potential MRI Agents
| Authors | |
|---|---|
| Year of publication | 2003 |
| Type | Article in Proceedings |
| Conference | Abstract Book of Conference "TOWARDS MOLECULAR ELECTRONICS" (Central European Conference on Advanced Materials and Nanotechnology), Srem, Poland, June 23-28, 2003. |
| MU Faculty or unit | |
| Citation | |
| Field | Analytic chemistry |
| Keywords | MRI; macrocyclic ligands; europium(III); lumininiscence study; luminiscent probes |
| Description | Ln(III) complexes of DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate) and their analogues are used for their high thermodynamic stability, kinetic inertness and other properties as MRI or luminescent probes in medicine. New analogues of DOTA were prepared by substitution of one acetic group by pendant groups containing phosphonic group. The formation kinetics between Eu(III) and recently synthesized ligands were studied under experimental conditions (t = 25 oC, I = 0.1 mol.l-1, pH = 4-6) by means of UV/VIS absorption spectroscopy and two steps were observed: Eu3+ + HxL <=> (x-y)H+ + Eu(HyL) --> Eu(L) + yH+ The first step - the coordination of Eu(III) ion by pendant groups is very fast. In the second step, the transformation of an intermediate to the final complex in which Eu(III) ion is coordinated by four pendant groups and four nitrogen donor atoms of the cyclen ring, takes place. This step is very slow and it is proportional to OH- ion concentration. The estimates of protonation constants of the intermediates and rate constants of the second step were determined. A luminescence life time studies revealed that the number of water molecules coordinated to the Eu(III) ion in Eu(L) complexes at pH = 7.4 is about one (q=1) what proves that the Eu(III) ion is also bound by phosphonic group. |
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