Thermodynamic and Kinetic Studies of Lanthanide(III) Complexes with H5do3ap (1,4,7,10-Tetraazacyclododecane-1,4,7-triacetic-10-(methylphosphonic Acid)), a Monophosphonate Analogue of H4dota

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Title:Thermodynamic and Kinetic Studies of Lanthanide(III) Complexes with H5do3ap (1,4,7,10-Tetraazacyclododecane-1,4,7-triacetic-10-(methylphosphonic Acid)), a Monophosphonate Analogue of H4dota
Creators:
Táborský, Petr
Lubal, Přemysl
Havel, Josef
Kotek, Jan
Hermann, Petr
Lukeš, Ivan
Journal or Publication Title:
Collection of Czechoslovak Chemical Communications, 70, 11, pp. 1909-1942
Uncontrolled Keywords:Potentiometry, Lanthanide cations, Kinetics, Crystal structure determination, Azacrown compounds, Cerium, Macrocyclic ligand, Cyclen derivative, Thermodynamics, Phosphonate complexes, Gadolinium, DOTA, Tetraazacyclododecane

Abstract

Solution properties of complexes of a new H<sub>4</sub>dota-like ligand containing three acetate and one methylphosphonate pendant arms (H<sub>5</sub>do3ap, H<sub>5</sub>L) were studied. The ligand exhibits a high last dissociation constant (p<i>K</i><sub>A</sub> = 13.83) as a consequence of the presence of phosphonate moiety. In solution, successive attachment of protons leads to several reorganizations of protonation sites and the neutral zwitterionic species H<sub>5</sub>do3ap has the same solution structure as in the solid state, where the nitrogen atom binding methylphosphonate and the opposite nitrogen atoms are protonated. Stability constants with Na<sup>+</sup> and trivalent lanthanide ions (La<sup>3+</sup>, Ce<sup>3+</sup>, Eu<sup>3+</sup>, Gd<sup>3+</sup>, Lu<sup>3+</sup>) and Y<sup>3+</sup> have been determined. The constants are comparable or higher than those of H<sub>4</sub>dota due to the higher overall basicity of H<sub>5</sub>do3ap. Formation of the stable protonated complexes, as well as complexes with the L:M&nbsp;= 1:2 stoichiometry, was proved. Formation and decomplexation kinetics of the Ce<sup>3+</sup> and Gd<sup>3+</sup> complexes were investigated. The mechanism of formation of the H<sub>5</sub>do3ap complexes is similar to that observed for H<sub>4</sub>dota complexes and the complex species with mono- or diprotonated ligand on the cyclen ring are considered as the reaction intermediates. Acid-assisted decomplexation of H<sub>5</sub>do3ap complexes is faster in comparison with those of H<sub>4</sub>dota. This is caused by higher basicity of the phosphonate pendant arm and the ring nitrogen atoms, which facilitates the proton transfer from the bulk solution to the nitrogen atoms of cyclen ring. <p>

Title:Thermodynamic and Kinetic Studies of Lanthanide(III) Complexes with H5do3ap (1,4,7,10-Tetraazacyclododecane-1,4,7-triacetic-10-(methylphosphonic Acid)), a Monophosphonate Analogue of H4dota
Creators:
Táborský, Petr
Lubal, Přemysl
Havel, Josef
Kotek, Jan
Hermann, Petr
Lukeš, Ivan
Uncontrolled Keywords:Potentiometry, Lanthanide cations, Kinetics, Crystal structure determination, Azacrown compounds, Cerium, Macrocyclic ligand, Cyclen derivative, Thermodynamics, Phosphonate complexes, Gadolinium, DOTA, Tetraazacyclododecane
Divisions:Life and Chemical Sciences > Institute of Organic Chemistry and Biochemistry > Collection of Czechoslovak Chemical Communications
Journal or Publication Title:Collection of Czechoslovak Chemical Communications
Volume:70
Number:11
Page Range:pp. 1909-1942
ISSN:0010-0765
E-ISSN:1212-6950
Publisher:Institute of Organic Chemistry and Biochemistry
Related URLs:
URLURL Type
http://dx.doi.org/10.1135/cccc20051909UNSPECIFIED
ID Code:2447
Item Type:Article
Deposited On:06 Feb 2009 17:18
Last Modified:06 Feb 2009 16:18

Citation

Táborský, Petr; Lubal, Přemysl; Havel, Josef; Kotek, Jan; Hermann, Petr; Lukeš, Ivan (2005) Thermodynamic and Kinetic Studies of Lanthanide(III) Complexes with H5do3ap (1,4,7,10-Tetraazacyclododecane-1,4,7-triacetic-10-(methylphosphonic Acid)), a Monophosphonate Analogue of H4dota. Collection of Czechoslovak Chemical Communications, 70 (11). pp. 1909-1942. ISSN 0010-0765

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