Informace o publikaci

Tris(phosphonomethyl)cyclen Derivatives: Thermodynamic Stability, Kinetics, Solution Structure, and Relaxivity of Ln(3+) Complexes

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LIMA Luis M.P. DELGADO Rita HERMANN Petr ŠEVČÍK Radek LUBAL Přemysl CARVALHO Henrique F. MARTINS André F. TÓTH Éva GERALDES Carlos F.G.C.

Rok publikování 2012
Druh Článek v odborném periodiku
Časopis / Zdroj Eur. J. Inorg. Chem.
Fakulta / Pracoviště MU

Středoevropský technologický institut

Citace
www http://onlinelibrary.wiley.com/doi/10.1002/ejic.201101335/abstract
Doi http://dx.doi.org/10.1002/ejic.201101335
Obor Anorganická chemie
Klíčová slova macrocyclic ligands; lanthanide complexes; thermodynamics; kinetics; relaxivity
Popis The lanthanide (Ln3+) complexes of three cyclen-based ligands containing three methylphosphonate pendant arms were studied, the ligands being 1,4,7,10-tetraazacyclododecane-1,4,7-triyltris(methylphosphonic acid) (H6do3p), 3-[4,7,10-tris(phosphonomethyl)-1,4,7,10-tetraazacyclododec-1-yl]propanoic acid (H7do3p1pr), and 10-(3-hydroxypropyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyltris(methylphosphonic acid) (H6do3p1ol). The three macrocyclic ligands form complexes of very high thermodynamic stability with all studied Ln3+ ions. Kinetic studies showed that the acid-assisted dissociation of Ce3+ complexes of these ligands is much faster than for the complex of the related ligand H8dotp [1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayltetrakis(methylphosphonic acid)]. The number of water molecules coordinated to the Eu3+ and Gd3+ complexes was estimated to be < 1 for the do3p1ol ligand but ca. 1 for the other two ligands, as obtained by time-resolved luminescence spectroscopy and by 1H and 17O relaxometric measurements. The NMR spectroscopic data indicate the existence of a considerable contribution from second-sphere water molecules to the relaxivity of all the Gd3+ complexes studied. The 1H and 31P NMR spectra of the Eu3+, Yb3+ and Lu3+ complexes showed that the propionate arm in the [Ln(do3p1pr)]4 complexes and the propanol arm in the [Ln(do3p1ol)]3 complexes are not bound to the Ln3+ ion. The [Ln(do3p)]3 and [Ln(do3p1pr)]4 complexes have a clear preference for the TSAP (twisted square antiprismatic) isomer, while both SAP (square antiprismatic) and TSAP isomers are present in solutions of the [Ln(do3p1ol)]3 complexes.
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