Publication details
Lanthanide(III) Complexes of 2-[4,7,10-Tris(phosphonomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetic Acid (H7DOA3P): Multinuclear-NMR and Kinetic Studies
| Authors | |
|---|---|
| Year of publication | 2009 |
| Type | Article in Periodical |
| Magazine / Source | Helvetica Chimica Acta |
| MU Faculty or unit | |
| Citation | |
| Web | http://www3.interscience.wiley.com/journal/123189421/abstract |
| Field | Inorganic chemistry |
| Keywords | Macrocycles; Lanthanide complexes; NMR Spectroscopy; Kinetics; Protonation constants |
| Description | The protonation constants of 2-[4,7,10-tris(phosphonomethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetic acid (H7DOA3P) and of the complexes [Ln(DOA3P)]4- (Ln=Ce, Pr, Sm, Eu, and Yb) have been determined by multinuclear NMR spectroscopy in the range pD 2-13.8. Seven out of eleven protonation steps were detected (pK=13.66, 12.11, 7.19, 6.15, 5.77, 2.99, and 1.99), and the values found compare well with the ones for other related ligands. The protonation sequence for H7DOA3P was also tentatively assigned. Three protonation constants (pKMHL, pKMH2L, and pKMH3L) were determined for the lanthanide complexes. The acid-assisted dissociation of [Ln(DOA3P)]4- (Ln=Ce, Eu), in the region cH+=0.05-3.00 mol dm-3 and at different temperatures (25-60 degrees of Celsius), indicated that they have slightly the same kinetic inertness, being the [Eu(H2O)9]3+ aqua ion the final product for europium. The rates of complex formation for [Ln(DOA3P)]4- (Ln=Ce, Eu) were studied by UV/VIS spectroscopy in the pH range 5.6-6.8. |