NMR Studies of the Lanthanide(III) Complexes of 1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetrakis(methanephosphonic acid mono(2‘,2‘,2‘-trifluoroethyl) ester)
| Autor: | Jurriaan Huskens, A. Dean Sherry, Won D. Kim, Garry E. Kiefer |
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| Rok vydání: | 1997 |
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| Zdroj: | Inorganic Chemistry. 36:4128-4134 |
| ISSN: | 1520-510X 0020-1669 |
| Popis: | A new macrocyclic ligand 1,4,7,10,-tetraazacyclododecane-1,4,7,10-tetrakis(methanephosphonic acid mono(2‘,2‘,2‘-trifluoroethyl) ester) (F-DOTPME) has been prepared and some of its metal binding properties examined. The ligand protonation constants (log K1 = 10.5, log K2 = 6.7) and its stability constant with CaII (log KCaL = 8.4) were determined by pH potentiometry. The stability of the LaIII complex could not be determined by potentiometry so it was evaluated in an EDTA competition experiment using 31P NMR to monitor the reaction. The dissociation kinetics of La(F-DOTPME)- was slow, with a kd,obs of only 1.0 × 10-7 s-1. A series of Ln(F-DOTPME)- complexes (LnIII = La, Gd, Dy, Tm, and Yb) were examined by multinuclear NMR. The spectra show that these complexes exist in aqueous solution as a mixture of stereoisomers of nearly equal energy (energy differences of less than 1 kJ/mol). Several resolved 19F resonances in the NMR spectra of the Dy(F-DOTPME)-, Tm(F-DOTPME)-, and Yb(F-DOTPME)- complexes have been ... |
| Databáze: | OpenAIRE |
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