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NMR and potentiometric studies of 1,4,7-triazacyclononane-N,N′,N″-tris(methylenephosphonate monoethylester) and its complexes with metal ions

Authors :
István Lázár
Ravichandran Ramasamy
A. Dean Sherry
Carlos F. G. C. Geraldes
Ernö Brücher
Source :
Scopus-Elsevier, CIÊNCIAVITAE
Publication Year :
1992
Publisher :
Elsevier BV, 1992.

Abstract

1,4,7-Triazacyclononane- N , N ′, N ″-tris(methylene-phosphonate monoethylester) (NOTPME) and its complexes with the trivalent lanthanide cations and divalent calcium, magnesium, zinc and cadmium have been examined by potentiometry and NMR. The 31 P NMR spectra of the lanthanide-NOTPME complexes show single resonances characteristic of symmetrical chelated species at low concentrations (below 0.1 mM) but multiple resonances at higher concentrations. This tendency of the neutral complexes to form unsymmetrical, perhaps oligomeric, species is dependent upon the size of the Ln 3+ and the solution pH. The alkaline earth and divalent transition metal cation complexes do not show this same behavior. The stability constants of the Ln(NOTPME) complexes were found to be considerably smaller than their respective Ln(NOTA) complexes.

Details

ISSN :
00201693
Volume :
195
Database :
OpenAIRE
Journal :
Inorganica Chimica Acta
Accession number :
edsair.doi.dedup.....536c8cedc10a5860cf61057bcca46f4a
Full Text :
https://doi.org/10.1016/s0020-1693(00)83854-2