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

Istvan Lazar, Ravichandran Ramasamy, Erno Brücher, Carlos F G C Geraldes, A. Dean Sherry

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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 31P 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 Ln3+ 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.

Original languageEnglish (US)
Pages (from-to)89-93
Number of pages5
JournalInorganica Chimica Acta
Issue number1
Publication statusPublished - May 1 1992


ASJC Scopus subject areas

  • Biochemistry
  • Inorganic Chemistry
  • Physical and Theoretical Chemistry
  • Materials Chemistry

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