TY - JOUR
T1 - NMR and potentiometric studies of 1,4,7-triazacyclononane-N,N′,N″-tris(methylenephosphonate monoethylester) and its complexes with metal ions
AU - Lazar, Istvan
AU - Ramasamy, Ravichandran
AU - Brücher, Erno
AU - Geraldes, Carlos F G C
AU - Sherry, A. Dean
N1 - Funding Information:
We thank the Meadows Foundation and the Robert A. Welch Foundation (At-584) for financial support.
PY - 1992/5/1
Y1 - 1992/5/1
N2 - 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.
AB - 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.
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U2 - 10.1016/S0020-1693(00)83854-2
DO - 10.1016/S0020-1693(00)83854-2
M3 - Article
AN - SCOPUS:0008733615
SN - 0020-1693
VL - 195
SP - 89
EP - 93
JO - Inorganica Chimica Acta
JF - Inorganica Chimica Acta
IS - 1
ER -