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Title: Potentiometry and NMR studies of 1,5,9-triazacyclododecane-N,N',N''-triacetic acid and its metal ion complexes
Authors: Cortes, S. 
Brucher, E. 
Geraldes, C. F. G. C. 
Sherry, A. D. 
Issue Date: Jan-1990
Publisher: American Chemical Society
Citation: Inorganic Chemistry. 29:1 (1990) 5-9
Abstract: A new chelating macrocycle, 1,5,9-triazacyclododecane-N,N’,N’’-triacetiacc id (DOTRA), has been synthesized, and its complexes with Zn2’, Cd2+, Ca2+, Mg2+, and Mn2+ have been examined by potentiometry and NMR spectroscopy. The first protonation constant of the free ligand (log K, = 12.8) was determined spectrophotometrically, while the remaining were evaluated from potentiometric data (log K2 = 7.55, log K, = 3.65, log K4 = 2.1). DOTRA forms complexes with Mn2+, Mg2’, and Ca2+ rather slowly but reacts much more rapidly with Zn2+ and Cd2+. As reported previously for the nine-membered-ring triaza analogue NOTA, DOTRA also forms a more stable complex with Mg2+ than with Ca2+ (log K,, = 7.1 versus 6.0). High-resolution NMR spectra of the Zn2+, Cd2+, and Mgzt complexes (log K,, = 19.0, 15.7, and 7.1, respectively) indicate the three six-membered chelate rings are symmetrical and quite rigid in aqueous solution, as evidenced by nonequivalence of all six chelate ring protons.
ISSN: 0020-1669
DOI: 10.1021/ic00326a003
Rights: openAccess
Appears in Collections:FCTUC Química - Artigos em Revistas Internacionais

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