Synthesis, potentiometric and1H NMR study of protonation and complex formation of 1,4,7-triazacyclononane-1,4-diacetate

István Lázár, Róbert Király, Zsuzsanna Takács

Research output: Contribution to journalArticle

5 Citations (Scopus)


Protonation constants and the protonation scheme of 1,4,7-triazacyclononone-1,4-diacetate (NO2A) have been determined by pH potentiometry and 1H NMR techniques; shielding constants valid for the entire pH range have been calculated. It has been pointed out that the most basic site in the molecule is the unsubstituted secondary amino group. The first two protonation steps belong to ring nitrogens, the third and fourth ones to the carboxylates; the last nitrogen is protonated in very acidic solutions only. Stability constants of complexes of NO2A with selected divalent and trivalent metal ions were determined; with them no indication of kinetic inertness was found. In NO2A complexes the relative contribution of the triazacyclononane ring to the log KML values is greater for soft than for hard metal ions, compared to corresponding values for 1,4,7-triazacyclononane-1,4,7-triacetate.

Original languageEnglish
Pages (from-to)293-304
Number of pages12
JournalJournal of Coordination Chemistry
Issue number3
Publication statusPublished - Jan 1 2000


  • 1,4,7-triazacyclononane
  • Complexes
  • Macrocycles
  • NMR
  • Potentiometry
  • Protonation
  • Shielding

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Materials Chemistry

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