Abstract
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 K ML values is greater for soft than for hard metal ions, compared to corresponding values for 1,4,7-triazacyclononane-1,4,7-triacetate.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
