The macrocycles 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane-7,16-bis(malonate) (oddm), -7-malonate (odmm) and -7,16-bis(α-methylacetate) (oddp) have been synthesized. Their protonation constants and the stability constants of their complexes ML with Mg2+, Ca2+, Sr2+, Ba2+, Mn2+, Zn2+, Cd2+ and Pb2+ have been determined by pH-potentiometry at a 1:1 metal-to ligand ratio. The macrocycle oddm possesses high selectivity for the large metal ions. The complex [Sr(oddm)]2- is two orders of magnitude more stable than [Ca(oddm)]2- and the stability constant of [Pb(oddm)]2- is six orders of magnitude larger than that of the corresponding zinc complex. The complexes of oddm with large metal ions (Sr2+ and Ba2+) possess rigid structures, while the average lifetimes of the metal-donor bonds are relatively large, and this is indicated by the appearance of multiplet signals in the 1H NMR spectra.
|Original language||English (US)|
|Number of pages||5|
|Journal||Journal of the Chemical Society, Dalton Transactions|
|State||Published - Dec 1 1995|
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