STABILITY-CONSTANTS OF METAL-COMPLEXES OF MACROCYCLIC LIGANDS WITH PENDANT DONOR GROUPS

In our studies of the stability constants of metal complexes, we have investigated a number of macrocyclic ligands with pendant donor groups . The ligands are characterized by the fact that they have nitrogen do nors in the macrocyclic ring and oxygen or sulfur donors in the pendan t arms. These ligands represent seven different macrocycles, and by va rying the pendant donor groups, ten different Ligands are indicated. T he affinities of these ligands for fifteen metal ions will be describe d. The Fe(III) complex of triazanonane with o-hydroxypyridyl or o-hydr oxybenzyl pendant donor groups are the most stable ferric complexes ev er reported. The In(III) complex of triazacyclononane with pendant mer capto-ethyl donor groups, is exceptionally stable. Also, the Ca(II) co mplex of DOTA probably has the highest stability of any calcium(II) co mplex. These, and other comparisons will be made on the basis of the t hermodynamic stability constant data for the ligands described.