SYNTHESIS AND CHARACTERIZATION OF A NOVEL MACROCYCLIC LIGAND CONTAINING 9 DONOR ATOMS

The synthesis of a novel macrocyclic ligand containing nine potential coordination sites (six nitrogens and three oxygens) formed by a triaz acyclododecane ring trisubstituted with -CH2CH2-N(CH(2)Ph)-CH2COOH gro ups is reported. The protonation scheme of this ligand has been elucid ated by measuring the proton NMR shifts of the various methylenic reso nances upon changing the pH of the solution. This ligand affords stabl e metal complexes with Cd2+ ion, whose H-1- and C-13-NMR spectra sugge st a remarkable kinetic inertia and stereochemical rigidity.