Synthesis, potentiometry, and NMR studies of two new 1,7-disubstituted tetraazacyclododecanes and their complexes formed with lanthanide, alkaline earth metal, Mn(2+), and Zn(2+) ions

Both of the two new 1,7-disubstituted-1,4,7,10-tetraazacyclododecane ligands DO2P and DO2PME form 1:1 M:L complexes with lanthanide, alkaline, earth metal, Mn(2+) and Zn(2+) ions. According to 17O shifts, 1H relaxation rates and 31P nuclear magnetic resonance data, the nonprotonated Ln(3+) complexes are in an 'in-cage' position in LnHDO2P and are octacoordinate, with six ligand donors and two inner-sphere coordinated water molecules. In the diprotonated complexes, however, the Ln(3+) cation shifts to an 'out-of-cage' position.