Complex formation between Zn2+ ion and 1,3-bis[bis(pyridin-2-ylmethyl)amino]propan-2-ol.

The dinucleating ligand 1,3-bis[bis(pyridin-2-ylmethyl)amino] propan-2-ol (I, LOH) is becoming of increasing interest due to the exceptional phosphate monoester binding and phosphate diester hydrolytic properties of its dizinc(II) complexes in water. Potentiometric pH titrations using a range of Zn:I ratios reveals the formation of mononuclear and dinuclear metal complexes. In fact, when the Zn:I ratio is 1:1 only mononuclear complexes are formed. Previous work reported the formation of only dinuclear species. Thus, the results presented here should be important to interpret correctly and more accurately phosphate ester binding and hydrolysis data. Moreover, based on these findings we suggest that the phosphate binding and hydrolytic properties of mixtures containing Zn(II) ions and I should depend not only on the pH but also on the Zn:I ratio used.