An europium(III) hydrolytic catalyst favoring anionic phosphate esters over phosphate triester

A Cryptate (221) having a short alcohol pendant (2) was metallated with eur opium(III) in anhydrous condition, and its hydrolytic activity for phosphat e esters at neutral pH was examined. While the activity for the phosphate d iester and monoester is comparable to that of the parent metal complex [1Eu ](3+), its hydrolytic activity towards a phosphate triester is significantl y suppressed. Potentiometric titration and luminescence spectroscopic studi es for the equilibrium behavior of the complex in solution suggest that a d imer formation through the metal hydroxides as well as the pendant alcohol is likely to happen. The low hydrolytic activity for the triester seems to be associated with the dimer formation.