Comparative Reactivity of Phosphate Ester Hydrolysis Catalyzed by Mononuclear and Hetero-Dinuclear Complexes Containing the Lanthanum Ion (III)

The hydrolysis of bis(p-nitrophenyl phosphate)(BNPP) and p-nitrophenyl phosphate (NPP) were strongly promoted by the mononuclear La^III(N,N-bis(3-carboxyl)-2-hydroxysalicylidene)ethylenediamine] and the hetero-dinuclear Cu^IILa^III(N,N-bis(3-carboxyl)-2-hydroxysalicylidene)ethylenediamine] complexes at 35 °C in 50% aqueous DMSO. The results indicated that the hetero-dinuclear Cu^IILa^III complex exhibited a relatively higher catalytic function on NPP hydrolysis, while the hydrolysis of BNPP was slightly more efficient in the presence of the mononuclear La^III complex than that in the presence of the Cu^IILa^III complex, and this case was discussed by the different spacer requirements for NPP and BNPP hydrolysis. In addition, widely differing pH-rate profiles were obtained: saturated curves for NPP hydrolysis and bell-shaped curves for BNPP hydrolysis, and thus different kinetic treatments were employed to obtain the relative parameters.