Effect of Triamine Ligands (L) on the Acidity of L-Zn-OH2 as a Model Compound of CA and AP

Abstract
The acid dissociation constants of coordinated water of L-Zn-OH2 (L = diethylenetriamine (1),N-(2-aminoethyl)-1,3-propanediamine (2), dipropylenetriamine (3), 1,3,5-triaminocyclohexane (4), and 1,5,9-triazacyclododecane (5)) and the hydrolysis rate constants of diphenyl 4-nitrophenyl phosphate (6) promoted by L-Zn-OH were found to correlate linearly with the enthalpy change (ΔH) for the formation of L-Zn-OH2, which corresponds to the binding energy of Zn-L: the smaller the binding energy is, the stronger the Lewis acidity of zinc ion is and the faster the hydrolysis is.