Hydrolysis of p-Nitrophenyl Picolinate Catalyzed by Copper(II) and Zinc(II) Binuclear Complexes Coordinating Tripeptide in Micellar Solution

Abstract

The kinetic model of binuclear metal complex catalysis involving a ternary complex in CTAB micellar solution is proposed in this paper. The catalyzed hydrolysis of p-nitrophenyl picolinate catalyzed by Cu(II) and Zn(II) coordinating tripeptide was studied kinetically by observing the rates of the release of p-nitrophenol in the buffered micellar solution at 25°C and different pH values. The proposed kinetic model is confirmed by experimental results which indicate that the 1 : 2 complexes of the ligand to metal ion are the active species in the reaction and the complexes catalyze efficiently the hydrolysis of PNPP, especially Cu(II) complex. The pK_a of hydroxyl group of the ternary complex was determined to be 8.24, and the maximum rate constant which shows that the nucleophilic reactivity of complexes was determined to be 0.0262 s⁻¹ for Cu(II) complex. The catalytic mechanism of reaction is discussed in bifunctional mechanism.

Keywords:

• Binuclear metal complexes
• Catalytic kinetic
• Hydrolysis of p-nitrophenyl picolinate
• Metallomicelle
• Tripeptide

ACKNOWLEDGMENT

This work was supported by the National Natural Science Foundation of China (Grant: 29873031).