Metallomicellar Catalysis: Catalytic Cleavage of p-Nitrophenyl Picolinate by Cu2+ Complex of 4-Chloride-2,6-bis(N-hydroxyethylaminomethyl)-benzophenol in Micellar Solution

Two cobalt(II) complexes of the Schiff base with morpholino or aza-crown ether pendants, CoL 1 and CoL 2 , as mimic hydrolytic metalloenzyme, were used in catalytic hydrolysis of carboxylic ester (PNPP). The analysis of specific absorption spectra of the hydrolytic reaction systems indicates that key intermediates, made up of PNPP and Co(II) complexes, have been formed in reaction processes of the PNPP catalytic hydrolysis. The mechanism of PNPP catalytic hydrolysis has been proposed based on the analytic result of specific absorption spectrum. A kinetic mathematical model, applied to the calculation of the kinetic parameter of PNPP catalytic hydrolysis, has been established based on the mechanism proposed. The acid effect of buffer solution, structural effect of the complexes, and effect of temperature on the rate of PNPP hydrolysis catalyzed by the complexes have been also discussed.

Studies on PNPP Hydrolysis Catalyzed by Schiff Base Cobalt(II) Complexes

Xiao

et al. 2006

Catalytic Kinetics of the Schiff Base Metal Complexes Bearing Side Chain of Cyclic morpholine in Carboxylic Ester Hydrolysis

Zhang¹,

Li²,

Ou³

et al. 2007

It has been reported that two Schiff base transition metal complexes bearing the side chain of the morpholine ring were synthesized and characterized, and two complexes with the same base agent but different metal ions were used as a simulant hydrolase in the catalytic hydrolysis of p-nitrophenyl picolinate in this paper. The mechanism of PNPP catalytic hydrolysis is proposed and supported by the results of the spectral analysis and the kinetic calculation. A kinetic mathematical model, applied to the calculation of the kinetic and thermodynamics parameters of PNPP catalytic hydrolysis, has been established on the foundation of the mechanism proposed. The result of the study shows that the two complexes have a good catalytic activity in PNPP catalytic hydrolysis, and the rate of the PNPP catalytic hydrolysis was increased with the increase of the pH values in the buffer solution and affected by the polarization effect of metal ion of the complexes.

Studies on PNPP Hydrolysis Catalyzed by Schiff Base Cobalt(II) Complexes Containing Benzoaza‐15‐crown‐5

Wang

et al. 2007

Three novel Schiff base cobalt(II) complexes containing benzoaza-15-crown-5, CoL 1 , CoL 2 and CoL 3 were synthesized and characterized, and these complexes were used in catalytic hydrolysis of carboxylic ester (PNPP, p-nitrophenyl picolinate) as mimic hydrolytic metalloenzyme. The analysis of specific absorption spectra of the hydrolytic reaction systems indicated that the catalytic hydrolysis involved the key intermediates formed by PNPP with cobalt(II) complexes. The CoL 3 bearing the electron withdrawing group shows better catalytic activity due to its stabilization effect on active species MLS -. The catalytic mechanism of PNPP hydrolysis was also proposed. The kinetic parameter of PNPP catalytic hydrolysis has been calculated and the activation energy for the catalytic hydrolysis is 43.69, 39.76 and 35.44 kJ•mol -1 , respectively.