Kinetic Study on p-Nitrophenyl Picolinate Hydrolysis Catalyzed by Metallomicelle

Abstract

Abstract Two transition metal ion macrocyclic complexes, NiR and CuR (R: 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraaza-cyclotetradecane perchloric acid), were synthesized and characterized. Metallomicelles made up of nickel (II) and copper (II) complexes with surfactant n -lauroyl sarcosinate were used as a mimetic hydrolytic metalloenzyme for catalytic hydrolysis of p -nitrophenyl picolinate (PNPP). The specific absorption spectra of the hydrolytic reaction systems indicated that the key intermediates made up of PNPP and Ni(II) or Cu(II) complex were formed during the reaction process. Based on the specific absorption spectra, the mechanism of PNPP catalytic hydrolysis was proposed, and a kinetic mathematical model was established. The results showed that the two metallomicelles exhibit high catalytic activity for the hydrolysis of PNPP. The catalytic hydrolysis of PNPP is an intramolecular nucleophilic substitution reaction, so the rate of the catalytic reaction is higher than that of spontaneous hydrolysis. The catalytic mechanism proposed is supported by the results of spectral analysis and the kinetic calculation. The structure of NiR and CuR is similar so that the difference in the catalytic activity between the two metallomicelles is less.