Kinetic studies on hydrolysis of p-nitrophenol picolinate mediated by mono-Schiff base Mn(III) complexes as synthetic hydrolase

Three novel mono-Schiff base manganese(III) complexes (metal: ligand = 1: 2) with benzoaza-15-crown-5 or morpholine pendant groups, were shown to promote the hydrolysis of p-nitrophenol picolinate (PNPP) under a series of experimental conditions. A mechanism for these catalysts is proposed in which the H2O molecule that hydrolyses the PNPP is deprotonated by the synergistic effect which results from central Mn(III) ion and oxygen atom located in the benzoaza-15-crown-5 or morpholine ring. The related kinetic model has been set up. The effects of structural differences of the listed complexes on the hydrolysis of PNPP have been discussed. The experimental results imply that the steric hindrance of side pendant groups is a primary factor for PNPP hydrolysis.