Hydrolysis of PNPP catalyzed by Cu (II), Ni (II) schiff base complexes in CTAB micellar solution

The kinetics of hydrolysis of p-nitrophenyl picolinate(PNTP) catalyzed by metallomicelles formed from Cu (H), Ni (H) Schiff base complexes (CuL, NiL) and CTAB micelle were investigated in the pH range of 6.0-9.0 at 30 degrees C. For the Cu (H) Schiff base complex CuL, the apparent rate constants (k(obsd)) of PNPP hydrolysis initially increased with the increasing pH of reaction media, then fell off. For the Ni (H) Schiff base complex NiL, the k(obsd) always increased with the increasing pH. The kinetic and thermodynamic parameters were calculated. The hydrolysis rate of PNPP catalyzed by Cu (H) complex was much larger than that by Ni (H) complex in CTAB micellar solution. The catalytic mechanism of the PNPP hydrolysis was discussed in detail, and the possibly active specie for the catalytic hydrolysis of PNPP was the monohydroxo metal complex.