Synthesis and Kinetic Studies of Mono-Schiff Base Manganese(Iii) and Cobalt(Ii) Complexes with Aza-Crown Ether or Morpholino Pendants as Synthetic Hydrolases for P -Nitrophenyl Picolinate

Abstract

Two mono-Schiff base manganese(III) and cobalt(II) complexes with benzo-10-aza-crown ether pendants (MnL¹₂Cl, CoL¹₂), and the analogues with morpholino pendants (MnL²₂Cl, CoL²₂) have been synthesised and employed as models for hydrolase enzymes to promote the hydrolysis of p-nitrophenyl picolinate (PNPP) in buffer solution. A kinetic model of PNPP cleavage catalysed by these complexes is proposed. The effects of the structures of the complexes and reaction temperature on the rate of PNPP hydrolysis have been examined. All four complexes exhibit high catalytic activity and the rate increases with pH. In comparison with the crown-free analogues MnL²₂Cl and CoL²₂, the crowned Schiff base complexes MnL¹₂Cl and CoL¹₂ exhibit higher catalytic activity for promoting PNPP hydrolysis.