Studies on the hydrolysis of P-nitrophenyl acetate catalyzed by zinc(II) complexes with an S2N2 binding set

A series of neutral four-coordinated zinc(II) complexes with S2N2 binding s et were synthesized and found to have remarkable catalytic activities towar ds the hydrolysis of p-nitrophenyl acetate (NA). The kinetics in aqueous Tr is-HCl [Tris = tris(hydroxymethyl)aminomethane] buffer solution (pH = 7.50) containing 40% (v/v) acetonitrile at 25 +/- 0.1 degreesC, I = 0.1 M (adjus ted with NaCl) were studied and the second order rate constants k(c) (M(-1) s(-1)) were obtained. The results revealed that the catalytic activities of these complexes towards the hydrolysis of NA were close to those of Zn(II) complexes reported as carbonic anhydrase (CA) model complexes.