Chain ligand N,N'-bis(2-hydroxylbenzyl)-propylenediamine (H~2L) and its Zn(Ⅱ) complex (ZnL) were synthesized and characterized by elemental analysis, IR and ^1H NMR. By pH titration at 25℃±0.1℃ and I=0.1mol·dm^-^3(KNO~3), protonation constants of the ligand and equilibria constants of Zn(Ⅱ) complexation with the ligand have been determined. Modes of the ligand coordination to Zn(Ⅱ) were discussed, and the dissociation constant for the phenoxyl in complex ZnHL^+ was obtained. The kinetics of p-nitrophenyl acetate (NA) hydrolysis catalyzed by the complexes as carbonic anhydrase models was determined spectrophotometrically at 25℃±0.1℃ and I=0.1mol·dm^-^3 (KNO~3) in 10% (v/v) CH~3CN at pH 5.5～9.0 (50mmol·dm^-^3 buffers), and the second-rate constants for NA hydrolysis were obtained. The experimental results indicate that the dissociation constant pKa value for the phenoxyl in complex ZnHL^+ is 6.83. The pH-k~N~P profile does not exhibit a Sigmoidal curve and the k~N~P reaches a maximum point around neutral pH. The complex ZnHL^+ has very strong catalytic ability around neutral pH following the double- catalysis mechanism, and therefore is a good carbonic anhydrase model.

Key words: CARBONIC ANHYDRASE, PROPANEDIAMINE P, HYDROXYL COMPOUNDS, ZINC COMPLEX, MODELS OF ENZYME, ENZYME SIMULATION, CATALYSIS, REACTION KINETICS, EQUILIBRIUM CONSTANT, NITROPHENOL P