A complexation study on the new Zn(II) complexes of asymmetric tripodal ligand 2-[bis(2-aminoethyl)amino]ethanol (L) has revealed that the alcoholic OH group of complex ZnL exhibits remarkable acidity with a very low pK(a) value of 7.7 at 25 degreesC. Both the monomeric complex [ZnH-0.25L(H2O)](ClO4)(1.75) (I) and the dimeric alkoxide-coordinating complex [Zn-2(H-L-1)(2)](ClO4)(2) (II) were synthesized, and their structures were determined by X-ray diffraction. The Zn(II)-bound alkoxide, as the reactive nucleopile toward the hydrolysis of eaters, has shown a second-order rate constant of 0.13 +/- 0.01 M-1 s(-1) in 10% (v/v) CH3CN at 25 degreesC in 4-nitrophenyl acetate (NA) hydrolysis, which is almost the same as the corresponding value for the very reactive alcohol-pendent [12]aneN(3)-Zn complex. Present work shows for the first time that Zn(II) complexes of the asymmetric tripodal polyamine bearing an ethoxyl pod can also serve as good models of Zn(II)-containing enzymes.