Carboxy ester hydrolysis promoted by a Zinc(II) 2-[bis(2-aminoethyl)amino]ethanol complex: A new model for indirect activation on the serine nucleophile by Zinc(II) in Zinc enzymes

Xia, J Xu, Y Li, SA Sun, WY Yu, KB Tang, WX

J. Xia et al., Carboxy ester hydrolysis promoted by a Zinc(II) 2-[bis(2-aminoethyl)amino]ethanol complex: A new model for indirect activation on the serine nucleophile by Zinc(II) in Zinc enzymes, INORG CHEM, 40(10), 2001, pp. 2394-2401

39

INGLESE

Article

Inorganic & Nuclear Chemistry

INORGANIC CHEMISTRY

0020-1669 → ACNP

40

10

2001

2394 - 2401

ISI

0020-1669(20010507)40:10<2394:CEHPBA>2.0.ZU;2-3

A complexation study on the new Zn(II) complexes of asymmetric tripodal lig and 2-[bis(2-aminoethyl)amino]ethanol (L) has revealed that the alcoholic O H group of complex ZnL exhibits remarkable acidity with a very low pK(a) va lue 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-r ay diffraction. The Zn(II)-bound alkoxide, as the reactive nucleopile towar d 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 aceta te (NA) hydrolysis, which is almost the same as the corresponding value for the very reactive alcohol-pendent [12]aneN(3)-Zn complex. Present work sho ws for the first time that Zn(II) complexes of the asymmetric tripodal poly amine bearing an ethoxyl pod can also serve as good models of Zn(II)-contai ning enzymes.