| Abstract
| - Three stable dinuclear zinc(II) complexes, [Zn2L1(μ-NO3)(NO3)2] and [Zn2L1(μ-OMe)(NO3)2], whereL1 is 2,6-bis{[N-(2-dimethylaminoethyl)-N-methyl]aminomethyl}-4-methylphenolate, and [Zn2L2(NO3)3], whereL2 is 2-{[N-(2-dimethylaminoethyl)-N-methyl]aminomethyl}-4-bromo-6-{[N‘-2-(2‘-pyridyl)ethyl]aminomethyl}phenolate, were synthesized and characterized in the solid state and in aqueous solution. These complexescatalyze the hydrolysis of penicillin G and nitrocefin, serving as functional synthetic analogues of the metallo-β-lactamases, bacterial enzymes responsible for antibiotic resistance. The mechanism of the hydrolysis wasstudied in detail for the catalyst precursor [Zn2L1(μ-NO3)(NO3)2], which converts into [Zn2L1(μ-OH)(NO3)n(sol)2-n](2-n)+ in the presence of water. The complex [Zn2L1(μ-OH)(NO3)2] (n = 2) was characterized in thesolid state. Initial coordination of the substrate carboxylate group is followed by the rate-limiting nucleophilicattack of the bridging hydroxide at the β-lactam carbonyl group in aqueous solution. The product is formedupon fast protonation of the intermediate. Mononuclear complexes Zn(cyclen)(NO3)2 and Zn(bpta)(NO3)2 areas reactive in the β-lactam hydrolysis as the dinuclear complexes. Consequently, the second zinc ion is notrequired for catalytic activity.
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