Aminopeptidase function of dinuclear zinc(II) complexes of phenol-based dinucleating ligands: effect of p-substituents
摘要:
The aminopeptidase functions of newly obtained dinuclear zinc(II) complexes [Zn,(bonp)(MeCO2)(2)]BPh4 (1) and [Zn-2(bocp)(Me-CO2)(2)]BPh4 (2) were estimated using (L)-leucine-p-nitroanilide as a substrate [H(bonp): 2,6-bis[bis(2-methoxyethyl)aminomethyl]-4-nitrophenol; H(bocp): 4-chloro-2,6-bis[bis(2-methoxyethyl)aminomethyl]phenol]. Both complexes showed aminopeptidase activities, and a second-order rate equation was obtained as v = k [complex] [substrate]. The second-order rate constants k were 5.9(5) x 10(-1) for complex 1, and 2.7(1) x 10(-2) dm(3) mol(-1) s(-1) for complex 2. Compared to the previously reported complex, [Zn-2(bomp)(MeCO2)(2)]BPh4 (3) [H(bomp): 2,6-bis[bis(2-methoxyethyl)aminomethyl]-4-methylphenol], the aminopeptidase activity was improved 250 times by the substitution of the p-methyl group into p-nitro group. The rate constants were found to be ordered as 1 > 2 >3 (250:10:1), and this order is a decreasing order of the electron-withdrawing effect of the p-substituents of the dinucleating ligands 1(-NO2) > 2(-Cl) > 3(-CH3). (C) 2003 Elsevier Science B.V. All rights reserved.