Asymmetric mono- and dinuclear Ga-III and Zn-II complexes as models for purple acid phosphatases

摘要

Derivatives of the known dinucleating ligands HL1 (2,6-bis{[bis(pyridin-2-ylmethyl)amino]methyl}-4-methylphenol) and H2L2 (2-([bis(pyridin-2-ylmethyl)amino]methyl}-6-([(2-hydroxybenzyl)(pyridine-2-ylmethyl)amino]methyl}-4-methylphenol) with two pivaloylamido hydrogen bond donor substituents, H3L3 and H3L5, have been prepared. The mono-, homo- and heterodinuclear Zn-II and Ga-III complexes of these ligands have been prepared and characterized. The solution equilibria are discussed on the basis of extensive NMR spectroscopic, mass spectrometric and pH-dependent UV-vis spectroscopic titrations. The phosphoester hydrolysis activity of the complexes has been studied as a function of pH and substrate concentration and analyzed using Michaelis-Menten kinetics. It emerges that the mixed metal (mixed valent) complex of the ligand with an asymmetric disposition of the hydrogen bonding substituents (H3L3) is a functional model for the mixed valent, dinuclear metallohydrolase purple add phosphatase. This complex combines the essential structural features of the active site of PAP and is the first heterodinuclear model complex mimicking the essential function of PAPs, i.e. the hydrolysis of phosphomonoesters. (C) 2015 Elsevier Inc All rights reserved.