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    Unsymmetrical FeIIICoII and GaIIICoII Complexes as Chemical Hydrolases: Biomimetic Models for Purple Acid Phosphatases (PAPs)


    Xavier, Fernando R., Neves, Ademir, Casellato, Annelise, Peralta, Rosaly A., Bortoluzzi, Adailton J., Szpoganicz, Bruno, Severino, Patricia C., Terenzi, Hernan, Tomkowicz, Zbigniew , Haase, Wolfgang, Ozarowski, Andrew, Krzystek, Jerzy , Telser, Joshua, Schenk, Gerhard and Gahan, Lawrence R. (2009) Unsymmetrical FeIIICoII and GaIIICoII Complexes as Chemical Hydrolases: Biomimetic Models for Purple Acid Phosphatases (PAPs). Inorganic Chemistry, 48. pp. 7905-7091. ISSN 0020-1669

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    Abstract

    The design and development of suitable biomimetic catalytic systems capable of mimicking the functional properties of enzymes continues to be a challenge for bioinorganic chemists. In this study, we report on the synthesis, X-ray structures, and physicochemical characterization of the novel isostructural [FeIIICoII(BPBPMP)(μ-OAc)2]ClO4 (1) and [GaIIICoII(BPBPMP)(μ-OAc)2]ClO4 (2) complexes with the unsymmetrical dinucleating ligand H2BPBPMP (2-bis[{(2-pyridyl-methyl)-aminomethyl}-6-{(2-hydroxy-benzyl)-(2-pyridyl-methyl)}-aminomethyl]-4-methylphenol). The previously reported complex [FeIIIZnII(BPBPMP)(μ-OAc)2]ClO4 (3) was investigated here by electron paramagnetic resonance for comparison with such studies on 1 and 2. A magneto-structural correlation between the exchange parameter J (cm-1) and the average bond lengh d (A° ) of the [FeIII-O-MII] structural unit for 1 and for related isostructural FeIIIMII complexes using the correlation J = -107 exp(-6.8d) reveals that this parameter is the major factor that determines the degree of antiferromagnetic coupling in the series [(BPBPMP)FeIII(μ-OAc)2MII]þ (MII = Mn, Fe, Co, Ni) of complexes. Potentiometric and spectrophotometric titrations along with electronic absorption studies show that, in aqueous solution, complexes 1 and 2 generate the [(HO)MIII(μ-OH)CoII(H2O)] complex as the catalytically active species in diester hydrolysis reactions. Kinetic studies on the hydrolysis of the model substrate bis(2,4-dinitrophenyl)phosphate by 1 and 2 show Michaelis-Menten behavior, with 2 being 35% more active than 1. In combination with kH/kD isotope effects, the kinetic studies suggest a mechanism in which a terminal MIII-bound hydroxide is the hydrolysis-initiating nucleophilic catalyst. In addition, the complexes show maximum catalytic activity in DNA hydrolysis near physiological pH. The modest reactivity difference between 1 and 2 is consistent with the slightly increased nucleophilic character of the GaIII-OH terminal group in comparison to FeIII-OH in the dinuclear MIIICoII species.
    Item Type: Article
    Additional Information: The definitive version of this article is available in Inorganic Chemistry, 2009, 48, 7905–7921 DOI: 10.1021/ic900831q . © 2009 American Chemical Society
    Keywords: Unsymmetrical FeIIICoII; GaIIICoII Complexes; Chemical Hydrolases; Biomimetic Models; Purple Acid Phosphatases; PAPs;
    Academic Unit: Faculty of Science and Engineering > Chemistry
    Item ID: 3727
    Depositing User: Gary Schenk
    Date Deposited: 06 Jun 2012 07:40
    Journal or Publication Title: Inorganic Chemistry
    Publisher: American Chemical Society
    Refereed: Yes
    Related URLs:
    URI: https://mu.eprints-hosting.org/id/eprint/3727
    Use Licence: This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here

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