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 |
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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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