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://mural.maynoothuniversity.ie/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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