Peroxovanadates and Its Bio-Mimicking Relation with Vanadium Haloperoxidases

Peroxovanadates and Its Bio-Mimicking Relation with Vanadium Haloperoxidases

Pranjal Saikia (Gauhati University (IST), India), Saitanya Kumar Bharadwaj (Pragjyotish College, India) and Abu Taleb Miah (Gauhati University (IST), India)
Copyright: © 2016 |Pages: 23
DOI: 10.4018/978-1-4666-9811-6.ch007
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Vanadium Haloperoxidases (VHPOs) have been used in a variety of biotransformations showing remarkable stereoselectivity and regiospecificity. The high efficiency of the enzyme is influenced by the protein active site and the role of certain amino acids in activation of vanadium(V)-bound peroxide for halide oxidation. The use of natural or recombinant enzymes, or biomimetic vanadium compounds brings up issues regarding the cost of production and reaction conditions. In this chapter, the primary intent is to provide a simple and clear picture of functional mimicking nature of peroxovanadium compounds with haloperoxidases enzymes to the readers. Major emphasis would be given to examine the reactivity of the vanadium haloperoxidases with mechanism.
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1. Introduction

Peroxo vanadium compounds are one of the most interesting aspects not only for its roles in biological processes but also for catalytic oxidations. It may be mentioned, while discussing the peroxo chemistry, that addition of two extra electrons to 2Pπ* orbital of molecular oxygen results in peroxide (O22-) formation and decreases the O-O bond order. As a result, reactivity of peroxo compound differs from unreduced dioxygen complexes. The modes of bonding of peroxide to metals are quite varied and interesting from the structural viewpoint. It can range from a symmetrical bidentate to a terminal monodentate position including all the possible angles in between. The bridging μ-peroxo could vary from cis-planar and trans-planar to trans-nonplanar configurations. Based on the mode of binding, Vaska (1976) classified the complexes as depicted in Table 1.

Table 1.
Vaska’s classification of peroxo complexes
Structural TypeStructural DesignationExample
η2 (superoxo)[Co(CN)5(O2)]3-
η2 (peroxo)
η2 (superoxo)
η1: η1 (peroxo and superoxo){[Cu(TMPA)]2(O2)}2+
η2: η2 (peroxo)[Cu(O2)(HB(3, 5-iPr2pz)3)]2(O2)
[Cu(α-isosparteine)]2 (μ-η2:η2-O2)(coo-)
η1: η2 (peroxo)[(PO4)W4O4(O2)8]3-
Cs3[V2 O2(O2)4F]

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