Polymer-Anchored Peroxo Compounds of Vanadium(V) and Molybdenum(VI): Synthesis, Stability, and Their Activities with Alkaline Phosphatase and Catalase

Abstract

We generated a series of new polymer-bound peroxo complexes of vanadium(V) and molybdenum(VI) of the type [VO(O(2))(2)(sulfonate)]-PSS [PSS = poly(sodium 4-styrene sulfonate)] (PV(3)), [V(2)O(2)(O(2))(4)(carboxylate)VO(O(2))(2)(sulfonate)]-PSSM [PSSM = poly(sodium styrene sulfonate-co-maleate)] (PV(4)), [Mo(2)O(2)(O(2))(4)(carboxylate)]-PA [PA = poly(sodium acrylate)] (PMo(1)), [MoO(O(2))(2)(carboxylate)]-PMA [PMA = poly(sodium methacrylate)] (PMo(2)), and [MoO(O(2))(2)(amide)]-PAm [PAm = poly(acrylamide)] (PMo(3)) by reacting V(2)O(5) (for PV(3) and PV(4)) or H(2)MoO(4) (for PMo(1), PMo(2), and PMo(3)) with H(2)O(2) and the respective water-soluble macromolecular ligand at pH 5-6. The compounds were characterized by elemental analysis (CHN and energy-dispersive X-ray spectroscopy), spectral studies (UV-vis, IR, (13)C NMR, (51)V NMR, and (95) Mo NMR), thermal (TGA) as well as scanning electron micrographs (SEM), and EDX analysis. It has been demonstrated that compounds retain their structural integrity in solutions of a wide range of pH values and are approximately 100 times weaker as substrate to the enzyme catalase relative to H(2)O(2), its natural substrate. The effect of the title compounds, along with previously reported compounds [V(2)O(2)(O(2))(4)(carboxylate)]-PA (PV(1)) and [VO(O(2))(2)(carboxylate)]-PMA (PV(2)) on rabbit intestine alkaline phosphatase (ALP) has been investigated and compared with the effect induced by the free diperoxometallates viz. Na[VO(O(2))(2)(H(2)O)] (DPV), [MoO(O(2))(2)(glycine)(H(2)O)] (DMo(1)), and [MoO(O(2))(2)(asparagine)(H(2)O)] (DMo(2)). It has been observed that although all the compounds tested are potent inhibitors of the enzyme, the polymer-bound and neat complexes act via distinct mechanisms. Each of the macromolecular compounds is a classical noncompetitive inhibitor of ALP. In contrast, the action of neat pV and heteroligand pMo compounds on the enzyme function is consistent with a mixed type of inhibition.

Macromolecular peroxo complexes of Vanadium(V) and Molybdenum(VI): Catalytic activities and biochemical relevance

“…61,62 The results are also consistent with the proposed structures of the pMo containing macrocomplexes PMo 1 , PMo 2 and PMo 3 presented in figure 2a-c. 62 The metal loading on the compounds, estimated on the basis of Energy Dispersive X-ray (EDX), atomic absorption spectroscopy (AAS) and elemental analysis data was found to vary within the range 2.1 (PV 1 ) to 0.7 (PMo 3 ) mmol g −1 of polymer. 61,62 The scanning electron micrographs of the polymer anchored complexes (figure 3) revealed that the metal ions are distributed across the surface of the polymers. The 51 V NMR spectra of PV 1 and PV 4 are presented in figure 4.…”

“…61,62 Most notable finding of our study was that the polymer anchored and neat peroxo compounds induced their inhibitory effects on ALP via distinct mechanisms. 62,63 Moreover, polymer bound pV 61 and pW complexes 65 efficiently mediated oxidative bromination of organic substrates under mild condition at near neutral pH, considered as essential requirement of a biomimetic model. It was observed that even a minor change in co-ordination environment around the peroxometal moieties in the polymeric complexes could alter their bioactivity as well as their catalytic activity tremendously.…”

“…86 We have prepared a series of polymer bound peroxo complexes of vanadium(V) and molybdenum(VI) of the type,[ with H 2 O 2 and the respective water soluble macromolecular ligand at pH 5-6. 61,62 In a solution of vanadate or molybdate and excess H 2 O 2 at a pH ≥ 5, formation of diperoxo species of these metals is favoured. 16,87,88 We have observed that formation of the [MO(O 2 ) 2 ] (M = V or Mo) moieties and their coordination to the macroligands occurred optimally at near neutral pH.…”

“…[64][65][66] Interestingly, the soluble macrocomplexes exhibited unique oxidant activity as well as biochemical properties including anti-bacterial 61 and enzyme inhibitory activities. 62,63 Significantly, immobilization of the pV and pMo species enhanced their stability as well as their ability to resist degradation under the effect of the enzyme catalase. 61,62 Most notable finding of our study was that the polymer anchored and neat peroxo compounds induced their inhibitory effects on ALP via distinct mechanisms.…”

“…62,63 Significantly, immobilization of the pV and pMo species enhanced their stability as well as their ability to resist degradation under the effect of the enzyme catalase. 61,62 Most notable finding of our study was that the polymer anchored and neat peroxo compounds induced their inhibitory effects on ALP via distinct mechanisms. 62,63 Moreover, polymer bound pV 61 and pW complexes 65 efficiently mediated oxidative bromination of organic substrates under mild condition at near neutral pH, considered as essential requirement of a biomimetic model.…”