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

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)] (PA(3)), [V2O2(O-2)(4)(carboxylate)VO(O-2)(2)-(sulfonate)]-PSSM [PSSM = poly(sodium styrene sulfonate-comaleate)] (PV4), [Mo2O2(O-2)(4)(carboxylate)]-PA [PA = poly-(sodium acrylate)] (PMo1), [MoO(O-2)(2)(carboxylate)]-PMA [PMA = poly(sodium methacrylate)] (PMo2), and [MoO(O-2)(2)-(amide)] -PAm [PAm = poly(acrylamide)] (PMo3) by reacting V2O5 (for PV3 and PV4) or H2MoO4 (for PMo1, PMo2, and PMo3) with H2O2 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, C-13 NMR, V-51 NMR, and Mo-95 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 100 times weaker as substrate to the enzyme catalase relative to H2O2 its natural substrate. The effect of the title compounds, along with previously reported compounds [V2O2(O-2)(4)(carboxylate)]-PA (PV1) and [VO(O-2)(2)(carboxylate)]-PMA (PV2) 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)(H2O)] (DPV), [MoO(O-2)(2)(glycine)(H2O)] (DMo1), and [MoO(O-2)(2)(asparagine)(H2O)] (DMo2). 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.