| The introduction of hydrogen peroxide, DL-mandelic acid （H2Mal）, and/or acetate bufferinto the reaction system containing zirconium （IV） ions and various tri-vacantpolyoxometalates （POMs） led to the isolation of a series of new tetranuclearzirconium-substituted POMs modified by different O-donor ligands:Na4（NH4）14[Zr4（μ3-O）2（μ-O2）2（OAc）2(P2W16O59)2]51H2O （1）,（NH4）16[Zr4（μ3-O）2（Mal）2（H2O）2(P2W16O59)2]14H2O （2）,Na7（NH4）5[{Zr4（OH）6（OAc）2}(SiW10O37)2]·20H2O（3）,K4Na8[Zr4O2（C8H6O3）2（H2O）(GeW10O37)2]·11H2O（4）.All four compounds were characterized by the elemental analysis, IR spectra,thermogravimetric analysis （TGA） and single-crystal X-ray diffraction structural analysis.Compounds1and2possess similar sandwich-type polyoxoanions built from a tetranuclear Zrcluster and two [P2W16O59]12building blocks, except that the modifying ligands on the {Zr4}clusters are peroxide and mandelate for1and2, respectively. The polyoxoanion of3containsa different tetranuclear Zr cluster, which is further sandwiched by two [α-SiW10O37]10moieties and decorated by two acetate ligands. The polyoxoanion of4also contains atetranuclear Zr cluster, which is decorated by two Mal ligands and sandwiched by two[GeW10O37]10moieties. The catalytic activities of1-3were evaluated based on a catalyticoxidation reaction of peroxidase substrate3,3’,5,5’-tetramethylbenzidine （TMB） by H2O2.Compound1exhibits the best catalytic activity, suggesting a new peroxidase-like catalyst forthe colorimetric detection of H2O2with a linear detection range from100to1000μM （r=0.997） and a detection limit of100μM. |
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