The Activation Of POM Units And Construction Of POM-Based Highnuclear Clusters

Polyoxometalate（POM）-based high nuclear clusters are attracting ongoing tremendous research interest due to their unique structural diversity and their potentials for a wide range of applications. The coexistence, activation, and self assembly of different kinds of building blocks are the key factors in the study of this field. The design and synthesis of high nuclear clusters based on lacunary POM building blocks and a series of bridging units with different methods are the main work of this paper.Seven giant metal-oxo clusters have been constructed from a dynamic POM building block {B-É‘-Sb^IIIW₉O₃3}, lanthanide（Ln） linkers and a small organic fragment 2-picolinic acid（Hpic） via a stepwise synthetic strategy. It is the first time the {Sb₃O₄} fragment has been introduced as a unique linker into high nuclear clusters. The syntheses, structures and luminescent properties of these compounds were investigated.Na₄Li₆[La₂（H₂O）₄{WO₂（pic）}₂（SbW₈O₃0）₂]?28H₂O, [La-1]Na₃Li₇[Pr₂（H₂O）₄{WO₂（pic）}₂（SbW₈O₃0）₂]?17H₂O, [Pr-2]K₂Na₆Li₁6[{Tb（H₂O）}{Tb（pic）}（Sb₃O₄）（SbW₈O₃1）（SbW₁0O₃5）]₂?63H₂O, [Tb-3]Na₉Li₁5[{Dy（H₂O）}{Dy（pic）}（Sb₃O₄）（SbW₈O₃1）（SbW₁0O₃5）]₂?61H₂O, [Dy-4]Na₇Li₁7[{Ho（H₂O）}{Ho（pic）}（Sb₃O₄）（SbW₈O₃1）（SbW₁0O₃5）]₂?53H₂O, [Ho-5]Na₆Li₁6[{Y（H₂O）}{Y（pic）}（Sb₃O₄）（SbW₈O₃1）（SbW₁0O₃5）]₂?51H₂O, [Y-6]Compounds 7-9 were obtained by the self-assembly of the precursor {XW₉O₃3}（ X = As,Sb, Bi）, molybdenum oxygen clusters and Hpic fragments. In this paper, we show 7 and 8possess intrinsic peroxidase-like activities and can catalyze the oxidation of peroxidase substrate 3,3’,5,5’-tetramethylbenzidine（TMB） by H₂O2 to develop a blue color in aqueous solution, which leads to a simple method towards colorimetric detection of H₂O2. We also study the effect of reaction time, pH and concentration of H₂O2 to the catalytic reaction, and the results show the color deepens with the increasing of reaction time and the concentration of H₂O2, and the catalytic reaction solution show the deepest blue at pH 4 in the range 3 to 8.Na（NH₄）₆[{MoO₂（pic）}₂（SbW₈MoO₃3）]·15H₂O POM 7Na（NH₄）₆[{MoO₂（pic）}₂（AsW₈MoO₃3）]·15H₂O POM 8[NH₄]₁4[Bi₂W₂0Mo₂O₇6]·6H₂O POM 9...