The Study On Solution Reaction Of Polyoxotungstates Cluster By ESI-MS

Transition metal-substituted polyoxometalate clusters?TMSPs?are an important component of polyacid chemistry.The introduction of transition metals into polyoxometalates gives them many new functional properties,such as magnetism,catalysis,medicine and materials chemistry.Vanadium-substituted polyoxometalates are particularly prominent in catalytic applications,and even some of these catalysts may undergo changes in the catalytic process.Its solution behavior is also very interesting because of the control of various reaction factors,in the reaction process occurs spontaneous transformation and recombination.With the isopolyoxotungstates cluster as another important branch of polyoxometalate clusters,its aqueous solution of the species and their transformation relationship between sensitive and complex changes.Therefore,it is very important to study the reaction mechanism and solution behavior of polyoxometalates.The electrospray ionization mass spectrometry?ESI-MS?,electrochemical differential pulse voltammetry?DPV?and density functional theory?DFT?were used to study the effect of transition metal vanadium(NaV^VO₃ and V^IVOSO₄ as vanadium sources)and lacunary polyoxotungstate.It is found that there are great differences in the process of solution reaction between different vanadium sources.The spontaneous transformation was observed during the reaction between NaV^VO₃ and the lacunary polyoxotungstate.The theoretical calculation also shows that this process is a thermodynamically exothermic process,which provides the basis for the experimental deduction.Take the place of NaV^VO₃ into V^IVOSO₄,the products behaved surprisingly stable during the monitoring,and the species was stable in the course of the reaction.The factors such as concentration and temperature could not affect the stable balance.The gas phase stability of{SiV_x^V/IVW_12-x}was investigated by ESI-MS/MS.The gas-phase stability of{SiV_x^IVW_12-x}as parent ion was greater than that of{SiV_x^VW_12-x},which was different for the different vanadium sources The experimental results also provide theoretical basis for the experiment.The experimental results show that the experimental results are in good agreement with the experimental results.The aqueous solution of paratungstate?NH₄?₁₀H₂W₁₂O₄₂ and the precursors of TBA₂W₆O₁₉ in acetonitrile were monitored by mass spectrometry.The MS and MS/MS results were analyzed and the gas phase stability was analyzed.The results show that ESI-MS is not likely to detect the true species status in the solution because of its tendency to degrade to low-nucleus tungsten in aqueous solutions and to the inter-species conversion in water.Cation exchange and other methods can reduce the hydrolysis and transformation,so that the existence of structural stability.