A DFT Study Of The Electronic Properties And Relative Stability On [H_nP₂Mo₅O₂₃]～((6-n)-) And α/β-Keggin [SiW₉Al₃(H₂O)₃O₃₇]～(7-) Polyan

Polyoxometalates exhibit remarkable photic, electrical, magnetic and catalytic properties and diversity of molecular and electronic structure. With the development of investigation, polyoxoanion chemistry has attracted considerable interest spanning a variety of fields, including chemical analysis, medicine, catalysis, biology, material and photochemistry.The quantum chemistry calculation was introduced to the polyanion chemistry. The electronic and catalytic properties have made achievement using semi-quantum chemistry method. However, there is still a need for a systematic analysis of the molecular and electronic structure of heteropoly compounds, redox, catalytic, electrochemistry, magnetism and nonlinear optical properties as well as the redox and catalytic mechanism. It is essential that high-level calculations on electronic structure catalytic activity and mechanism of polyoxometalates are carried out so that experimental synthesis could be guided and predicted.In this thesis, we report the electronic properties, relative stability and reactive activity of [HnP2Mo5O23](6-n)- and -/ -[SiW9Al3(H2O)3O37]7-which standard geometrical parameters were taken from experiment. Theresults are followed:1 The [HnP2Mo5023](6-n)- was firstly studied by using density functional theory (DFT) methodology, the geometrical parameters are in agreement with experimental data. The degree of protonation influences on the geometric structure and electronic property. For [HnP2Mo5O23](6-n)-, the results show that the nucleophilic active sites concentrate on bridgingoxygen atoms and the electrophilic active sites concentrate on terminal oxygen atoms. The higher the degree of protonation is, the higher the electrophilic and nucleophilic reactivities are higher.2 The electronic properties, relative stability and reactive activity of / -[SiW9Al3(H2O)3O37]7- have been analyzed by using the quantum-chemical density functional theory (DFT) methodology. The analysis of bonding energy showed that suggest that the a-isomer is more stable than -isomer. The -isomer is more easily reduced than a-isomer because the (3-isomer has a smaller (H-L) gap and a lower energy of LUMO.