Sythesis And Characterization Of Dawson-type Tungstophosphates And Their Inorganic-organic Hybrid Compounds

Abstract:Polyoxometalates (POMs), a fascinating class of compounds with unique structural variety and physicochemical properties, which makes them suitable for photoelectron acceptor. Porphyrins are a kind of macrocyclic conjugated organic molecules which have an extensive system of delocalized π electrons, can be applied in electron transfer and energy conversion fields. The inorganic-organic hybrid compounds of donor-accepter based on porphyrins-POM have great light-harvesting ability. However, there are few reseach on design and synthesis new inorganic-organic hybrid compounds based on polyoxoanian clusters. In this thesis, a new method was used to synthesis Dawson-type tungstophosphates; two new inorganic-organic hybrid compounds based on Dawson-type tungstophosphoric heterpolyanions and porphyrins have been synthesized and structurally characterized.Strong acid acidification and ether extraction were used in conventional Dawson-type POM synthetic process which may lead to environmental pollution and safety hazards. In this thesis, Dawson-type polyoxoanian was synthesized by hydrotherml process, and the tungstophosphates can be precipitated from adding inorganic salts. The chemical composition of the products turn out to be K6P2W18O62·4H2O via elemental analysis and stucture characterization. The results indicate that the acidification pH of sodium tungstate solution and the hydrothermal conditions were key factors of [P2W18062]6-.The best synthetic conditions of K6P2W18O62·4H2O attributed to the acidification pH of sodium tungstate solution at1.8, hydrothermal temperture at160℃and hydrothermal time at8h.Two new inorganic-organic hybrid compounds have been designed and synthesized based on [P2W18O62]6-.The first one was base on Dawson-type trivanadium(V)-substituted tungstophosphoric polyoxoanion and zinc meso-tetrakis(4-N-carboxyphenyl)porphyrin, the second one was base on Dawson-type tungstophosphoric polyoxoanion and zinc meso-tetrakis(4-N-methylpyridyl)porphyrin. Elemental analysis and stucture characterization exhibits that the polyoxoanion and porphyrin component coexist in the structure through covalent bonds and electrostatic interactions. The successful synthesis of these two compounds proved that oranic group-grafting is one of the most effective ways to obtain POM-based materials. Moreover, the investigation of the interaction mechanism between polyoxoanion and porphyrin is great importance to understand the general rules of their interactions and shows reference value to the design of new inorganic-organic hybrid compounds as well.