The Study Of Arsenictungstenic Sandwiched Polyoxometalates Synthesis Structure And Photochromic Effects

In recent years, people have payed more and more attention to sandwich complexesmade of polyoxometalates and transition metals. Because these complexes not only simplymix the properties of the two kinds of reactants, but also produce superior value-addingproperties—they possess excellent optical, electrical and magnetic qualities. In our work , thereactions between the relative new kind of polyoxometalate anion α-{AsW₁₅(OH)₄O₅₂}^13–and divalent Mn²⁺ or Co²⁺ ions in aqueous medium led to the formation of two newsandwich-type complexes Na2[αββα-(Mn₄^â…¡(H₂O)₂)(AsW₁₅(OH)₁₂O₄₄)₂]·30H₂O(1)and Na₅H₅[αββα-(Co^â…¡(H₂O)₅)₂(Co₄^â…¡ (H₂O)₂)(AsW₁₅ (OH)₆O₅₀)₂]·38H₂O(2). Both complexeswere characterized by elemental analyses, single crystal X-ray diffractions and IR spectra. Inboth 1 and 2, rhombic tetrametic clusters X4O16 (X= Mn, Co) are sandwiched between twovacant [AsW₁₅(OH)₄O₅₂]^13-, but two mononuclear Co(II) coordinate octahedra are attachedoutside the sandwich complex in 2. Although the two complexes were synthesized by theanalogous method with the same building block of [AsW₁₅(OH)₄O₅₂]^13-, they exhibitobviously different crystal packing motifs in which complex 2 appears in an extended 2Dnetwork, while complex 1 displays a discrete arrangement of clusters in two differentorientations. In comparison with the sandwich-type complex of Mn₄(As₂W₁₅)₂, theelectrochemical behavior of complex 1 {Mn4(AsW₁₅)₂}shows a negative shift of theoxidation potential of Mn(II) wave. In the temperature range 2-300 K, the ferromagneticinteraction is dominant magnetic behavior for either 1 or 2, though the ferromagneticcoupling is stronger in 2 than in 1.Secondly,it has been few works on photochromic effects of polyoxometalate-sandwichedcomplexes. In this article, we examed our two sandwiched complexes in different organicsolvents on their photochromic effects.We found they could change colours in organicamines.On the base of this finding ,we researched the systems through spectra and comparedthe differences between polyoxometalate and its sandwiched complexes on the effects,attempting to give the mechanism of their photochromic effects.In addition, for a long time, there have been increasing efforts towards makingmultifunctional hybrid materials by using covalently linked polyoxometalates (POMs) andorganic polymers. The motivation lies not only in the combination of the so-calledvalue-adding properties, but also in the exploration of possible synergistic effects. Forexample, the covalent grafting of electron-accepting POMs into an organic conjugatedpolymer may result in highly photoconductive materials with photochromic effects. In ourwork, we tried to use ultraviolet to irradiate diphenylamine diazonium salt, hoping to producecarbon cation and make the cation react with the exterior oxygen atoms of polyoxometalateshich has a relative excessive electron density. We expected diphenylamine diazonium saltand polyoxometalates to connect with covalent bond. We tried many ideas and attemptedmany different ways to bring up crystals, thout success in the end. But we did geta kinwhowever, wid of crystal which is pieces of H3PMo12O40. It was broke into pieces by UV radiation. Inthis way, we made something available for the synthesizing of hybrid materials.