Synthesis,Structures And Physicochemical Properties Of Polyoxometalates Derivatives Functionalized By Organic Ligands

The aim of this thesis is to create a new series of covalently bonded inorganic-organichybrid materials based on polymolybdate clusters by exploiting appropriate metal cations ororganic ligands as linkers according to the concept of crystal engineering. A series ofcompounds have been synthesized and characterized by means of DCC method, aqueoussolution reaction conditions and hydrothermal reaction conditions. The physical and chemicalproperties of these compounds, such as thermal stabilities and redox electrochemicalbehaviors, have also been researched in detail. These compounds are below:(Bu₄N)₂[Mo₆O₁₇(NAr)₂] [Ar = 2,6-(CH₃)₂C₆H₃] (1)(phen)₂[Cu₂(ac)₂(H₂O)₂(CrMo₆H₆O₂₄)]·10H₂O (2)Na₃(Himi)(imi)( NiMo₆H₆O₂₄)·H₂O (2) , (3)Na₂[Cu₃(OH)₄(H₂O)₄][β–Mo₈O₂₆]·13H₂O (4)[Co(H₂O)₅]₄[ Co(H₂O)₄][H₃O]₂[Mo₇O₂₄]₂·18H₂O (5)Na[Cu(imi)₂]₇[As₂W₁₈O₆₂]·5 H₂O (6)[Cu(CH₃-imi)₂]₅[AsW₁₂O₄₂]·2 H₂O (7)[Cu(CH₃-imi)₂]₅[PW₁₂O₄₂]·2 H₂O (8)[Cu(CH₃-imi)₂]₅[H₂W₁₂O₄₂]·2 H₂O (9)[Ag(imi)₂]₅[PW₁₁O₃₉Co(imi)]·3 H₂O (10) Compound 1 was synthesized according to DCC method. The formation of covalentbonds between organic fluorescence molecule and polyoxometalate could efficiently quenchthe fluorescence intensity of organic fluorescence molecule, with a fluorescence quencherefficiency of 87.7%. Compound 2 and 3 were obtained in aqueous solution illustrating 1Dchannels in the structure. Compound 4 and 5, possessing 3D covalently bonded architecture,were also synthesized in aqueous solution. Compound 6-10 were synthesized viaself-assembly under hydrothermal reaction conditions. It is noteworthy that compound 10,taking into account the supramolecular interactions in the structure, has the architecture ofpolypseudo-rotaxane. X-ray diffraction analysis reveals that 10 comprises cationic Ag(imi)2nn-two-dimentional (2D) netlike frameworks parallel to the [0 1 0] direction. To the best of ourknowledge, 10 is the first 1D-in-2D entangled system incorporating polyoxometalates. Thetitle compound 10 has potential application in fluorescencent materials due to the intenseemission at 469nm.All these compounds are highly insoluble in water and common organic solvents due tothe covalently bonded interactions. Therefore, most of these compounds are employed tofabricate the three-dimensional bulk-modified carbon paste electrodes (CPEs) to research ontheir electrochemistry and electrocatalytic properties towards the reduction of chlorate,hydrogen peroxide and nitrite. Compared with those conventional POM-modified electrodes,these hybrid-modified CPEs show good stability owing to their insolubility in aqueoussolution.