Ferrocene Derivatives With Poms-based Charge-transfer Salts And Several New Sandwich Heteropoly Molybdate Research

Polyoxometalates (POMs) have received great interest due to an enormous structural variety and interesting properties leading to applications in catalysis, medicine, magnetochemistry, and materials science. POMs are well-known electron acceptors and the ferrocene and its derivatives are a type of potential candidates as organometallic electron donors, they can form the organic-inorganic hybrid materials with expected synergetic properties, such as charge-transfer transition, magnetism, electrical conductivity and nonlinear optical properties.This thesis focused on the following two aspects:In the first part, eleven new charge-transfer salts (CTSs) based on ferrocenyl donors and different types POMs acceptors were synthesized by chemical solution molecular self-assembly method, namely,CTSs based on Keggin POMs acceptors: [Fe(Cp)2]4[HSiMoⅤMoⅥ11O40]·2CH3CN-H2O(1) [CpFeCpCH2N(CH3)3]3[PW12O40] (2) [CpFeCpCH2N(CH3)2C2H5]4[PMoⅤMoⅥ11O40] (3) [CpFeCpCH2N(CH3)2C2H5]4[SiW12O40](4) (Bu4N)[CpFeCpCH2Py]2[PMo12O40](5)CTSs based on Lindqvist POMs acceptors: [CpFeCpCH2N(CH3)2C2H5]2[Mo6O19](6) [CpFeCpCH2N(C2H5)2CH3]2[W6O19](7) (Bu4N)[CpFeCpCH2N(C2H5)3][Mo6O19](8) (Bu4N)[CpFeCpCH2N(C2H5)3][W6O19](9)CTSs based on decatungstate POMs acceptors: [CpFeCpCH2N(CH3)2C2H5]4[W10O32](10) [CpFeCpCH2Py]4[W10O32] (11)Their structures were determined by X-ray diffraction analysis, and they were characterized by IR, UV-vis, CV, diffuse reflectance and fluorescence spectra. All the elven CTSs were synthesized in the heated CH3CN solution and cocrystallized by self-assembly, in which the CTSs containing CpFeCpCH2N+(CH3)2C2H5 cation, CpFeCpCH2N+CH3(C2H5)2 cation, CH3CpFeCpCH2N+(C2H5)3 cation, [W10O32]4- polyanion, and with the ratio of ferrocenyl:POM of 1:1 are unprecedented to our knowledge. The experiments show that large substituent group on Cp is favorable to the formation of CTSs with low ratio of ferrocenyl:POM. In the solid state the polyanions and ferrocenyl cations are intereacted by non-covalent bond (Coulombic forces, hydrogen bond,π…πstacking and other supermolecular interactions). IR spectra analysis indicates that the characteristic peaks of polyanion and ferrocenyl cation change both in the strength and position compared with the starting materials; new absorption bands was observed in the diffuse reflectance spectrum of the compounds in solid state; and the fluorescence spectra were obviously distinct (stengthened or weakened, and even quenched) compared to materials, all of these are attributed to charge transfer between cationic ferrocenyl donor and anionic POMs acceptor, and the absorptions in the diffuse reflectance spectra are related to the reduction potentials of the acceptor moiety. The UV-vis spectra and CV curves of the title compounds in weak coordination acetonitrile solution indicated the cations and polyanions simply coexist without any significant interaction in solution.In the second part, three new dinuclear sandwich-type heteropolymolybdates based on novel inorganic fragment [AsⅢMo7O27]9- were synthesized and characterized by elemental analyses, IR, UV, TG analyses, CV and single-crystal X-ray diffraction, and their magnetic properties are thoroughly investigated. Namely, (NH4)12[Fe2(AsMo7O27)2]·12H2O(12) (NH4)12[FeCr(AsMo7O27)2]·13H2O(13) (NH4)10[Ti2(AsMo7O27)2]·18H2O(14)Compound 13 is the first example of the "symmetrical" heterometallic sandwich POM and 14 is the first example of substituted containing titanium sandwich heteropolymolybdate. X-ray structural analysis revealed that the three compounds are isostructural and consist of two novel monocapped hexavacant subunit polyanion [AsⅢMo7O27]9- moieties sandwiched an central{MM'O10} (MM'=FeFe, CrFe, TiTi) cluster, leading to a dinuclear transition-metal substituted sandwich-type structure with C2v symmetry. The IR spectra present a lower absorption ofμ(Mo=Od) compared with those of most POMs due to each Mo atom in the polyanions with at least two long Mo=Od bonds. The profile of time-dependent UV-vis spectra showed a distinct decrease in intensity compared to fresh sample, which may mean that the compounds are unstable in the aqueous solution. Three compounds have approximately thermal decomposition process, corresponding to lose of all water and NH3 molecules, the escaping of AS2O3 and the decomposition of the Mo-MM'-O framework structure, and the final products are the mixture of metal oxides and MoO3. The magnetic studies indicated a significant antiferromagnetic exchange interactions between the two central transition metal ions bridged by twoμ-O, and unambiguously established that [FeCr(AsMo7O27)2]12- contains a bimetallic Cr(III)-Fe(III) unit and (NH4)12[FeCr(AsMo7O27)2]·13H2O (13) is not a mixture of the two antiferromagnetically coupled homometallic species.