title: Spontaneous redox synthesis and characterization of the tetrathiafulvalene-vanadium-substituted polyoxometalate charge-transfer material TTF4[SVW11O40]: comparison with the Mo analogue.
abstract: Both conventional solution-phase and direct solid-solid redox reactions between tetrathiafulvalene (TTF) and the vanadium-substituted polyoxometalate (n-Bu4N)3[SV(V)W11O40] give rise to microcrystalline or powdered semiconducting charge transfer solid material. A single-crystal X-ray structure derived from growing crystals from a MeCN-CH2Cl2 solution-phase redox reaction gives a stoichiometry of TTF4[SVW11O40]·2H2O·2CH2Cl2 and reveals that there are two crystallographically different TTF cation moieties based on (TTF2)(2+) dimers. While the color and morphology of the microcrystalline or powdered TTF4[SVW11O40] differ from the single crystals prepared for structural analysis, all materials are spectroscopically (infrared (IR), Raman with respect to the TTF bands, and electron paramagnetic resonance (EPR)) indistinguishable. Raman spectra suggest that the charge transfer is unevenly distributed across the (TTF2)(2+) dimers, which is postulated to give rise to enhanced mixed-valence features. Structural, spectral, and other properties, such as conductivity, are compared with results available on the recently published molybdenum TTF4[SVMo11O40]·2H2O·2CH2Cl2 analogue, where the charge distribution is uniform on all TTF cations. In both examples, the position of the V atom is located over several sites. Elemental analysis and voltammetric data also are consistent with the formulations deduced from structural and spectroscopic studies. The conductivity at room temperature is in the semiconducting range, but significantly greater than that for the Mo analogue. EPR spectra at temperatures down to the liquid helium regime confirm the presence of paramagnetic V(IV) and paramagnetic oxidized TTF. The newly isolated TTF-SV(IV)W11O40 material also has magnetic functionality derived from the cationic and anionic components.
authors.affiliation: School of Chemistry, Monash University , Clayton, Victoria 3800, Australia.
authors.forename: Qi
authors.initials: Q
authors.lastname: Li
authors.forename: Jinzhen
authors.initials: J
authors.lastname: Lu
authors.forename: John F
authors.initials: JF
authors.lastname: Boas
authors.forename: Daouda A K
authors.initials: DA
authors.lastname: Traore
authors.forename: Matthew C J
authors.initials: MC
authors.lastname: Wilce
authors.forename: Lisandra L
authors.initials: LL
authors.lastname: Martin
authors.forename: Tadaharu
authors.initials: T
authors.lastname: Ueda
authors.forename: Alan M
authors.initials: AM
authors.lastname: Bond
mesh_terms: D018360:Crystallography, X-Ray; D055664:Electrochemical Techniques; D006571:Heterocyclic Compounds / Q000737:chemistry*; D008958:Models, Molecular; D008982:Molybdenum / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D010084:Oxidation-Reduction; D010316:Particle Size; D013499:Surface Properties; D017973:Tungsten Compounds / Q000737:chemistry*; D014639:Vanadium / Q000737:chemistry*; D000099294:Polyoxometalates
chemical_list: D006571:Heterocyclic Compounds; D008982:Molybdenum; D009942:Organometallic Compounds; D017973:Tungsten Compounds; D014639:Vanadium; C102296:polyoxometalate I; D000099294:Polyoxometalates; C063887:tetrathiafulvalene