Syntheses of Lanthanide-containing Polyoxotungstates Substituted by Transitionmetal-Nonmetal pairs : Its Developments for Photo-electron Molecular Catalysts

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In 2000 : Synthesis of lanthanide decatungstates substituted by two-vanadium ions[LnV2W8] have been variously attempted. Further, LnV2W8 thus obtained was tried to fix on titanium-oxide-hydroxides[TiO(OH)2] with silane agents. Photocatalytic oxidation of hydrocarbons were examined prelininarly on LnW10, and effects of various transition metal ions added to LnW10 on the photocatalytic activities were compared, as previously reported. In 2001 : Modification of LnV2W10 with organic group[org-LnV2W8] and further fixzation of LnV2W8 and org-LnV2W8 on TiO(OH)2 modified previously with silane agents[sil-TiO2] were attempted variously to obtain LnV2W8/sil-TiO2 and org-LnV2W8/sil-TiO2 catalysts. Those samples were successfully analyzed by FT-IR,UV-vis,ICP,ESR, so on. 1)The catalytic activities of LnV2W8 for H2O2-oxidation of hydrocarbons were greatly enhanced with the V2-substitution, LnV2W8 ; the activities for methyl-sulfide, 2-hexene-1-ol, and menthol increased ca.4-times,3-times, and 2-times, respectively. Especially, org-LnV2W8/sil-TiO2 catalyst showed an excellent activity for H2O2-oxidation of hydrocarbons in an organic solvent free system, being very suitable from a viewpoint of green catalyst chemistry. 2)ESR-measurements of org-GdV2W8/sil-TiO2 were taken place under UV-light irradiation ; changes in the intensities of ESR-signals among Gd(III),V(IV), and Ti(III) on TiO2,accompanied with an electron-transfer, were compared and also those changes were examined under introducing organic gasses. 3)Measurements of variations in UV-vis and fluorescence spectra, accompanied with the changes in the intensities, are now in progress. 4)Syntheses of new LnW10 samples as substituted simultaneously by vanadium and silanol-groups, and their fixzation on sil-TiO2 have been attempted. 5)Photo-catalytic activities of LnW10 were enhanced greatly in the combination with Cu(II) and Cu(II)+Pd(II) ions, for instance, for photo-catalytic oxidation of alcohols.