| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2001: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 2000: ¥1,900,000 (Direct Cost: ¥1,900,000)
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| Research Abstract |
Raman and voltammetric studies were made for the formation of isopolyoxotungstates in aqueous and aqueous-organic media. Once [W_<10>O_<32>]^<4-> was formed in weakly acidified aqueous media, it was transformed spontaneously into Keggin-type [H_2W_<12>0_<40>]^<6->, and tungstate was precipitated as yellow oxide, WO_3 in more acidic solutions. On the other hand, the presence of organic solvents such as acetonitrile stabilized [W_<10>O_<32>]^<4-> , and we prepared a new Keggin complex, [H_4W_<12>0_<40>]^<4-> from such mixed media. We found that WO_3 was not precipitated in strongly acidified mixed media, owing to the conversion of [W_<10>O_<32>]^<4-> into [W_6O_<19>]^<2>, the formation of which prevented the precipitation of tungstate as the yellow oxide. As the results, we found the formation of novel polyoxotungstates such as tungstosulfate, tungstogallate, tungustotellurate, and tungstovanadate in acidified aqueous-organic media.
The formation of polyoxotungstatres has not been applied
… More
to the analytical purposes because the formation reaction is said to proceed very slowly. However, we found that a trace amount of various oxoanions reacted so rapidly with W(VI) to form the corresponding polyoxotungstates. On the basis of the formation of the polyoxotungstates with high molar absorptivities in the UV region, we developed highly sensitive CE methods for the determination of such oxoanions being capable of acting as the central hetero-ion. When the W(VI)-P(V) reagent was heated beforehand, a lacunary Keggin-type [PW_<11>O_<39>]^<7-> complex acted as a complexing reagent, and a variety of oxoanions could be determined through the ternary complex-formation. In the latter reagent method, oxoanions are incorporated in the peripheral position of the polyoxotungstate structure.
We found that polyoxometalates anions were adsorbed onto polypyrrole formed by the anodic oxidation of pyrrole at the glassy carbon electrode. On the basis of the findings, we developed high-sensitive adsorptive voltammetric methods for the determination of various oxoanions. Less
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