Voltammetric Characterization of α- and β-Dodecamolybdophosphates in Aqueous Organic Solutions

Abstract

The electrochemical properties of α- and β-dodecamolybdophosphates were characterized at the glassy carbon (GC) electrode. It was found that the β-isomer was only stable in neat organic solvents. When molybdophosphate was prepared in aqueous organic solutions, a mixture of α- and β-isomers formed.

Redox chemistry of the Keggin heteropolyoxotungstate anion in ionic liquids

“…Specifically, we have exploited 1,3-dialkylimidazolium salts that are liquid at room temperature as dual purpose media-solvent and electrolyte -in which to study the electrochemical response of the Keggin polyoxoanion. Although this response is thoroughly understood [7,[22][23][24][25][26][27][28][29] in conventional solvents, both aqueous and organic, which require the use of added supporting electrolytes, no reports of POM electrochemistry in ILs have appeared to date.…”

Effects of Organic Solvents and Salts on the Isomerization Reaction (β→α) of Keggin-type 12-Molybdophosphate Anion

“…The first and second redox waves corresponded to two two-electron redox processes of the β-PMo12 anion, and the second and third redox waves corresponded to those of α-PMo12. 23 Three 31 P NMR peaks for the same solution as in Fig. 1(a) were obtained at 0.46, -2.63 and -2.93 ppm, which were assigned as free phosphate ion, β-PMo12 and α-PMo12, respectively, by taking into consideration the organic solvent effect on the chemical shifts.…”

“…22 The isomerization of β-PMo12 into the α-form was examined only in aqueous-40% (v/v) organic mixed media. 23 However, there have been only a few reports on the mechanism of the isomerization reaction of β-Keggin anions into α-Keggin anions, while a number of reports have been published on the synthesis of polyoxometalates. In aqueous solution, the isomerization reactions (β1→β2→β3→α) of lacunary species [SiW11O39] 8-and [AlW11O39] 9-have been investigated.…”

Vanadium‐Substituted Tungstophosphoric Acids as Efficient Catalysts for Visible‐Light‐Driven Oxygenation of Cyclohexane by Dioxygen

“…The CV curve of the PW 12 acid revealed two pairs of quasi-reversible redoxw aves near (À0.071-0.403)/2 = À0.237 and (À0.279-0.572)/2 = À0.426 Vi n the scanning range À1.2-1.7 V (curve a), which should be assigned to the redoxp rocess between W 6 + and W 5 + ions. [62] In comparison with the PW 12 acid, the one V-containing PW 11 V 1 acid also exhibited similar W 6 + /W 5 + redox waves in its CV curve (curve b). In addition, ap air of weak and quasi-reversible redox waves at (0.760 + 0.610)/2 = 0.685 Vc ould be noticed in its CV curve, which should be assigned to the redox process between V 5 + and V 4 + ions.…”

“…In addition, ap air of weak and quasi-reversible redox waves at (0.760 + 0.610)/2 = 0.685 Vc ould be noticed in its CV curve, which should be assigned to the redox process between V 5 + and V 4 + ions. [62][63] Notably,i ftwo or three Vatoms were incorporated into the PW heteropolyacid, its W 6 + /W 5 + redox waves were significantly weakened and the reductivep eak becames hiftedt oward am ore positive potential region (curves ca nd d) Concomitantly,apair of quasi-reversible V 5 + /V 4 + redox waveso nP W 10 V 2 and PW 9 V 3 became very strong and shifted towardamore positive potential region (respectively appearing at (0.978 + 0.557)/2 = 0.772 Vand (0.961 + 0.456)/2 = 0.709 V). This should be caused by the fact that the vanadium atoms incorporated into the Keggin structuralh eteropoly acid lead to enhanced reoxidationa ctivity.…”