Substituent effect in the electrochemistry of Dawson-type tungstodiphosphates: Some strategic parameters for apparently multiple electronation on the first wave of heteropolyanions

• Published in: Journal of electroanalytical chemistry (Lausanne, Switzerland) Vol. 442; no. 1; pp. 49 - 57
• Main Authors: Keita, B, Belhouari, A, Nadjo, L, Contant, R
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 30-01-1998; Elsevier Science
• Subjects: Chemistry; Cyclic voltammogram; Electrochemistry; Exact sciences and technology; General and physical chemistry; Heteropolybues; Kinetics and mechanism of reactions; Spectroelectrochemistry; Waves; Spectroelectrochemistry; Waves; Heteropolybues; Cyclic voltammogram; Heteropolysalt; Vacancy; Sodium Sulfates; Transition metal Complexes; Experimental study; Carbon; Acidic solution; Sulfuric acid; Electrodes; Tungsten Complexes; Absorption spectrometry; Electrochemical properties; Medium effect; Iron Molybdenum Tungsten Complexes; Heteronuclear complex; Iron Tungsten Complexes; Polynuclear complex; pH; Spectrophotometry; Glassy state; Ultraviolet visible spectrometry
• ISSN: 1572-6657; 1873-2569
• DOI: 10.1016/S0022-0728(97)00191-5

The lacunary species
α
1 and
α
2P
2□W
17C
61
10− and the corresponding iron-substituted derivatives have been studied and compared. For a given pH value, the cyclic voltammograms are influenced by the location of the vacant W site in the framework. The influence is strong in the
α
1 but hardly exists in the
α
2 substituted derivative. This observation is ascribed mainly to the large framework distortion induced by the vacancy in the
α
1 site. The effect is found to favour coalescence of waves. Lower and lower pH media also favour the merging of waves. The combination of the effects of these two parameters is shown to be beneficial for the observation of multiple electronation on the first wave of heteropolyanions in very mild conditions. Spectroelectrochemistry experiments support completely the conclusion that conditions can be found in which the iron and heteropolyanion waves mix up. Another series of heteropolyanions,
α
2P
2□W
15Mo
2O
61
10−,
α
2P
2W
15Mo
3O
62
6− and
α
2P
2W
15Mo
2O
61Fe(OH
2)
7−, has permitted the effects of these parameters to be confirmed and also gives a preliminary insight into their interplay with the nature, the number and locations of the substituents in the tungsten framework.