Peroxotungstates and Their Citrate and Tartrate Derivatives

Abstract

The reaction of potassium tungstate with the biologically relevant ligands citric and tartaric acid, in the presence of hydrogen peroxide, was investigated to discover the effect of pH variation on the product pattern.

Spectroscopic and DFT Study of Tungstic Acid Peroxocomplexes

“…22 A series of peaks associated with phenylphosphonic acid are also present in addition to the band at 950 cm -1 assigned to the WdO vibration. 21,22 DFT calculations aimed at describing the vibrational structure of the three species by way of a good agreement with the experimental infrared spectra (Figure 2). The main differences between experimental and theoretical vibration bands can be attributed to the interaction between clusters in the solid, which cannot be taken in the model employed in the calculations.…”

“…The infrared spectrum of the (HO) 2 WO 2 sample diluted in potassium bromide revealed the characteristic vibration bands of this compound (Figure 1). This spectrum shows a broad band at 600-700 cm -1 attributed to W-O‚‚‚HO-W, W-O-H, and W-O-W bond vibrations 21,22 and a sharper band at 950 cm -1 assigned to WdO bond vibration. 21,22 The peak observed at 1620 cm -1 is due to the OH bending of molecular water absorbed in the KBr pellet.…”

“…This spectrum shows a broad band at 600-700 cm -1 attributed to W-O‚‚‚HO-W, W-O-H, and W-O-W bond vibrations 21,22 and a sharper band at 950 cm -1 assigned to WdO bond vibration. 21,22 The peak observed at 1620 cm -1 is due to the OH bending of molecular water absorbed in the KBr pellet. The spectrum of tungstic acid treated with hydrogen peroxide shows clear differences.…”

“…22 Additional bands around 560 cm -1 belong to ν as W(O-O) and ν s W(O-O). 22 A series of peaks associated with phenylphosphonic acid are also present in addition to the band at 950 cm -1 assigned to the WdO vibration. 21,22 DFT calculations aimed at describing the vibrational structure of the three species by way of a good agreement with the experimental infrared spectra (Figure 2).…”

Oxidative Degradation of Chitosan to the Low Molecular Water-Soluble Chitosan over Peroxotungstate as Chemical Scissors

“…It indicates that the unit of W(O 2 ) might be the active sites for oxidative degradation of chitosan. In order to prove the above suggestion, Na 2 WO 4 or (NH 4 ) 2 WO 4 with H 2 O 2 which could also form the active W(O 2 ) sites [21] , [25] were used as the catalysts to degrade chitosan. As shown in Figure 4D , the two samples exhibit the degradation ratio of chitosan as high as that of K 2 [W 2 O 3 (O 2 ) 4 ], which is consistent with our suggestion of the W(O 2 ) active sites.…”