Peroxovanadium(V) complexes of glycolic acid as studied by NMR spectroscopy

• Author(s): Justino, Licínia L. G. ; Ramos, M. Luísa ; Caldeira, M. Madalena ; Gil, Victor M. S.
• Date: 2000
• Persistent ID: http://hdl.handle.net/10316/5233
• Origin: Estudo Geral - Universidade de Coimbra
• Subject(s): Peroxovanadium(V) complexes; Glycolic acid; Multinuclear NMR
• Document Type: Article
• Language: English

Description

Multinuclear (1H, 13C, 17O, 51V) 1D and 2D NMR spectroscopy has been used to characterize the peroxovanadium(V) complexes of glycolic acid in aqueous solution. One 2:2:2 (metal:ligand:peroxo) complex, together with a 1:1:1 and a 2:2:1 species, are found in the pH range 1-7. The 2:2:2 complex is a monoperoxo (one peroxide unit per vanadium atom) dinuclear species having a V2O3 4+ seven-coordinated metal centre. In this structure, the two vanadium atoms are triple bridged, two of those bridges being formed by oxygen atoms of the hydroxyl group of the acid. The 1:1:1 species has a seven-coordinated VO3+ metal centre. Glycolic acid bonds to the vanadium atoms in a bidentate way, through both the carboxylic and the hydroxyl groups. The peroxo groups are bound in the equatorial plane relative to the apical V=O and the geometry around each vanadium atom is close to pentagonal bipyramidal. The 2:2:1 complex is similar to the 2:2:2 species, except for one of the vanadium centres, which is now a five-coordinated oxovanadium centre. Three additional complexes are found in very small amounts for some pH and concentration conditions. Further support for the proposal of monoperoxovanadium species is given by UV-visible spectroscopy results. http://www.sciencedirect.com/science/article/B6TG5-428111H-J/1/b102dece7ebb3928c267e236534a1c50