Issue 12, 2004

Vanadium(iv,v) complexes of d-saccharic and mucic acids in aqueous solution

Abstract

The vanadium(IV,V) complexes formed with two aldaric acids (D-saccharic or D-glucaric acid, and mucic or galactaric acid) in aqueous solution were characterised by employing pH-potentiometry, EPR, multinuclear NMR and UV-VIS spectroscopy. The stoichiometry and stability constants of the complexes formed were determined at 25 °C and ionic strength I = 0.2 mol dm−3 (KCl). The spectral measurements revealed that vanadium(IV,V) coordinates first at the terminal COO functions, forming mononuclear complexes. At pH > 3, through the metal ion-induced deprotonation and coordination of the neighbouring alcoholic functions, (COO, O) coordinated dinuclear complexes are formed, which predominate in the pH range 4–8. In the basic pH range, the ligand molecules are displaced and binary metal hydroxo and oxo complexes are present. EPR measurements at room temperature and at 140 K proved that formation of the VO(IV) dimers is more enhanced at room temperature, but at 140 K their dissociation is favoured. An interesting pH-dependent cis–trans isomeric equilibrium was assumed and analysed by EPR and molecular modelling in the case of the complexes [(VO)2L2Hx] (x = −2 and −4). Joint evaluation of the pH-potentiometric and 51V NMR measurements revealed that both aldaric acids are able to bind an excess of vanadium(V), through the formation of oligomeric 2 ∶ 1 and 3 ∶ 2 species, besides the 2 ∶ 2 species formed with VO(IV).

Graphical abstract: Vanadium(iv,v) complexes of d-saccharic and mucic acids in aqueous solution

Article information

Article type
Paper
Submitted
30 Jan 2004
Accepted
11 May 2004
First published
25 May 2004

Dalton Trans., 2004, 1882-1891

Vanadium(IV,V) complexes of D-saccharic and mucic acids in aqueous solution

Á. Dörnyei, E. Garribba, T. Jakusch, P. Forgó, G. Micera and T. Kiss, Dalton Trans., 2004, 1882 DOI: 10.1039/B401443J

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