Copper(II) and oxovanadium(IV) complexes of 2,3-dihydroxyterephthalic and 2,3,4-trihydroxybenzoic acids.

The complexes formed by 2,3-dihydroxyterephthalic and 2,3,4-trihydroxybenzoic acids with copper(II) and oxovanadium(IV) in aqueous solution were studied by spectroscopic and potentiometric techniques. The results show that all of the functional groups of the ligands are involved in complex formation. Rather stable di- and tri- or tetra-meric species were detected with both metal ions. While the former are EPR-silent, the latter could be characterised by EPR spectroscopy.