The formation of ternary complexes between VO(maltolate)2 and small biologands.

In order to assess the solution state of VO(IV) in organisms when administered in the form of the bis(maltolato) complex (VO(malt)2), ternary systems of VO(IV)--maltol with various bioligands (potential metal ion binders of biofluids and tissues), such as inorganic phosphates, adenosine nucleotides, catechol derivatives, citrate and oxalate, were studied. The speciation of VO(IV) in these ternary systems was studied by pH-potentiometry, while the binding modes of the complexes were determined by spectral (UV--Vis and electron paramagnetic resonance) methods. The results support strongly the assumption that VO(malt)2 undergoes transformation into mixed ligand complexes formed with the various VO(IV) binders of biological fluids and tissues.