Peroxo heteroligand vanadates(V): synthesis, spectra-structure relationships, and stability toward decomposition.

Effect of heteroligands (L) on the properties of vanadium peroxides was investigated by preparing a number of peroxovanadium complexes, which were characterized by analysis, IR, UV/V and NMR spectra. X-ray structures for some were obtained. The vanadates(V) contain the cation M(I) = Na, K, NH4, Rb or Cs. Diperoxo complexes include M(I)[VO(O2)2 L], where L = dipyridyl, o-phenanthroline; M(I)3[VO(O2)2(C2O4)]; K2[(nicotinic acid)[VO(O2)2]2]H2O;M(I)4[O[VO(O2)2]2cystine]2H2O; H4[O[VO(O2)2(adenine)2)2]2H2O; and K2H2[O[VO(O2)2(adenosine)]2] 2H2O. Monoperoxo vanadates(V) correspond to the formula M(I)2[VO(O2)L]2 for L = citrate and malate; M(I)2[VO(O2)L] for L = nitrilotriacetate; M(I)[VO(O2)L] for L = iminodiacetate, tartrate and EDTA; and [HVO2(O2)(adenosine)]2H2O. Syntheses of these heteroligand peroxovanadium compounds are sensitive to pH, temperature and the concentration of the components. The stability towards decomposition in solid state, mother-liquid and pure water solutions depends upon the heteroligand. Characteristic (V = O) and (O-O) stretching frequency bands in IR can be correlated with the corresponding bond lengths and the [peroxo approximately V(V)] charge transfer bands in UV/V spectra. Intramolecular one-electron transfer in peroxo vanadates(V) can trigger the generation of radicals, and its dependency upon the nature of the heteroligand is discussed.

Antitumor activity and toxicity of peroxo heteroligand vanadates(V) in relation to biochemistry of vanadium.

A selected set of 14 V(V) complexes was tested for toxicity and antitumor activity against L1210 murine leukemia, to examine the biological properties of peroxoheteroligand vanadates(V) of the formula (NH4)4[O(VO(O2)2)2], M3I[VO(O2)2C2O4], and MI[VO(O2)L], L = malate, citrate, iminodiacetate, nitrilotriacetate, and EDTA. The x-ray structure is known for five of these compounds. A relationship has been found between the chemical composition and the biological activity (antitumor activity-toxicity) of these complexes. Activity in the L1210 system is defined as greater than or equal to 25% increase in life span, and this was seen with (NH4)4[O(VO(O2)2)2]; M3[VO(O2)2(C2O4)]2H2O, M = K, NH4; and NH4[VO(O2)Malato]H2O. These observations are important for the biochemistry of vanadium. The special nature of electron transfer within the V(V)-peroxo moiety is proposed to be responsible for this phenomenon. Peroxo heteroligand vanadates(V) therefore represent a model system for studying some biochemical interactions of vanadium in living matter.