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(O-2)(2)L], where L = dipyridyl, o-phenanthroline; M(I)(3)[VO(O-2)(2)(C2O4)];K-2[(nicotinic acid){VO(O-2)(2)}(2)]H2O;M(I)(4)[O{VO(O-2)(2)}2 cystine]2H(2)O; H-4[O{VO(O-2)(2)(adenine)(2))(2)]2H(2)O; and K2H2[O{VO(O-2)(2)(adenosine)}(2)]2H(2)O. Monoperoxo vanadates(V) correspond to the formula M(I)(2)[VO(O-2)L](2) for L = citrate and malate; M(I)(2)[VO(O-2)L] for L = nitrilotriacetate; M(I)[VO(O-2)L] for L = iminodiacetate, tartrate and EDTA; and [HVO2(O-2)(adenosine)]2H(2)O. 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) stretch- ing frequency bands in IR can be correlated with the corresponding bond lengths and the [peroxo similar to 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.