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The K3PW12O40, K2.5H0.5PW12O40, K2HPW12O40, KH2PW12O40, Ag3PW12O40 and Tl3PW12O40 salts were synthesized and characterized by thermal analysis, IR and impedance spectroscopy, and SEM. The physicochemical characterization of acid alkaline salts revealed the presence of biphasic mixtures of unreacted heteropoly acid and its neutral salt. The unreacted heteroply acid could be washed away by treating the acid salt with water.

On the basis of previously recorded Raman and IR spectral data on different crystallohydrates of alkaline-earth 12-tungstophosphoric acid salts (obtained from mother solution and those kept under constant relative humidity (RH) of 35%), an effort was made to determine the position of cations in the Keggin unit. Shifts or band splitting in vibrational spectra of the salts, as well as the changes in band intensities were found to be connected to the cation properties. The spectral data also demonstrated a great influence of cation properties on the secondary structure of Keggin anions and dynamics of protonic species.

In our previous work we investigated the conductivity and dielectric relaxation phenomena in heteropoly acids and their salts. In this work, we have studied the conductivity of grains and grain boundaries in compressed powders of 12-tungstophosphoric acid (WPA) salts with univalent and bivalent ions. The method of impedance spectroscopy has been employed in the frequency range from 5 Hz to 500 kHz. We obtained grains and grain boundaries conductivities as well as corresponding activation energies. Grain conductivity in all investigated salts is always higher than the grain boundary conductivity.

It is known that various polyoxovanadates interact specifically with enzymes, which is the main way of their biochemical activity. Therefore we have synthesized ammonium decavanadate, (NH4)6V10O28·6H2O. The novel compound was characterized by elemental and thermal analysis, X-ray powder and single crystal diffraction and IR and Raman spectroscopy. Its conductive properties have been studied, too. The spectroscopic analysis has shown the presence of hydrogen bonds of different strengths. In order to improve the biochemical activity of this compound and having in mind the presence of strong hydrogen bonds, we essayed the synthesis of complex of polyoxovanadate with alanine. The obtained product was characterized by the mentioned methods.

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