Effect of Cations in Infrared and Computational Analysis of Vanadium-Containing Six-Coordinate Oxotungstates

Abstract

Complex salts of VW5O193-, cis-V2W4O19,4-, and W6O192- anions have been investigated using Fourier transform infrared spectroscopy and density functional theory computational methods. The intensities of the infrared absorption bands commonly used to identify the bridge and terminal oxygen atoms in these hexametalate systems were found to depend drastically on the nature of the countercation and presence of water in the salts. Theoretical investigations suggest that the anions alone may not show significant absorption in the region commonly assigned to the M−Ot vibrations (subscripts t and b denote terminal and bridged oxygen atoms, respectively). At the same time, the addition of even a single molecule of water or tetraalkylammonium into the calculation results in almost quantitative agreement between the theoretical and experimental spectra. The presence of vanadium has a profound effect both on M−Ot and on M−Ob−M vibrations.