Structural and Chemical Effects of the Surrounding Cations and Coexisting Compounds on [M(alpha-PW11O39)2]n-

The effects of countercations and coexisting com-pounds on the molecular structure of the [M(alpha-PW11O39)2]n- polyanion were analyzed in terms of the repulsion and twisting of two [alpha-PW11O39]7- units. More specifically, it was found that two [alpha-PW11O39]7- ions approached one another upon reducing the ionic radius of M in [M(alpha-PW11O39)2]n-. The interactive twisting of the [alpha-PW11O39]7- units prevented mutual repulsion of the units containing terminal O atoms, and the tendency for approach and twisting of the [alpha-PW11O39]7- units varied as a function of the type of countercation and the presence of coexisting compounds. Overall, this study demonstrated that some interactions between the counteraction and coexisting compounds with [M(alpha-PW11O39)2]n- determined the molecular conformation and the isolated form of the polyanion.