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

The effects of countercations and coexisting compounds on the molecular structure of the [M(α-PW11O39)2]n− polyanion were analyzed in terms of the repulsion and twisting of two [α-PW11O39]7– units. More specifically, it was found that two [α-PW11O39]7– ions approached one another upon reducing the ionic radius of M in [M(α-PW11O39)2]n−. The interactive twisting of the [α-PW11O39]7– units prevented mutual repulsion of the units containing terminal O atoms, and the tendency for approach and twisting of the [α-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(α-PW11O39)2]n− determined the molecular conformation and the isolated form of the polyanion.