Structural and Chemical Effects of the Surrounding Cations and Coexisting Compounds on [M(α-PW(11)O(39))(2)](n–)

[Image: see text] The effects of countercations and coexisting compounds on the molecular structure of the [M(α-PW(11)O(39))(2)](n−) polyanion were analyzed in terms of the repulsion and twisting of two [α-PW(11)O(39)](7–) units. More specifically, it was found that two [α-PW(11)O(39)](7–) ions approached one another upon reducing the ionic radius of M in [M(α-PW(11)O(39))(2)](n−). The interactive twisting of the [α-PW(11)O(39)](7–) units prevented mutual repulsion of the units containing terminal O atoms, and the tendency for approach and twisting of the [α-PW(11)O(39)](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-PW(11)O(39))(2)](n−) determined the molecular conformation and the isolated form of the polyanion.