Hybrid iodobismuthates code: adapting the geometry of Bi polyhedra to weak interactions.

[Display omitted] The crystal structure of the new iodobismuthate (PyPy) 2 (PyPyH) 2 Bi 6 I 26 was found to consist of unusual hexanuclear [Bi 6 I 26 ]6− anions containing the linear I 4 2− unit, and the experimental Bi–I bond lengths in this anion were used to obtain the relationship between bond length and bond energy. A statistical analysis of 229 crystal structures of iodobismuthates, based on the quantum chemically estimated strength of Bi–I bonds, revealed that the total energy of the Bi3+ polyhedron remains virtually constant at 64 ± 2 kcal mol−1, regardless of its geometry within this family of materials. Thus, the polyhedron geometry flexibly adapts to the relatively weak interactions between iodobismuthate anions and embedded cations. [ABSTRACT FROM AUTHOR]