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

The crystal structure of the new iodobismuthate (PyPy)₂(PyPyH)₂Bi₆I₂₆ was found to consist of unusual hexanuclear [Bi₆I₂₆]⁶⁻ anions containing the linear I₄²⁻ 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 ± 2kcalmol⁻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.