Crystal supramolecularity of organic–inorganic hybrids of polyhalides: structures of 2,5-dibromopyrazinium triiodide and 2-bromopyridinium dibromoiodide

Abstract

Crystal structure determinations of the compounds (C₄H₄Br₂N₂)⁺[I₃]⁻, 1, and (C₅H₅BrN)⁺[IBr₂]⁻, 2, have been carried out. In 1, the anion is surrounded symmetrically by four cations. This arrangement results from both (π)N–H ··· I–I–I and I–I–I ··· Br–C(π) intermolecular interactions, tying the cations and anion into sheets of pseudo four fold arrays of cations and anions. The crystal lattice of 2 consists of stacks of cations and anions that are connected via C–Br ··· Br–I–Br, N–H ··· Br–I–Br, and Br–I–Br ··· IBr₂ inter-stacks intermolecular interactions leading to a supramolecular assembled lattice. The IBr₂⁻ anions are also assembled in a nearly T-shaped dimeric motif where one bromide end is interacting with the central iodide atom in another IBr₂⁻ unit (I–Br ··· I angle of 154°). The extensive anion ··· cation intermolecular interactions in both compounds lead to a crystal supramolecularity.