The structure of tetra-n-butyl ammonium iodide consists of a positively charged tetra-n-butyl ammonium cation (TBA+) and a negatively charged iodide anion (I-). The tetra-n-butyl ammonium cation has four n-butyl groups attached to a central nitrogen atom, giving it a bulky and hydrophobic character. The iodide anion is a spherical, relatively large anion with a high polarizability. In the solid state, tetra-n-butyl ammonium iodide exists as a crystalline salt, where the TBA+ and I- ions are arranged in a regular lattice structure. In solution, the salt dissociates into its constituent ions, which can move freely and interact with other species present.