Structure of methyl 4-(trimethylammonium)benzoate iodide studied by X-ray diffraction, DFT calculations, NMR and FTIR spectra

► Methyl-4-(trimethylammonium)benzoate cations and iodide anions form layers. ► Cations and anions interact electrostatically. ► The structure of the title compound is optimized by the B3LYP/6-311G(d,p) approach. ► The interpretation of IR frequencies is based on the calculated spectrum.