Abstract Halide-anion binding to 1, 12-dodecanediammonium, tetramethyl-1, 12- dodecanediammmonium, and tetramethyl-1, 7-heptanediammonium has been investigated with infrared multiple-photon dissociation (IRMPD) spectroscopy in the 1000–2250 cm− 1 spectral region and with theory. Both charged ammonium groups in these diammonium compounds interact with the halide anion resulting in an ionic hydrogen bond (IHB) ...