... figure Scheme 3. Structures of the Strong Halogen Bond Donors. In crystalline NIS,(88) a short N–I···O═C XB is indeed found (2.58 Å, 26 ... state, a continuous evolution from cocrystal to salt, with an iodine shift analogous to a proton shift, according to the equation: A–I···B ⇆ [A] − ···I ...