α,ω-diiodoperfluoroalkanes having different numbers of difluoromethylene groups self-assemble with the halides of α,ω-diammonium (and -diphosphonium) alkanes having different numbers of methylene groups. Solid and crystalline supramolecular adducts are obtained for many possible pairings of alkyl and perfluoroalkyl chains lengths. Some predictive rules will be formulated in order to identfy the specific diiodoperfluoroalkane required for the selective involvement in the cocrystal formation of a given bis-onium cation.