Halogen-Bonded Supramolecular Parallelograms: From Self-Complementary Iodoalkyne Halogen-Bonded Dimers to 1:1 and 2:2 Iodoalkyne Halogen-Bonded Cocrystals

The formation of supramolecular parallelograms utilizing iodoalkyne–pyridine halogen bonding is described. The crystal structures of four iodoalkynyl-substituted (phenylethynyl)pyridines demonstrate the feasibility of discrete self-complementary dimer formation. These compounds 3-(2-iodoethynyl-phenylethynyl) pyridine (1), 2-(3-iodoethynyl-phenylethynyl) pyridine (2), 3-(4,5-difluoro-2-iodoethynyl-phenylethynyl) pyridine (3), and 2-(5-iodoethynyl-2,4-dimethylphenylethynyl) pyridine (4) all form parallelogram-shaped dimers with two self-complementary short N–I halogen bonds. The potential formation of iodoalkynyl halogen-bonded supramolecular macrocycles is demonstrated by the formation of a discrete halogen-bonded parallelogram-shaped complex in the 1:1 cocrystal formed from the bis iodoalkyne, 1-iodoethynyl-2-(3-iodoethynyl-phenylethynyl)-4,5-dimethoxybenzene (6), and the dipyridyl, 5-phenyl-2-(pyridin-3-ylethynyl)pyridine (7). Furthermore, discrete supramolecular parallelograms form within the 2:2 cocrystal formed between 1,2-bis(iodoethynyl)-4,5-difluorobenzene and the dipyridyl 4-(3-pyridylethynyl) pyridine (8).