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 ).