Halogen-Bonding Complexes Based on Bis(iodoethynyl)benzene Units: A New Versatile Route to Supramolecular Materials

Iodoalkynes [1,4-bis­(iodoethynyl)­benzene (p-BIB) and 1,3-bis­(iodoethynyl)­benzene (m-BIB)] have been used successfully to prepare halogen bonding complexes with a range of 4-pyridine derivatives showing liquid crystalline organizations. The trimeric halogen-bonded complexes obtained from p-BIB have a rod-like structure and exhibited high order calamitic phases (SmB and G). In contrast, m-BIB gives rise to bent-shaped structures that display SmAP-like mesophases. Furthermore it was found that the presence of three and five aromatic rings in these halogen-bonding complexes promotes calamitic mesophases while seven rings are required to stabilize bent-core mesophases. The formation of halogen bonding in the complexes was confirmed by several techniques, including FT-IR, XPS, and single crystal X-ray diffraction and the strength of the bonds was evaluated by DFT calculations