Halogen-bonded liquid-crystalline complexes formed from 4-alkoxyphenylpyridines with iodine and with interhalogens

Strongly halogen-bonded complexes are formed between 4-alkoxyphenyl-4-pyridines and iodine as well as the interhalogen compounds ICl and IBr, and examples of each are characterised by single crystal X-ray crystallography. On heating, all but one of the complexes display a liquid-crystalline smectic A phase, although there is evidence of decomposition as the materials are heated through the mesophase. For such short molecules, the mesophases are rather stable and small-angle X-ray scattering shows that the complexes form a type of antiparallel, head-to-head dimeric arrangement in the mesophase. Quantum chemical calculations at the DFT (M06-2X) and MP2 levels of theory show the complexes to have very high dipole moments (between approximate to 9-12 D) and the mesophase stability of the complexes is rationalised in terms of antiparallel correlations induced by the strong molecular dipoles.

Automated summary

Strongly halogen-bonded complexes between 4-alkoxyphenyl-4-pyridines and iodine, ICl, and IBr were studied using single crystal X-ray crystallography. The complexes exhibited a liquid-crystalline smectic A phase upon heating, although decomposition was observed. Small-angle X-ray scattering revealed that the complexes formed an antiparallel, head-to-head dimeric arrangement in the mesophase. Quantum chemical calculations demonstrated that the complexes had high dipole moments and the mesophase stability was attributed to antiparallel correlations induced by the strong molecular dipoles.