A study of hierarchy of hydrogen and halogen bonds in the molecular complexes of 4-iodophenol with various aza-donor compounds

Abstract

Molecular complexes of 4-iodophenol, 1 with various aza-donor compounds, 4,4?-bipyridine (a), 1,3-bis(4-pyridyl)propane (b), 4,4?-azopyridine (c), 1,10-phenanthroline (d), phenazine (e), 1,4-diazabicyclo [2.2.2]octane (DABCO)(f), 1,2-bis(4-pyridyl)ethene (g) and 1,2-bis(4-pyridyl)ethane (h), have been prepared by co-crystallization. All the complexes were analysed by single crystal X-ray diffraction technique. Amongst, in the complexes, 1a, 1b and 1c, each di-acceptor moiety is connected to two molecules of phenol, 1 through a hydrogen (O[sbnd]H?N) and a halogen bond (I?N), while in the complexes 1c?,1d � 1f, the constituents recognise each other only through O[sbnd]H?N hydrogen bonds. However, in the complexes of 1g and 1h, both the halo and hydrogen interactions express themselves exclusively as well as independently within the same crystals. An analysis of hierarchy of O[sbnd]H?N and I?N non-covalent interactions suggests that both hydrogen and halogen bonds are realized equally with diacceptor aza-compounds with twisted conformation, while in the complexes with planar diacceptor moieties either hydrogen or halogen bonds show equal propensity independently. This analysis is supported by Hirshfeld surface analysis of the diacceptors of the co-crystals. � 2016