Influence of Secondary Interactions on Structural Diversity between a Pair of Halogen-Bonded Co-Crystals Containing Isosteric Donors

The formation of a pair of co-crystals based upon isosteric halogen-bond donors, namely 1,4-diiodoperchlorobenzene and iodoperchlorobenzene, along with the acceptor 4,4-bipyridine is reported. As expected, the components in each co-crystal engage in halogen bonding interactions resulting in a one-dimensional chain-like structure. In particular, the co-crystal containing 1,4-diiodoperchlorobenzene is primarily held together by I···N halogen bonds while the solid based upon iodoperchlorobenzene forms both I···N and Cl···N interactions. Structural diversity is achieved between these co-crystals based upon the type of secondary interactions involving the chlorine atoms on each halogen-bond donor even though they are isosteric in nature.