Interplay between Hydrogen and Halogen Bonding in Cocrystals of Dipyridinylmethyl Oxalamides and Tetrafluorodiiodobenzenes

Herein, we examine how the combination of multiple intermolecular interactions influences the supramolecular assembly of dipyridinylmethyl oxalamides and tetrafluorodiiodobenzenes into distinct well-defined nanostructures. A series of 6 regioisomers were selected and crystallized resulting in 11 cocrystals and 1 cocrystal solvate. Three halogen- and hydrogen-bonded supramolecular macrocycles were observed, two of which form large enough channels to accommodate disordered guest molecules. In another case, packing of infinite chains formed columnar channels, which were occupied with stacks of the halogenated coformers. Molecular electrostatic potential surfaces were calculated to qualitatively rank each binding site in order to make inferences about the expected assembly patterns. Although the oxalamide oxygen was not always predicted to be the best acceptor, self-association of this building block satisfies two donors and two acceptors and was primarily observed. Further N···I halogen-bonding interactions formed from pyridyl acceptors and halobenzene donors. Simple electrostatic potential calculations prove to be practical guidelines for predicting the outcome of multiple component crystallizations. But when cooperative directing units, such as oxalamides are employed, additional factors including the number and proximity of functional groups as well as geometric constraints appear to be necessary.