Structural Equivalence of Br and I Halogen Bonds: A Route to Isostructural Materials with Controllable Properties

The structural equivalence of halogen-bonded iodine and bromine functionalities has been systematically explored as a general tool to construct isostructural cocrystal architectures with differing strengths of the constituent halogen bonds. By using acridine and phenazine as halogen bond acceptors, the structural equivalence of Br and I donors was tested for cocrystals based on discrete (0-dimensional) or infinite (1-dimensional chain) supramolecular topologies. In addition to being robust to changes in the topology of halogen-bonded assembly, this structural equivalence was also persistent in the presence of weak intermolecular hydrogen bonding of C−H···N type. The potential application of structurally equivalent I and Br donors in the design of molecular materials is illustrated by constructing pairs of solids that exhibit differing melting point, stability, and crystal morphology, although based on identical halogen-bonded architectures.