The structural landscape of heteroaryl-2-imidazoles: competing halogen- and hydrogen-bond interactions

In order to examine the competition between hydrogen bonds and halogen bonds when confronted with a probe molecule containing multiple potential acceptor sites and one hydrogen-bond donor, five heteroaryl-2-imidazoles were synthesized and subsequently co-crystallized with fifteen different halogen-bond donors. 30 of the 75 experiments resulted in the formation of co-crystals, and fifteen of these produced crystals were suitable for single-crystal X-ray diffraction analysis. A systematic analysis of the primary intermolecular interactions in these fifteen structures shows that the halogen bond is formed with the best acceptor site (as predicted by DFT molecular electrostatic potential surface calculations) demonstrating that a suitably activated iodine-based halogen-bond donor can compete with a strong hydrogen-bond donor in the directed assembly of molecular solid-state architectures.