Overlooked Solid State Structure of 1,3-I₂C₆F₄—The Meta-Member of an Iconic Halogen Bond Donors Trio

The solid-state structure of the meta-isomer of diiodotetrafluorobenzene (DITFB), the sole liquid DITFB at 25 °C, is reported. Computational and comparative analyses of its crystal packing have elucidated potential factors contributing to its lower melting point and reduced affinity as a halogen bond donor conformer as compared to the para-isomer. This discussion also addresses the lower melting points of ortho- and meta-isomers in general. The platelet crystal habit of 1,3-DITFB is examined in relation to its energy framework pattern, proposing a comprehensive and illustrative predictive model for its faster growth in the [001] direction. This growth aligns with the maximum attachment energy.