Halogen and Hydrogen Bond Motifs in Ionic Cocrystals Derived from 3-Halopyridinium Halogenides and Perfluorinated Iodobenzenes

Four halopyridinium salts, 3-chloro- and 3-bromopyridinium chlorides and bromides, have been successfully cocrystallized with two ditopic perfluorinated iodobenzenes, 1,4-diiodotetrafluorobenzene and 1,2-diiodotetrafluorobenzene. These halogen bond donor molecules were chosen because the different positionings of halogen bond donor atoms can lead to different supramolecular architectures. In this work, we present insight into the halogen bond acceptor potential of chloride and bromide ions, as well as the halogen bond donor potential of chlorine and bromine atoms substituted on the pyridinium ring when combined with the expectedly very strong hydrogen bonds between halopyridinium ions and free halogenide anions. A series of eight cocrystals were obtained in which three pairs of isostructural cocrystals were formed. Dominant interactions in the obtained cocrystals were charge-assisted hydrogen bonds between halopyridinium cations and halogenide ions as well as halogen bonds between halogen atoms on the pyridinium ring and halogenide ions.

Crystal data and refinement details for the prepared cocrystals. 8 Figure S1. Molecular structure of (ClpyHCl)(14tfib) showing the atom-labeling scheme. Displacement ellipsoids are drawn at the 50 % probability level, and H atoms are shown as small spheres of arbitrary radius.
12 Figure S2. Molecular structure of (ClpyHCl) 2 (12tfib) showing the atom-labeling scheme. Displacement ellipsoids are drawn at the 50 % probability level, and H atoms are shown as small spheres of arbitrary radius.
12 Figure S3. Molecular structure of (ClpyHBr) 2 (14tfib) showing the atom-labeling scheme. Displacement ellipsoids are drawn at the 50 % probability level, and H atoms are shown as small spheres of arbitrary radius.
13 Figure S4. Molecular structure of (ClpyHBr) 2 (12tfib) showing the atom-labeling scheme. Displacement ellipsoids are drawn at the 50 % probability level, and H atoms are shown as small spheres of arbitrary radius.
13 Figure S5. Molecular structure of (BrpyHCl)(14tfib) showing the atom-labeling scheme. Displacement ellipsoids are drawn at the 50 % probability level, and H atoms are shown as small spheres of arbitrary radius.
14 Figure S6. Molecular structure of (BrpyHCl) 2 (12tfib) showing the atom-labeling scheme. Displacement ellipsoids are drawn at the 50 % probability level, and H atoms are shown as small spheres of arbitrary radius.
14 Figure S7. Molecular structure of (BrpyHBr) 2 (14tfib) showing the atom-labeling scheme. Displacement ellipsoids are drawn at the 50 % probability level, and H atoms are shown as small spheres of arbitrary radius.
15 Figure S8. Molecular structure of (BrpyHBr)(12tfib) 2 showing the atom-labeling scheme. Displacement ellipsoids are drawn at the 50 % probability level, and H atoms are shown as small spheres of arbitrary radius.
15 Figure S9. Comparison of powder patterns generated from single crystal data for isostructural cocrystals.

SINGLE-CRYSTAL X-RAY DIFFRACTION EXPERIMENTS
The crystal and molecular structures of the prepared cocrystals were determined by single crystal X-ray diffraction. Details of data collection and crystal structure refinement are listed in Table S1, S2, S3 and S4. Diffraction measurements were made on an Oxford Diffraction Xcalibur Kappa CCD X-ray diffractometer and Rigaku Synergy XtaLAB X-ray diffractometer with graphite-monochromated MoK ( = 0.71073Å) radiation. The data sets were collected using the  scan mode over the 2 range up to 54° (Xcalibur Kappa CCD) and up to 64° (Synergy XtaLAB). Programs CrysAlis CCD, CrysAlis RED and CrysAlisPro were employed for data collection, cell refinement, and data reduction. 3,4 The structures were solved by direct methods and refined using the SHELXS, SHELXT, and SHELXL programs, respectively. 5, 6 The structural refinement was performed on F 2 using all data. Hydrogen atoms were placed in calculated positions and treated as riding on their parent atoms. Single crystal diffraction data for (ClpyHCl)(14tfib), (BrpyHCl)(14tfib) and (ClpyHBr) 2 (14tfib) salt cocrystals was treated during data reduction as resulting from a combination of two twin components. All calculations were performed using the WINGX crystallographic suite of