To study the role of the triiodide (I3 )- anion in establishing various halogen bonding patterns, the trimethylphenylammonium iodide (NMe3 PhI) salt was reacted with diiodine (I2 ) in the presence of a series of organoiodines, tetraiodoethylene (TIE), 1,2-diiodo-3,4,5,6-tetrafluorobenzene (o-F4 DIB), 1,4-diiodo-2,3,5,6-tetrafluorobenzene (p-F4 DIB), and 1,3,5-trifluoro-2,4,6-triiodobenzene (1,3,5-F3 I3 B) to form cocrystals of the organoiodines with the trimethylphenylammonium triiodide (NMe3 PhI3 ) salt. Single-crystal X-ray crystallography revealed the (I3 )- anion served as a halogen bond acceptor for the organoiodine donors, forming a variety of 1-D, 2-D, and 3-D packing arrangements through I⋅⋅⋅I halogen bonding. Significant asymmetry was observed within the (I3 )- anion. The melting points of the cocrystalline materials, as determined by simultaneous DSC/TGA, ranged from 43 °C to 119 °C and showed a strong dependence on the identity of the organoiodine incorporated into the crystal lattice.
Keywords: X-ray diffraction; crystal engineering; halogen bonding; polymorphism; triiodide cocrystals.
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