Long-range supramolecular synthon polymorphism: a case study of two new polymorphic cocrystals of PhTe-1,4-CFI

Along with the reported earlier cocrystal of diphenyl ditelluride (Ph 2 Te 2 ) and halogen bond donor 1,4-diiodo-tetrafluorobenzene ( p -DITFB) 1α , its two new polymorphic forms ( 1β and 1γ ) present a rare case of long-range supramolecular synthon module polymorphism. In contrast to I Te halogen bonding (HaB) in the earlier reported form 1α , their main building motif is I π(Ph) HaB. The lattice energy calculations for this polymorphic triad suggest the 1α - 1β - 1γ sequence from the kinetic to thermodynamic form. Cocrystal 1β appeared completely isostructural with the Ph 2 Se 2 ·( p -DITFB) cocrystal and the double chains of Ph 2 Te 2 molecules in 1β reproduce the packing of the pure Ph 2 Se 2 and the pattern of Ph 2 Se 2 chains in Ph 2 Se 2 · p -DITFB. Single chains of Ph 2 Te 2 in the 1γ form feature only partial similarity with 1β but together, these three polymorphic cocrystals along with the native Ph 2 Te 2 and Ph 2 Se 2 compose a rather detailed and remarkable structural landscape. It suggests the putative polymorphic forms of Ph 2 Te 2 and Ph 2 Se 2 , which were studied in silico by periodic DFT. The energy framework approach appeared to be a useful and illustrative way to analyze the correlation between the energetic structure of co-crystals 1β and 1γ and their noticeably different habits. Two new polymorphic forms of Ph 2 Te 2 -1,4-C 6 F 4 I 2 cocrystals feature an unusual packing of Ph 2 Te 2 molecules, which is typical for native Ph 2 Se 2 but not Ph 2 Te 2 . This suggests the existence the yet unknown, Ph 2 Se 2 -like polymorph of Ph 2 Te 2 .