Long-range supramolecular synthon polymorphism: a case study of two new polymorphic cocrystals of Ph2Te2-1,4-C6F4I2

Along with the reported earlier cocrystal of diphenyl ditelluride (Ph2Te2) and halogen bond donor 1,4-diiodo-tetrafluorobenzene (p-DITFB) 1 alpha, its two new polymorphic forms (1 beta and 1 gamma) present a rare case of long-range supramolecular synthon module polymorphism. In contrast to I center dot center dot center dot Te halogen bonding (HaB) in the earlier reported form 1 alpha, their main building motif is I center dot center dot center dot pi(Ph) HaB. The lattice energy calculations for this polymorphic triad suggest the 1 alpha-1 beta-1 gamma sequence from the kinetic to thermodynamic form. Cocrystal 1 beta appeared completely isostructural with the Ph2Se2 center dot(p-DITFB) cocrystal and the double chains of Ph2Te2 molecules in 1 beta reproduce the packing of the pure Ph2Se2 and the pattern of Ph2Se2 chains in Ph2Se2 center dot p-DITFB. Single chains of Ph2Te2 in the 1 gamma form feature only partial similarity with 1 beta but together, these three polymorphic cocrystals along with the native Ph2Te2 and Ph2Se2 compose a rather detailed and remarkable structural landscape. It suggests the putative polymorphic forms of Ph2Te2 and Ph2Se2, 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 1 beta and 1 gamma and their noticeably different habits.