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

Abstract

Along with the reported earlier cocrystal of diphenyl ditelluride (Ph₂Te₂) 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 Ph₂Se₂·(p-DITFB) cocrystal and the double chains of Ph₂Te₂ molecules in 1β reproduce the packing of the pure Ph₂Se₂ and the pattern of Ph₂Se₂ chains in Ph₂Se₂·p-DITFB. Single chains of Ph₂Te₂ in the 1γ form feature only partial similarity with 1β 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 1β and 1γ and their noticeably different habits.