Phosphorescent co-crystal assembled by 1,4-diiodotetrafluorobenzene with carbazole based on C–I⋯π halogen bonding

Abstract

1,4-diiodotetrafluorobenzene (1,4-DITFB) is an excellent halogen bonding donor and is used to assemble an organic phosphorescent co-crystal with carbazole in which 1,4-DITFB is expected to act as a functional synthon, the cement to link carbazole molecules by halogen bonding and heavy atom perturber to enhance phosphorescence of the emitter carbazole by spin–orbital coupling. The XRD reveals that the stoichiometry of (2 : 1) between 1,4-DITFB and carbazole occurs. An infinite chain is constructed by the C–I⋯π halogen bonding and the π⋯π stacking of edge to edge between two 1,4-DITFB molecules is significant in maintaining stability of the 1D infinite chain. The inter-chain bonding includes C–H⋯I hydrogen bonding, H⋯F or F⋯F contacts to extend the infinite chain to 3D structure. The calculated halogen bonding energy is ca. 23.0 kJ mol⁻¹ based on the single crystal structure, indicating a strong halogen bonding. The co-crystal also is well characterized by powder XRD, FT-IR, Raman, and solid ¹⁹F NMR spectroscopy. Moreover, the co-crystal as suspension microparticles can be very easily assembled in water by dropping water into an ethanol solution of 1,4-DITFB and carbazole. The C–I⋯π halogen bonding of 1,4-DITFB with carbazole should be instructive to develop some phosphorescent nano- or micro-materials.