Cocrystals with tunable luminescence colour self-assembled by a predictable method

Abstract

Organic light-emitting materials play an essential role in the field of luminescent materials because they are easily prepared and they have controllable luminescent properties. Here it is shown that intermolecular interactions and luminescent properties of cocrystals can be predicted using the molecular surface electrostatic potential of selected π-hole/σ-hole...π bonding donor haloperfluorobenzenes and acceptor acenaphthene (AC). Single-crystal X-ray diffraction data reveal that actual bonding patterns in five cocrystals assembled from haloperfluorobenzenes and AC are in accordance with predictable patterns of intermolecular interactions; that is π-hole...π bond is the major interaction in AC–octafluoronaphthalene, AC–1,4-dibromotetrafluorobenzene and AC–1,3,5-tribromo-2,4,6-trifluorobenzene cocrystals, whereas σ-hole...π bond is the major interaction in AC–1,4-diiodotetrafluorobenzene and AC–1,3,5-trifluoro-2,4,6-triiodobenzene cocrystals. The luminescent properties of the cocrystals are affected by the bonding patterns between AC and haloperfluorobenzenes; the π-hole...π bond leads to weak phosphorescence, whereas the σ-hole...π bond results in weak delayed fluorescence and relatively strong phosphorescence.