Cocrystals assembled by pyrene and 1,2- or 1,4-diiodotetrafluorobenzenes and their phosphorescent behaviors modulated by local molecular environment

Two supramolecular cocrystals, 1, pyrene/1,4-diiodotetrafluorobenzene (1,4-DITFB), and 2, pyrene/1,2-diiodotetrafluorobenzene (1,2-DITFB), have been prepared and characterized using X-ray diffraction analysis and multiple spectroscopic methods. Several intermolecular interactions such as C–I⋯I–C, C–I⋯π, π–π and C–H⋯F were observed in cocrystal 1 and/or 2, in which DITFB molecules act simultaneously as an isolator to prevent the pyrene molecule from aggregating and also as a heavy atom effect agent to induce phosphorescence emission from pyrene. The spectral results demonstrate that the two cocrystals both display strong phosphorescence at room temperature with decay rates of 1.7 × 103 s−1 and 0.22 × 103 s−1, respectively. The differences in the phosphorescence behavior between 1 and 2 are relevant to the local molecular environment created by 1,4- or 1,2-DITFB in cocrystals.