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 center dot center dot center dot I-C, C-I center dot center dot center dot pi, pi-pi and C-H center dot center dot center dot 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 x 10(3) s(-1) and 0.22 x 10(3) 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.