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This article reports the enhanced photoluminescent properties observed in the crystals of a cube-plane-cube shape amphiphile composed of perylene diimide (PDI) tethered with polyhedral oligomeric silsesquioxanes (POSS) at the imide position via either rigid or flexible linkages (POSS-PDI-POSS). The fluorescence quantum yields (Φf) of the conjugates in crystal (∼0.48) are much higher than that of the more amorphous samples (∼0.17) and that of the reference compound without pendant POSS cage (∼0.12). The enhancement was understood in three ways. First, their self-assembly behaviors in gaseous phase were studied by tandem mass spectrometry coupled with traveling wave ion mobility separation; second, their self-assembly behaviors in solution were revealed by concentration- and solvent-dependent experiments using UV/vis absorption and fluorescence spectrometry; and third, the molecular packing in crystals was determined by wide angle X-ray diffraction and transmission electron microscope. The results demonstrate the conjugates' strong tendency toward dimer formation in solution and show a unique molecular packing of discrete dimeric motifs in the solid states. It suggests that the high Φf of these conjugates can be attributed to the discontinuous π–π stacking, which results in a weaker electron interaction between the dimers, and the relatively fixed position of the PDI, which prohibits the common structural relaxation of PDIs π-planes.
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Citation / Publisher Attribution
RSC Advances, v. 7, p. 6530-6537
Scholar Commons Citation
Shao, Yu; Yin, Guang-Zhong; Ren, Xiangkui; Zhang, Xinlin; Wang, Jing; Guo, Kai; Li, Xiaopeng; Wesdemiotis, Chrys; Zhang, Wen-Bin; Yang, Shuguang; Zhu, Meifang; and Sun, Bin, "Engineering π–π Interactions for Enhanced Photoluminescent Properties: Unique Discrete Dimeric Packing of Perylene Diimides" (2017). Chemistry Faculty Publications. 122.