Developing molecules with high emission efficiency both in solution and the solid state is still a great challenge, since most organic luminogens are either aggregation-caused quenching or aggregation-induced emission molecules. This dilemma was overcome by integrating planar and distorted structures with long alkyl side chains to achieve DAπAD type emitters. A linear diphenyl-diacetylene core and the charge transfer effect ensure considerable planarity of these molecules in the excited state, allowing strong emission in dilute solution (quantum yield up to 98.2 %). On the other hand, intermolecular interactions of two distorted cyanostilbene units restrict molecular vibration and rotation, and long alkyl chains reduce the quenching effect of the π-π stacking to the excimer, eventually leading to strong emission in the solid state (quantum yield up to 60.7 %).
Keywords: bioimaging; luminescence; molecular engineering; molecular stacking; noncovalent interactions.
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