Effects of Halogenation on Quinoline‐Malononitrile‐based AIEgens: Photophysical Properties Investigation and Wash‐Free Imaging

Halogenation plays a critical role on the photophysical performances, including intramolecular charge transfer, molecular interaction in solid, and photobleaching resistance, of the quinoline-malononitrile based aggregation-induced emission luminogens (AIEgens). We demonstrated the halogenated AIEgens showed red-shifted emission, strong fluorescence, and excellent photostability. Further use of them for wash-free imaging was also studied.

Abstract

Developing halogen-functionalized fluorescent dyes with intriguing photophysical properties, including enhanced photostability, is particularly important for bioimaging. In this work, we synthesized two new halogen-functionalized aggregation-induced emission (AIE)-active molecules, DQMF-OH and DQMCl-OH, based on the quinoline-malononitrile chromophore. The halogen effect on the photophysical characteristics was detailedly studied by absorption and fluorescence spectroscopy, density functional theory calculations, and crystal structures. Compared with non-halogen substituted AIE luminogen (AIEgen) DQM-OH, the halogen substituted DQMF-OH and DQMCl-OH exhibited red-shifted absorptions and emissions in the solution and solid state. In addition, DQMF-OH and DQMCl-OH also possessed enhanced fluorescence toward viscosity changes. These AIEgens served as remarkable imaging tools for cell tracking in a wash-free manner. Furthermore, DQMF-OH and DQMCl-OH showed much more excellent photobleaching resistance than DQM-OH. Our work sheds new light on developing fluorescent halogenated dyes with enhanced photophysical performances for biological applications.

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