Hybrid of Indolizine and Merocyanine—A New Class of Organelle-Specific Dyes
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AngewChemIntEd_2025_e202508044.pdf (1.27 MB)
0000-0001-5475-7867 Date
2025
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Wiley-VCH GmbH
Abstract
Unlocking the potential of electron-rich 2-hydroxyindolizines led to the discovery of a new class of dyes—indolizine-merocyanines (IndMer) and indolizine-cyanines. Tandem Friedel–Crafts alkylation followed by intramolecular nucleophilic aromatic substitution afforded structurally diverse dyes, as both the nucleophilic and electrophilic partners can be broadly modified. A convergent fragment coupling strategy allowed rapid access to these π-conjugated merocyanines in three steps from pyridines. Uniform distribution of the HOMO and LUMO combined with negligible change of dipole moment upon excitation is responsible for the intense orange or red emission of this new family of reasonably photostable dyes in a broad range of solvents. The new merocyanine dyes have the potential to target a variety of organelles—both uncharged and positively charged indolizine–merocyanines localize a subset of cellular lysosomes, positively charged indolizine–cyanine hybrid accumulates in mitochondria, while coumarin–merocyanine shows context-dependent localization to mitochondria and RNA-rich nucleoli of the living cells. Graphical Abstract The new merocyanines and cyanines possessing an indolizine scaffold were synthesized via tandem Friedel–Crafts alkylation followed by nucleophilic aromatic substitution, by leveraging the special reactivity of 2,3,5,6-tetrafluoro-4-hydroxybenzaldehyde. Indolizine scaffold as a donor enables the bathochromic shift of emission independent of solvent polarity, whereas indolizine–cyanine selectively marks mitochondria or RNA-rich nucleoli.
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Early view - online Version of Record before inclusion in an issue.
Citation
Angew. Chem. Int. Ed. 2025, e202508044 (1 of 8) // https://doi.org/10.1002/anie.202508044