Tetramethoxy substituted alkyl-acridiniums (TMAcr+) are readily available by facile nucleophilic aromatic substitution on tris(2,6-dimethoxyphenyl)carbenium, but are non-fluorescent, presumably due to intramolecular photoinduced electron transfer quenching. In this work we introduce electron withdrawing groups by electrophilic aromatic substitution reactions, leading to fluorescence turn-on. The acridiniums are moderately fluorescent (φf=20 %) with long fluorescene lifetimes (τf=9 ns). The positive excited state reduction potentials (E*red=+1.6 V) make the TMAcr+ excellent electron acceptors in the excited state, and efficient reductive photoredox catalysts able to oxidize a broad range of substrates.
Keywords: Acridinium; Fluorescence; Organic chromophores; Photocatalysis; Photoinduced electron transfer.
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