Peri‐Functionalized Tetraazaperylenes: Strong Emitters for Molecular Polaritonics

The functionalization of the peri position of the bay chlorinated tetraazaperylene was investigated by varying the donor behavior of the substituents to assess the resulting photophysical and electrochemical properties. To accomplish this, electron donating alkyl‐ and arylsulfido substituents, methoxy and methyl groups were selectively introduced into the peri position via a nucleophilic aromatic substitution of the perchlorinated tetraazaperylene. Both the alkylated and benzylated thioethers displayed high fluorescence quantum yields of up to 80 %. Compounds from the latter group were integrated in resonant optical microcavities to achieve strong light‐matter coupling. The formation of exciton‐polaritons was observed by angle‐dependent reflectivity and photoluminescence that could be tuned by variation of the concentration of the fluorophores and of the thickness of the cavity.