Twofold C−H Activation Enables Synthesis of a Diazacoronene-Type Fluorophore with Near Infrared Emission Through Isosteric Replacement

The synthesis and photophysical properties of a soluble amide-embedded coronene is reported. The key step in this synthesis is the twofold C−H activation of diazaperylene by a rhodium(III)Cp* catalyst. This unprecedented structural motif shows intense fluorescence in the near infrared region with a small Stokes shift and a distinct vibronic structure, which exhibits a slight extent of negative solvatochromism. Comparison of this compound with some relevant compounds revealed the importance of the amide incorporation in the peripheral concave region including an angular position to retain high aromaticity reflecting that of parent coronene. Treatment of this compound with Lewis acid B(C₆F₅)₃ formed a bis-adduct, which exhibited enhanced aromaticity as a consequence of the increased double bond character of the amide C−N bonds.