Synthesis and Properties of Nitrogen-Containing Pyrenes

We
developed a short-step synthesis of 2,4,10-triazapyrenes involving
two sequential C–H substitutions: Pd-catalyzed cross-coupling
reactions via C–H arylation followed by intramolecular Cu-catalyzed
C–H functionalization. This method was successfully applied
to the preparation of 4,10-diaza-, 1,4,10-triaza-, and 1,3,4,10-tetraazapyrenes.
Crystal structure analysis of 5,9-di­(4-methylphenyl)-2,4,10-triazapyrene
showed that planar triazapyrene cores have π-stack packing.
Incorporating nitrogen atoms into the pyrene framework bathochromically
shifted the lowest energy onsets of the absorption bands and increased
the first reduction potentials. The nitrogen-containing pyrenes showed
fluorescence with a weaker intensity (Φf = 0.041–0.12)
than that of the parent pyrene. The number and position of nitrogen
atoms influenced the extent of these effects.