Synthesis and Photophysical Properties of N‐Arylated Diketopyrrolopyrroles

The N‐arylation of diketopyrrolopyrroles with aryl fluorides free of nitro groups was successfully achieved for the first time. Diketopyrrolopyrroles possessing 3,4‐dimethoxyphenyl and benzofuryl substituents underwent reaction with, for example, pentafluoropyridine, in the presence of K2CO3 in N‐methyl‐2‐pyrrolidone to give the desired products in moderate yields. Their photophysical properties in solution were found not to differ significantly from those of analogous N‐alkylated diketopyrrolopyrroles, whereas in contrast to the latter compounds, they were found to possess fluorescence in the solid state. The photophysical properties of all compounds were rationalized by using time‐dependent density functional theory. The N‐arylation of diketopyrrolopyrroles with aryl fluorides lacking a NO2 group is possible. The resulting dyes possess strong orange‐to‐red emission in solution. Their fluorescence in the solid state strongly depends on the nature of the N‐aryl substituent, which forms with the core a dihedral angle of ca. 40–60° in both the ground and excited states.