Synthesis of Novel 3,6-Dithienyl Diketopyrrolopyrrole Dyes by Direct C‒H Arylation.

Direct C‒H arylation coupling is potentially a more economical and sustainable process than conventional cross-coupling. However, this method has found limited application in the synthesis of organic dyes for dye‒sensitized solar cells. Although direct C‒H arylation is not an universal solution to any cross-coupling reactions, it efficiently complements conventional sp2‒sp2 bond formation and can provide shorter and more efficient routes to diketopyrrolopyrrole dyes. Here, we have applied palladium catalyzed direct C‒H arylation in the synthesis of five new 3,6-dithienyl diketopyrrolopyrrole dyes. All prepared sensitizers display broad absorption from 350 nm up to 800 nm with high molar extinction coefficients. The dye‒sensitized solar cells based on these dyes exhibit a power conversion efficiency in the range of 2.9 to 3.4%.