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%.