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

Abstract

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%.

Recent advances in dye-sensitized solar cells

“…The most commonly used organic dyes are generally synthesized via sequential transformation of building blocks by cross-coupling reaction catalyzed by transition metals, a strategy that often requires the preparation of toxic organometallic units (for example, boronic acid/esters and aryl stannanes). Gautun et al [8] displayed the potential of direct C-H arylation, a recent C-C bond-forming method extensively employed in the polymer syntheses, in the preparation of five new 3,6-dithienyl diketopyrrole dyes.…”