5,5'-dibromo-3,3'-difluoro-2,2'-bithiophene (2T2F-2Br), CAS number 1619967-08-6, is a double fluorinated brominated bithiophene. The bromo groups at 5,5'-positions enable the intermediate to be further coupled to form C-C bonds via either Suzuki or Stille coupling reactions for the synthesis of more complex conjugated structures, i.e., semiconducting small molecules, oligomers and polymers in application of organic field effect transistors and polymer solar cells. Fluorine atoms on the thiophene rings are electron poor thus down-shift the highest occupied molecular orbital (HOMO) energy level and increasing charge mobility of the targeted polymer donors. Planar structure in the solid state can also be promoted by fluorination in the backbone of the structure via the interaction of the fluoro and sulfur atoms (F⋅⋅⋅S).
Indeed, fluorinated poly(3,4-dialkylterthiophenes) (F-PDATs) exhibited a deeper HOMO energy level than the nonfluorinated PDATs, leading to higher open-circuit voltage in organic solar cells with enhanced molecular ordering in films, showing by a vibronic shoulder peak in UV–Vis spectrum of F-PDATs [1].
2T2F-2Br, 5-Bromo-2-(5-bromo-3-fluorothiophen-2-yl)-3-fluorothiophene