Expanding the carbo ‐Benzene Chemical Space for Electron‐Accepting Ability: Trifluorotolyl/Tertiobutyl Substitution Balance

With the view to altering the lipophilicity and electron accepting ability of the tetraphenyl-carbo-benzene scaffold, peripheral fluorination of the C-18 ring through aromatic linkers was envisaged from the C18Ph6 and o-(Bu2C18Ph4)-Bu-t references, by replacement of two Ph substituents with two p-CF3-C6H4 counterparts ((F)Tol). The synthesis relied on a [8+10] macrocyclization involving a common bis(trifluorotolyl)-tetraynedione, followed by reductive aromatization of the resulting [6]pericyclynediols. While p-(F)Tol(2)C(18)Ph(4) proved to be hardly tractable due to an extremely low solubility, p-(F)Tol(2)-o-(Bu2C18Ph2)-Bu-t could be extensively studied by X-ray crystallography, NMR and UV/Vis spectroscopy, voltammetry, STM imaging of monolayers, and AFM imaging of binary films with P3HT or PC71BM fabricated by spin-coating for organic photovoltaic cells and J-V curve measurement thereof. The electronic and polarity properties are correlated with moderate but consistent electron-withdrawing effects of the CF3 groups, in agreement with the DFT-calculated frontier orbitals and multipole moments. The results provide guidelines for optimization of fluorinated carbo-benzene targets.