Synthesis, Solubilization, and Photophysical Properties of Polyfluorinated Pentacene Dimers

ABSTRACT A polyfluorinated pentacene dimer, linked with a 1,3‐diethynylphenylene spacer, was synthesized to investigate the effects of fluorination on the dynamics of singlet fission (SF). The incorporation of bulky 4,6‐substituents on the phenylene spacer was necessary to improve the solubility of the fluorinated dimers, toward easier purification and analysis. Photophysical characterization shows that the incorporation of fluorine at the peripheral positions of the pentacene moieties inhibits the solvent dependence of the excited state observed in a nonfluorinated pentacene reference compound. Computational analysis suggests that fluorination drives efficient intramolecular π‐stacking, limiting conformational flexibility. The results confirm that the reduction of polarizability and rotational freedom of the pentacene groups, imposed by fluorination, eliminates the influence of solvent polarity on singlet fission kinetics. The kinetic stability of the fluorinated and nonfluorinated dimers toward photosensitized endoperoxidation with O 2 is also assessed and shows that SF contributes to the stability of nonfluorinated pentacenes, but not necessarily to the stability of their fluorinated counterparts.