The Perfluoroadamantyl group: a bulky and highly electron-withdrawing substituent in thermally activated delayed fluorescence materials

The present paper reports development of new thermally activated delayed fluorescence (TADF) molecules with the acridan-triazine structure substituted by perfluoroadamantyl (AdF) groups. The AdF group was prepared by perfluorination using fluorine gas, and introduced into the molecules via nucleophilic aromatic substitution. The bulky AdF group made the emitters highly soluble in organic solvents. Furthermore, their lowest unoccupied molecular orbitals (LUMOs) were stabilized by the electron induction from the AdF groups, leading to small highest occupied molecular orbital (HOMO)-LUMO energy gaps. As a result, both emitters showed red-shifted TADF compared to the non-fluorinated analogue. Perfluoroadamantyl (AdF) groups were introduced into the acridan-triazine structure, a representative thermally activated delayed fluorescence (TADF) material. The bulky AdF group made the emitters highly soluble in organic solvents. Furthermore, the electron induction from the AdF groups made HOMO-LUMO energy gaps smaller, resulting in red-shifted TADF compared to the non-fluorinated analogue.