Moving Beyond Cyanoarene Thermally Activated Delayed Fluorescence Compounds as Photocatalysts: An Assessment of the Performance of a Pyrimidyl Sulfone Photocatalyst in Comparison to 4CzIPN.

Carbazolyl dicyanobenzene (CDCB) derivates exhibiting thermally activated delayed fluorescence (TADF) have shown themselves to be excellent photocatalysts over recent years, particularly , although investigation into organic TADF compounds as photocatalysts outside of the CDCB group has been limited. Herein, we report an alternative donor-acceptor TADF structure, 9,9'-(sulfonylbis(pyrimidine-5,2-diyl))bis(3,6-di--butyl-9H-carbazole), , for use as a photocatalyst (PC). A comparison of the electrochemical and photophysical properties of with in a range of solvents identifies the former as a better ground state reducing agent and photoreductant, while both exhibit similar oxidation capabilities in the ground and excited state. The increased conjugation of relative to presents a more intense CT band in the UV-vis absorption spectrum, aiding in the light absorption of this molecule. Prompt and delayed emission lifetimes are observed for , confirming the TADF nature, both of which are sufficiently long-lived to participate in productive photochemistry. These combined properties make useful in photocatalysis reactions, covering a range of photoredox oxidative and reductive quenching reactions, as well as those involving a dual Ni(II) cocatalyst, alongside energy transfer processes. The higher triplet energy and increased photostability of compared with were found to be advantages of this organic PC.