Synthesis, crystal structure and luminescent properties of p-diphenylsulphone compounds with different substituents

Organic light-emitting diodes (OLEDs) with thermally activated delayed fluorescence (TADF) properties have emerged as cheaper alternatives to high-performance phosphorescent OLEDs with noble-metal-based dopants. In this work, five p-diphenylsulphone derivatives bearing different substitutes (R = H (1a), tert-butyl (1b), trifluoromethyl (1c), carbazolyl (1d) and diphenylamine (1e)) were designed and synthesized. Their photophysical properties were investigated via spectroscopic and theoretical methods. These materials emit violet to blue fluorescence ranging from 326 to 488 nm in dichloromethane solution, and show long-lived luminescence with lifetimes ranging from 7.38 to 13.85 μs. The maximal wavelength of UV absorption and photoluminescence are red-shifted in accordance with not only the electron-donating ability of the terminal substituents, but also the extension of the π-conjugation. The photoluminescent properties as well as crystal structure were investigated with the aim of providing the basis for elucidating structure-physical property relationships in the context of potentially efficient OLED materials.