Management of Triplet Electronic Excitations in Derivatives of Phenoxathiin and Benzophenone

High Resolution Image Download MS PowerPoint Slide A series of donor–acceptor (D–A) compounds consisting of phenoxathiin, phenothiazine, or dimethylacridan electron donating moieties and a benzophenone electron accepting core are designed and synthesized via the Suzuki or Buchwald–Hartwig cross-coupling reaction. By varying the donor units, as well as by introducing heavy bromine atoms into the molecular structure, the impact of nature of the donor moieties on the thermal, electrochemical, and photophysical properties of the benzophenones is studied by theoretical and experimental means. The compounds containing two donor units exhibit higher glass transition temperatures than monosubstituted benzophenones. For molecularly doped polymeric matrices containing 1 wt % of the derivatives with only phenoxathiin units and bromine atoms in their structures, room-temperature phosphorescence is observed. Meanwhile, asymmetric compounds that have phenothiazine or dimethylacridan donor units show thermally activated delayed fluorescence when doped in a polymeric matrix. The polymer molecularly doped with 4-phenoxathiin-4-yl-benzophenone exhibits high sensitivity to oxygen reaching up to 1.8 × 10 –3 ppm –1 . 4-(9,9-Dimethylacridan-10-yl)-4′-(phenoxathiin-4-yl)benzophenone exhibits high hole and electron drift mobilities of 6.9 × 10 –4 cm 2 /(V s) and 7.8 × 10 –4 cm 2 /(V s), respectively at the electric field of 5.14 × 10 5 V/cm. It also shows good performance in the emissive layer of the organic light emitting diode characterized by an external quantum efficiency of 17%. This work signifies the importance of the rational design of derivatives of phenoxathiin and benzophenone as emitters for the effective utilization of triplet energy in optical and optoelectronic applications.