Theoretical insight into the effect of the packing modes on the room-temperature phosphorescence phenomenon in 5,5-dioxide phenothiazine derivatives crystals

Abstract

In recent years, oxidized phenothiazine derivatives with low toxicity, environmentally friendly behavior and great photophysical properties have become a research hotspot in room-temperature phosphorescence (RTP) materials. Researchers usually regulate packing modes by introducing different functional groups to obtain different RTP properties. This work focuses on the effect of relative packing mode characterized by overlapping area, vertical distance and slip angle on RTP performance by exploring the electron transition processes of the dimers. The results suggest that 5,5-dioxide phenothiazine derivatives would generate RTP phenomenon when the overlapping area is within 25–60 %, the vertical distance is within 2.1–3.0 Å and the slip angle is within 54–90° after we scanned intermolecular relative positions of the parent skeleton dimers with π–π stacking. In the range of above packing modes, the excitons prefer jumping to high excited singlet states which could generate more triplet excitons through the ISC process, reducing nonradiative transition rate, and transition back to the ground state in the form of RTP radiation, which is verified by some reported experimental oxidized phenothiazine derivatives when we carried out similar calculations on them. This focuses on the overlapping area, vertical distance and slip angle in 5,5-dioxide phenothiazine derivatives could provide interesting findings for the RTP materials.