Revealing the intrinsic mechanism of the influence of different rings and oxidized structures on the room temperature phosphorescence

The effect of pure organic room temperature phosphorescence emission and its influence on the electronic structure and photochemical properties of thiophene and diketone derivatives with different ring structures and oxidation state structures were investigated. The results indicate that as the compound oxidizes, its molecular structure undergoes significant distortion to promote intersystem crossing, ultimately achieving room temperature phosphorescence. [Display omitted] •Oxidized compounds exhibit strong photosensitive activity and instability.•The different ring structures and oxidation products have significant effects on the photochemical properties of thiophene and tonone derivatives.•The UV absorption and fluorescence emission of oxidized compounds show a significant red shift.•The molecular structure undergoes significant distortion to promote intersystem crossing as the compound oxidizes. In this work, we used density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods to study the mechanism of pure organic room temperature phosphorescence emission. The effects on the electronic structure and photochemical properties of thiophene and diketone derivatives with different cyclic and oxidized structures. The result suggests that varying ring configurations and oxidation products significantly influence the photochemical characteristics of thiophene and diketone derivatives. The complex experiences conformational distortion along with the oxidation product, which causes notable alterations in the energy gap and charge density of its frontier molecular orbitals. An oxidation process significantly distorts the molecular structure of the compound, leading to excited singlet and excited triplet states structural similarities. With energy gaps dropping from 0.22 eV to 0.05 eV and spin–orbit coupling constants rising from 0.42 cm−1 to 57.48 cm−1, the excited singlet and excited triplet states share structures and charge distributions that increase the energy level channels appropriate for intersystem crossing. Therefore, this work can provide theoretical support for the design and structural optimization of highly efficient pure organic phosphorescent materials.