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

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.