Orthogonal conformation regulation enables highly efficient phosphorescence emission in BODIPY-fluorene derivatives without heavy atoms

The BODIPY-Fluorene derivatives with an orthogonal conformation were prepared for the emission of efficient phosphorescence. The derivatives show visible light absorption (497–513 nm), high phosphorescence quantum efficiency (36.2%) and realize control of luminescence color from green to orange-red. Typical orthogonal conformation and smaller excited state (S1 and T4) energy gap (0.05 eV) are favorable for intersystem crossing (ISC) process. The calculation are carried out for rationalization between the photophysical properties and conformation of the BODIPY-Fluorene derivatives. We demonstrate that the conformational substitution positions and the distance between D-A are promising strategy to regulate the emission lifetime and quantum efficiency for BODIPY derivatives. Moreover, the ability to generate singlet oxygen was measured by photooxidation of 1,3-diphenylisobenzofuran (DPBF) by singlet oxygen (1O2) photosensitization. At the same time, the LED device displays bright orange-red emission. This work paves the way for further research into the design and application of such materials in advanced optics.