LAUSR

Abstract Excited triplet state (T1) properties and formation efficiency are key issues in photodynamic therapy (PDT) and organic light emitting diode (OLED). We report hereby the T1 properties, T1 formation efficiency and mechanism for BODIPY parent compound (BDP) using laser flash photolysis technique. We also disclose the singlet oxygen 1O2(1Δg) formation ability of BDP based on NIR phosphorescence and chemical trapping method. More importantly we show that molecular oxygen can strongly increase the T1 and singlet oxygen formation efficiency of BDP up to 5-fold compared to its intrinsic ability due to intersystem crossing. Combining with time-resolved and steady state fluorescence methods, we conclude that the oxygen enhancing mechanism is due to that the energy transfer from the excited singlet state (S1) of BDP to molecular oxygen leads to both T1 and 1O2 formation: BDP(S1) + O2 → BDP(T1) + 1O2(1Δg). This O2 enhancing mechanism for T1 and 1O2 formation is important to understand and design BODIPY photosensitizers in various applications including PDT and OLED.