Studies on Ultralong Lifetime Room Temperature Phosphorescence from Crystals of Phenylpyridinyl Carbazoles

Developing pure organic room-temperature phosphorescence (RTP) substances with extremely long lifetime spans are challenging. This communication reports phenylpyridinyl carbazole-based crystals with ultralong RTP. Nitrogen atoms enhanced intramolecular charge transfer (ICT) and intersystem crossing (ISC), enabling 9-PPC crystals to exhibit a phosphorescent lifetime of 809.3 ms (1.52% phosphorescent quantum yield). The derivatives lacking nitrogen (9-BPC, 4-FPP) showed reduced phosphorescent lifetimes (112.1 ms, 40.3 ms), while methyl-substituted analogs (2-Me-9-PPC, 3-Me-9-PPC, Bi-Me-9-PPC) demonstrated dual effects: suppressing vibrations but disrupting π–π stacking (phosphorescent lifetimes: 277.2 ms, 189.2 ms, and 238.5 ms). Single-crystal structure analysis revealed rigid π–π stacking and C–H···N hydrogen bonds in 9-PPC, stabilizing triplet states. Furthermore, compounds with distinct phosphorescence lifetimes were successfully applied in information encryption and anticounterfeiting inks, highlighting their potential for multifunctional applications. This work highlights molecular-crystal synergy for organic RTP design.