Ultra-long organic RTP host–guest doped systems based on pure 4-(1H-imidazole-1-yl)methyl benzoate as versatile hosts†

Abstract

Pure organic ultra-long room temperature phosphorescence (ULRTP) has attracted considerable attention due to its excellent solubility and abundant resources. Notably, trace impurities in raw organic materials obtained from commercial sources may exert an unpredictable influence on RTP. In this work, we obtained pure 4-(1H-imidazole-1-yl)methyl benzoate (MIBA) powder and its crystals (MIBA)_n after continuous purification. Compared to the raw powder (300 ms) purchased from commercial sources and its crude crystals (MIBA)_n (978 ms), the pure MIBA powder (6.89 ms) and its crystals (MIBA)_n (4.99 ms) display shorter phosphorescence lifetimes, indicating that trace impurities significantly impact their RTP properties. After further isolation and purification, we fortunately obtain an impurity, 4-(1H-imidazole-1-yl)benzoic acid (HIBA), from the trace impurities. Based on the clear structure of HIBA, we design some guest molecules and utilize the host–guest doping method to construct a series of two-component RTP systems. Eventually, an ULRTP lifetime of up to 1.139 s is attained in the two-component RTP system. Furthermore, multi-level anti-counterfeiting is demonstrated by utilizing the time-resolved phosphorescence doped system. This research clearly illustrates that the trace impurities exert a remarkable influence on the phosphorescence properties of the aforesaid compounds and provides a practical strategy for designing new amorphous host–guest molecules for ULRTP systems.