Multifunctional 4,5-Diphenyl-1H-imidazole-Based Luminogens as Near UV/Deep Blue Emitters/Hosts for Organic Light-Emitting Diodes and Selective Picric Acid Detection

A series of luminophores (construction of diphenylimidazole (m-CF3PTPI) groups functionalized at the N1-positions of imidazole groups) were purposefully designed and synthesized for optoelectronics and for selective detection of nitroaromatic compounds. The luminophores showed deep blue emission in solution, solid, and thinfilm matrix with acceptable quantum yield and good thermal stability (5% weight loss at 258-296 degrees C). From electrochemical analysis as well as theoretical calculations, the energy gaps of HOMO-LUMO are found to be in good agreement and all of them showed good triplet energy. The luminophores can be explored as hosts for phosphorescent organic lightemitting diodes (PhOLEDs). Furthermore, the m-CF3PTPI derivatives were used as emitters for fluorescent OLEDs and hosts (m-m-CF3PTPI-1 and m-m-CF3PTPI-2) for triplet dopants in PhOLEDs. Near-UV emissions were observed for all the doped devices that exhibited electroluminescence (EL) peaks at -,380-395 nm with a Commission International deL'Eclairage (CIEy) coordinate of -,0.09. Of all the devices, the m-CF3PTPI-5 (3 wt %)-based device demonstrated a maximum external quantum efficiency (EQE(max)) of 2.8%, power efficiency (PEmax) of 0.9 lm/W, current efficiency (CEmax) of 1.3 cd/A, and brightness of 953 cd/m(2). Moreover, the device was further optimized using a different host approach. SimCP2 displayed the best performance by achieving a high EQE(max) of 4.0% that is near the theoretical limit of fluorescent materials. Furthermore, m-CF3PTPI-1 and m-CF3PTPI-2 possessing triplet energies of 2.67 and 2.63 eV, respectively, were used as hosts for efficient green (Ir(ppy)3-2.4 eV) PhOLEDs. The m-CF3PTPI-2-based device achieved an EQE(max) of 4.8%, CEmax of 17.5 cd/A, PEmax of 13.4 lm/W, and maximum brightness (Lmax) of 4695 cd/m(2), much higher than those of the counterpart m-CF3PTPI-1-based OLED. Furthermore, due to structural functionality, the detection of nitroaromatic compounds was carried out for all the luminophores. They showed high sensitivity toward picric acid, and the sensing mechanism was thoroughly analyzed by using NMR and DFT study.

Automated summary

A series of purposefully designed and synthesized luminophores showed deep blue emission and good thermal stability. They can be used in optoelectronics and selective detection of nitroaromatic compounds, as well as hosts for phosphorescent organic light-emitting diodes (PhOLEDs). Additionally, the luminophores can be used as emitters for fluorescent OLEDs and hosts for triplet dopants in PhOLEDs.