Synthesis of Fluorescent Diarylethenes Having a 2,4,5-Triphenylimidazole Chromophore
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Diarylethenes 1a-4a, having a fluorescent 2,4,5-triphenylimidazole chromophore in the aryl group, were synthesized. Upon excitation of the triphenylimidazole chromophore with 366 nm, 1a-4a underwent photocyclization reactions, and the solutions containing 1a-4a changed color from colorless to red-purple or to blue. The colors disappeared by irradiation with visible (lambda > 480 nm) light. The fluorescence intensity of the solutions also reversibly changed with the photochromic reactions. The fluorescence quantum yields of 1a, 2a, 3a, and 4a were determined to be 4.6, 7.7, 9.1, and 8.4%, respectively. The fluorescence quantum yields decreased with the increase in photocyclization quantum yields.Keywords:
Chromophore
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Gated photochromic molecule: switchable photochromic materials with AIEgen were achieved. Oxidation reagents act as gates to switch the photochromic properties.
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A green-light-emitting iridium(III) complex was prepared that has a photoluminescence quantum yield in a thin-film configuration of almost unity. When used in a simple solid-state single-layer light-emitting electrochemical cell, it yielded an external quantum efficiency of nearly 15% and a power efficiency of 38 Lm/W. We argue that these high external efficiencies are only possible if near-quantitative internal electron-to-photon conversion occurs. This shows that the limiting factor for the efficiency of these devices is the photoluminescence quantum yield in a solid film configuration. The observed efficiencies show the prospect of these simple electroluminescent devices for lighting and signage applications.
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Abstract Six fulgides of indole series are prepared. Three of them are photochromic. The others in which R 1 is hydrogen atom do not show photochromism. Only Z‐E isomerizations occur on irradiation at 365 nm. The effects of molecular structural modifications on photochromic properties are also discussed.
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Photochromic researches on spiropyrans, spirooxazines, naphthopyrans, chalcones, diarylethenes, and fulgides published in 2002 have been reviewed. Photochromic compounds are classified into two categories, thermally reversible compounds such as spiropyrans, spirooxazine, naphthopyrans, and chalcones, and thermally irreversible compounds, such as diarylethenes and fulgides. This review describes new derivatives of both types of compounds, their photochromic performance and possible applications. Azobenzene derivatives are not included.
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Diarylethene
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A new unsymmetrical isomeric photochromic diarylethene, 1-[2-methyl-3-naphthalen-2-[2-methyl-5-(10-phenanthrenyl)-3-thienyperfluorocyclopentene, was designed and synthesized. Its photochromic and fluorescent properties were also investigated in detail. The compound exhibited excellent photochromism, changing from colorless to red after irradiation with UV light both in solution and in PMMA film. Furthermore, the fluorescence intensity of the photochromic diarylethene 1a declined remarkably, when irradiation with UV light.
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Abstract Red emission is one of the three primary colors and is indispensable for full color displays. Fluorescent materials that can generate efficient red electroluminescence (EL) are limited and need to be developed. In this work, we report efficient red emitters based on phenanthro[9,10‐d]imidazole‐naphtho[2,3‐c][1,2,5]thiadiazole donor‐acceptor derivatives. The molecules, abbreviated as PINzP and PINzPCN, exhibited high photoluminescence quantum yield (PLQY) up to unity in doped films. They can also reach a relatively high PLQY of ∼30% in neat films. PINzP and PINzPCN were capable of generating efficient red EL in doped devices with a maximum external quantum efficiency (EQE) of 6.96% and 5.92%, respectively.
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We present the first comprehensive study of the comparison between electroluminescence (EL) quantum efficiency and absolute photoluminescence (PL) quantum yield in various host-guest systems. We find that the maximum quantum yield of solid composite films primarily depends on the quantum yield of the guest molecule itself. In contrast, the maximum quantum efficiency of multilayered devices depends on both guests and hosts. Differences between the maximum quantum efficiency and quantum yield are discussed in terms of the carrier recombination process leading to the creation of the dopant exciton. We also find that in some cases doping prevents exciplex formation and leads to an increase in EL efficiency. This is attributed to rapid energy transfer form the host to the guest molecule followed by efficiency radiative decay.
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