Bipyridyl-substituted benzo[1,2,3]triazoles as a thermally stable electron transporting material for organic light-emitting devices

We developed new electron-transporting materials (ETMs) for organic light-emitting devices (OLEDs) based on benzo[1,2,3] triazole and two bipyridines. Four derivatives based on the same skeleton were synthesized with four different substituents: phenyl (BpyBTAZ-Ph), biphenyl (-BP), m-terphenyl (-mTP), and o-terphenyl (-oTP). These BpyBTAZ compounds have good thermal stabilities, and their decomposition temperatures were greater than 410 degrees C, which is significantly higher than that of tris(8-quinolinolato) aluminium (Alq), the conventional OLED material. BpyBTAZ compounds show preferable amorphous nature, and moreover, the glass transition temperatures (T(g)s) of both BpyBTAZ-TP compounds exceed 100 degrees C. Furthermore, BpyBTAZ-BP exhibits no melting point and is fully amorphous. The electron affinities of the materials are as large as 3.3 eV and their electron mobility is sufficiently high. These characteristics accounted for a reduction in the operational voltage of OLEDs with BpyBTAZ compounds compared with the reference device with Alq as an ETM. Specifically, the electron mobility of all the BpyBTAZ compounds exceeds 1 x 10(-4) cm(2) V(-1) s(-1) at an electric field of 1 MV cm(-1). In addition, it was revealed that both BpyBTAZ-TP-based devices showed longer luminous lifetimes and smaller voltage increases during continuous operation at 50 mA cm(-2), compared with the Alq reference device.ArticleJOURNAL OF MATERIALS CHEMISTRY. 21(32):11791-11799 (2011)journal articl

<i>N</i>‑Heterocyclic Carbene Catalyzed Oxidative Coupling of Aldehydes with Carbodiimides under Aerobic Conditions: Efficient Synthesis of <i>N</i>‑Acylureas

The oxidative coupling reaction of aldehydes with <i>N,N</i>′-disubstituted carbodiimides catalyzed by <i>N</i>-heterocyclic carbenes under aerobic conditions has been achieved. This reaction gives the corresponding <i>N</i>-acylurea derivatives in good to high yields. Various kinds of aldehydes including aliphatic ones and carbodiimides are applicable to this reaction

<i>N</i>‑Heterocyclic Carbene Catalyzed Oxidative Coupling of Aldehydes with Carbodiimides under Aerobic Conditions: Efficient Synthesis of <i>N</i>‑Acylureas

The oxidative coupling reaction of aldehydes with <i>N,N</i>′-disubstituted carbodiimides catalyzed by <i>N</i>-heterocyclic carbenes under aerobic conditions has been achieved. This reaction gives the corresponding <i>N</i>-acylurea derivatives in good to high yields. Various kinds of aldehydes including aliphatic ones and carbodiimides are applicable to this reaction