Synthesis of blue light emitting bis(triphenylethylene) derivatives: A case of aggregation-induced emission enhancement Xiqi Zhang, Zhenguo Chi * , Bingjia Xu, Haiyin Li, Zhiyong Yang, Xiaofang Li, Siwei Liu, Yi Zhang, Jiarui Xu * PCFM Lab and DSAPM Lab, OFCM Institute, State Key Laboratory of Optoelectronic Materials and Technologies, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275, China article info Article history: Received 29 March 2010 Received in revised form 18 August 2010 Accepted 9 September 2010 Available online 18 September 2010 Keywords: Aggregation-induced emission enhancement High glass transition temperature Blue light emission Bis(triphenylethylene) derivatives Device Synthesis abstract A series of new aggregation-induced emission enhancement derivatives from bis(triphenylethylene) with strong blue-light-emitting properties and high thermal stability have been synthesized. Their maximum fluorescence emission wavelengths range between 464e468 nm, with fluorescence quantum yields of 0.58e0.88. Their glass transition temperatures range from 125  C to 178  C. The obtained experimental results demonstrate the different aggregation-induced emission enhancement phenomena caused by the effect of solvent and formation of both H- and J- aggregation states. An emitting device was fabricated using a bis(triphenylene) derivative in the emitting layer which exhibited a luminance effi- ciency of up to 2 cd/A with a maximum brightness of 548 cd/m 2 . Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction In the past decade, organic luminophores have become of great value to the fields of physiology, chemical engineering and display technology due to their applications as biological probes, chemical sensors, and organic light-emitting diodes [1e4]. However, prob- lems related to the production of blue light-emitting materials with strong brightness, long lifetimes and high glass transition temperatures (T g ) have suppressed their application on an even wider scale. Most luminescent materials exhibit relatively weak emissions in the solid state due to the aggregation of molecules leading to the formation of excimers, which results in emission quenching [5,6]. Thus, considerable effort has been exerted in the search for methods to either suppress the quenching of organic luminophores or to produce significant enhancements in their light emission upon aggregation. In line with this, two novel processes have been identified: (1) aggregation-induced emission enhancement (AIEE) and (2) aggregation-induced emission (AIE) [7e13]. AIEE (or AIE) materials have been found to be promising emitters in the fabrication of electroluminescent devices with high efficiency and stimuli-responsiveness for use in multifunctional switches [14,15]. The T g temperature of an organic luminophore is one of the important factors influencing the stability and lifetime of a device. If a device is heated above the T g of the organic luminophore, irreversible failure can occur. In aggregates, strong clustering of aromatic chromophores is often observed with the spectral shift of a maximum absorption band. In aromatic moieties, the blue shift is usually assigned to the parallel head-to-head alignment of aromatic chromophores, also referred to as H-aggregation. In contrast, a red shift is normally observed when chromophores are aggregated in a head-to-tail manner, which is referred to as J-aggregation. The aggregation state of aromatic chromophores can greatly influence the morphologies of the formed aggregates, as well as their absorption and fluores- cence spectra [16e19]. We have already reported a new class of triphenylethylene carbazole derivatives that display strong blue light emissions, high T g temperatures and AIE effects [20]. For comparison, in this work a new class of bis(triphenylethylene) derivatives were synthesized. These derivatives also show strong blue light emissions and high T g temperatures, but unlike their earlier counterparts, they are AIEE- active. It is expected that these novel compounds can be used as potential materials for blue-light emitters in luminescent devices. * Corresponding authors. Tel.: þ86 20 84112712; fax: þ86 20 84112222. E-mail addresses: chizhg@mail.sysu.edu.cn (Z. Chi), xjr@mail.sysu.edu.cn (J. Xu). Contents lists available at ScienceDirect Dyes and Pigments journal homepage: www.elsevier.com/locate/dyepig 0143-7208/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.dyepig.2010.09.003 Dyes and Pigments 89 (2011) 56e62