Synthesis and spectroscopic properties of conjugated triphenylamino- substituted chromophores Qi Zhong, Lujian Chen, Yu Yang, Yuanjing Cui, Guodong Qian * , Minquan Wang State Key Lab of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, PR China Received 8 September 2006; received in revised form 16 January 2007; accepted 16 January 2007 Available online 27 January 2007 Abstract Two kinds of intramolecular conjugated charge-transfer triphenylamino-substituted chromophores 4-[2-(3-dicyanomethylene-5,5-dime- thylcyclohex-1-enyl)-vinyl]triphenylamine (BHT) and 4,4 0 -bis[2-(3-dicyanomethylene-5,5-dimethyl-cyclohex-1-enyl)vinyl]triphenylamine (BDHT) were synthesized and characterized using 1 H NMR, FTIR and elemental analysis. Their spectroscopic properties were studied in so- lution and in MTES-, VTES-derived bulk materials. It was found that the chromophore with symmetrical structure (BDHT) enhanced fluores- cence quantum yield more than that of the chromophore with asymmetrical structure (BHT). The solvatochromic behaviour of the chromophores in different solvents indicates that the peak wavelength of their solution fluorescence spectrum is related linearly to the solvent polarity ET (30) in the cases of certain solvents. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Synthesis; Triphenylamine; Solvatochromism; Conjugated charge-transfer compounds; Fluorescence 1. Introduction Conjugated organic materials exhibit a variety of interest- ing optical, electrical, photoelectric and magnetic properties in the solid state. The development of organic, electroactive and photoactive materials has progressed markedly in recent times due to their potential applications in molecular and su- pramolecular electronics, light harvesting and photocatalysis. In the meanwhile, they are also found to be important in opto- electronic devices, such as electroluminescence (EL) devices, photoconductors, light emitting devices (LED), solid-state lasers [1e3], biochemical fluorescent technology, non-linear optics, electrogenerated chemiluminescence and photovoltaic cells [4e10]. The advantage of organic over inorganic func- tional materials is the ease of processing and tuning of their properties through simple chemical modification. Among or- ganic functional materials, intramolecular charge-transfer compounds are one of the most important molecular materials, which are functionalized by electron-donating (D) and elec- tron-accepting (A) groups through a p-conjugated link. In the initially excited states, charge transfer and charge separa- tion of these compounds endow them with unique optical and electric properties. The molecules with DepeA struc- tures have attracted much academic and technological re- search interest over the past few years because of their potential applications. By modifying the donors or/and accep- tors, the properties of materials can be readily changed. As we know, there are two kinds of donoreacceptor structures, one is the asymmetrical structure DepeA, such as 4-[2-(3- dicyanomethylene-5,5-dimethylcyclohex-1-enyl)vinyl]triphen- ylamine (BHT) and the other is the symmetrical structure DepeAepeD or AepeDepeA, as exemplified by 4,4 0 -bis[2- (3-dicyanomethylene-5,5-dimethyl-cyclohex-1-enyl)vinyl]trip henylamine (BDHT). As previous studies [11,12] reported that devices based on symmetrical molecules have better per- formance than those based on asymmetrical molecules, it is worthwhile to investigate the structureefunctional property relationship of asymmetrical and symmetrical molecules. * Corresponding author. Tel.: þ86 571 87952334; fax: þ86 571 87951234. E-mail address: gdqian@zju.edu.cn (G. Qian). 0143-7208/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.dyepig.2007.01.006 Dyes and Pigments 76 (2008) 677e683 www.elsevier.com/locate/dyepig