物理化学学报 >> 2004, Vol. 20 >> Issue (08S): 930-935.doi: 10.3866/PKU.WHXB200408zk07

研究论文 上一篇    下一篇

水杨酰苯胺衍生物分子内电荷/质子转移荧光

张煊;郭琳;江云宝   

  1. 厦门大学化学系, 现代分析科学教育部重点实验室, 厦门 361005
  • 收稿日期:2003-12-30 修回日期:2004-04-12 发布日期:2004-08-15
  • 通讯作者: 江云宝 E-mail:ybjiang@xmu.edu.cn

Intramolecular Charge Transfer and Proton Transfer Fluorescence of Salicylanilides

Zhang Xuan;Guo Lin;Jiang Yun-Bao   

  1. Department of Chemistry and the Ministry of Education Key Laboratory of Analytical Sciences, Xiamen University, Xiamen 361005
  • Received:2003-12-30 Revised:2004-04-12 Published:2004-08-15
  • Contact: Jiang Yun-Bao E-mail:ybjiang@xmu.edu.cn

摘要: 将苯甲酰苯胺 (BA) 类电荷转移(CT)反应基团耦合到具有激发态分子内质子转移 (ESIPT) 反应通道的水杨酸 (SA) 分子中,设计合成了苯胺对/间位取代的水杨酰苯胺及其羟基甲基化衍生物邻甲氧基苯甲酰苯胺,考察了环己烷、乙醚、乙腈和甲醇中两类水杨酰苯胺衍生物吸收光谱和荧光光谱的溶剂效应和取代基效应.结果表明,水杨酰苯胺的荧光为SA-型质子转移(PT)荧光,对取代基的依赖性较小;当电子给体苯胺基的给电子能力提高时,如N-甲基水杨酰苯胺分子,其荧光为BA-型CT荧光.而羟基甲基化后的衍生物邻甲氧基苯甲酰苯胺则表现出与BA类似的荧光光谱特性,具有明显的取代基效应.认为水杨酰苯胺衍生物的激发态存在着相互竞争的BA-型CT和SA-型PT通道,二者可经苯胺基上取代基的电子效应调控.

关键词: 苯甲酰苯胺, 水杨酰苯胺, 电荷转移, 质子转移, 取代基效应, 溶剂效应

Abstract: The intramolecular charge transfer (CT) reaction known to occur in benzanilide(BA) derivatives was coupled to salicylic acid (SA) for understanding the substituent effect on the proton transfer fluorescence in comparison with that on the CT fluorescence. A series of salicylanilides 1, in which the SA structural framework was incorporated in the electron acceptor moiety of the BA-like CT fluorophore, were designed and their absorption and fluorescence spectra were investigated in aprotic solvents CHX, DEE, and ACN and a protic solvent MeOH. It was found that 1 exhibited a long-wavelength emission at 470 nm in CHX that scarcely shifted when solvent changed from DEE to ACN of increasing polarity, whereas it drastically shifted to blue at ca 430 nm in protic solvent MeOH. It was therefore made clear that the emission of 1 was different from that of benzanilide, the latter being highly sensitive to solvent polarity. With 2,the o-OH methylated derivatives of 1, long-wavelength fluorescence emission with similar solvent dependence to that of benzanilides was observed. These facts suggested that the emission from 1 originated from the SA-like PT state while that of 2 from the BA-like CT state. The substituent effect on the emission of 1 and 2 with p- or m-substituent at the anilino phenyl ring was examined. Results showed that, whereas the emission of 1 scarcely varied, that of 2 dramatically shifted to the blue with increasing electron-withdrawing ability of the substituent. The emission energies of 2 in CHX were found to be correlated linearly to the Hammett constants of the substituents with a slope of +0.378 eV, close to +0.361 eV observed for benzanilides. It was concluded that the emission of 1 originated from the PT state that showed practically no dependence on solvent polarity and substituent at the proton acceptor moiety.

Key words: Benzanilide, Salicylanilide, Charge transfer, Proton transfer,  Substituent effect, Solvent effect