Effect of Substituents on Aggregation Behaviors of Stilbazole and Stilbazolium Derivatives

Stilbazole and stilbazolium derivatives with dialkylaniline as electron pushing substituents and pyridine or pyridinium substituents as electron drawing substituents were synthesized and their aggregation behaviors were studied by UV-visible, fluorescence and surface photovoltage spectroscopies. Experimental results indicate that the formation of aggregates can be mediated by the electron drawing ability of the substituents introduced for those compounds all bearing strong electron pushing substituent. When the electron drawing substituent is pyridine group, the molecules tend to aggregate in head-to-tail manner, whereas the substituent is pyridinium group, the molecules tend to aggregate in face-to-face manner. The effect of electron pushing and drawing ability of the substituents on the aggregation behavior is further analyzed in terms of frontier orbital interactions.