Synthesis and aggregation properties of a series of dumbbell polyhedral oligosilsesquioxane-perylene diimide triads

Abstract

A series of perylenetetracarboxylic diimide (PDI) derivatives connected with two bulky polyhedral oligosilsesquioxanes (POSSs) were designed and synthesized for the purpose of revealing the effect of bulky and well-defined side groups on the self-aggregation behaviour of PDIs. The properties of these compounds in solution were investigated by UV-vis absorption spectroscopy, fluorescence spectroscopy, and fluorescence quantum yield measurement. The results indicate that the POSS groups do not show large effects on the spectroscopic properties of PDIs in solution. However, the solid state spectroscopic properties of these compounds are significantly affected by the bulky POSS groups. The presence of bulky POSS groups changes the packing structure of the molecules in the solid state and thus affects the solid state emission properties. Our results revealed that the introduction of bulky POSS groups into the molecules will not inevitably lead to promoted solid state fluorescence quantum yield as expected. It is the packing structure of the molecules in the solid state which determines the solid state fluorescence quantum yield. If the presence of bulky POSS groups leads to the formation of “J” aggregates in the solid state, then the solid state fluorescence quantum yields will be improved significantly. Otherwise, if the bulky POSS groups cause “H” type aggregation of the molecules, the solid state fluorescence quantum yields will be small.