Synthesis And Optical Properties Of Thermoresponsive Dendronized-perylene Bisimides

Perylene bisimides (PBIs) are among the most valuable functional dyes, and havepromising applications from supramolecular assembly to optical and electronicmaterials. Recently, much attention has been paid to develop water-soluble PBIs andtheir applications in aqueous media. To afford water-soluble PBIs withstimuli-responsive property can further broaden their applications in biosensors andsmart nano-materials. Herein, we report a novel kind of PBIs modified witholigoethylene glycol (OEG)-based dendrons, which show unprecedentedthermoresponsive properties in aqueous solutions.Four kinds of PBIs with different dendron generations and interior structures orlinkages between dendron and PBI core are reported here. They were efficientlysynthesized through the reaction between perylene tetracarboxylic acid bisanhydridewith the aminated OEG-based dendrons. Their structures were characterizaed by1HNMR spectroscopy and mass spectrometer. Their thermoresponsive behavior andfluorescence properties in aqueous solutions were investigated by temperaturedependent UV/Vis and fluorescence spectroscopies. It was found that all theOEG-dendron modified PBIs show relatively fast phase transitions and smallhysteresis, and their cloud points are dependent on the OEG structures. Interestingly,the PBIs decorated with different OEG dendrons show different fluorescenceemission in aqueous solution at room temperature. Upon heating to above the phasetransition temperature of OEG dendrons, the PBI units start to aggregate and initiategreat fluorescence enhancement, which makes these dendronized PBIs uniquecandidates as thermal fluorescence sensors.