Tetraphenylethenyl Perylene Bisimides

Organic luminophores with aggregation-induced emission (AIE) property emit brightly in solid sate, which is opposite to conventional dyes suffering from heavy aggregation-caused quenching (ACQ) effect. Tetraphenylethene (TPE) is a representative AIE luminophore. AIE opens an avenue to conquring the aggregation-caused quenching (ACQ) effect and deriving luminescent materials with high quantum efficiency in solid state. Researchers have demonstrated that combining TPE moieties with classical fluorogens such as naphthalene, quinoline, anthracene, phenanthracene, carbazole, and pyrene can convert these conventional dyes into efficient solid-state emitters. Perylene bisimides (PBIs) are one class of the most explored organic fluorescent materials due to their high fluorescence quantum efficiency, electron transport property, and ready to form well-tailored supramolecular structures. However, they suffer from heavy aggregation-caused quenching (ACQ) effect which has greatly limited their potential applications. In this thesis, we centered the conversion of PBI from ACQ to AIE.Firstly, we study the fluorescent behaviors of non-, mono-and di-TPE substituted PBI derivatives and the feasibility to convert the fluorescence performance of PBIs from ACQ to AIE. Non-TPE substituted PBI derivatives are typical ACQ luminophore. DBuTPEPBI displays characteristic emission features of perylene bisimides in solution with low quantum yield (2.2%). Its aggregates formed in hexane/DCM (fh=90%) emit red light with moderate quantum yield (9.0%). While, di-TPE substituted PBI derivatives are nonemissive in solutions but highly red-emissive in aggregated state. Unlike those small conjugated systems such as naphthalene, anthracene and so on, whose FL behavior can be completely converted from ACQ to AIE by modification with a single TPE moiety, the modification of the larger PBI core with one TPE moiety can only partially alter its FL property.Secondly, we synthesized novel isomeric PBI derivatives, i.e.1.6-/1,7-DCyDTPEPBI by attaching two TPE moieties to PBI core. They both are AIE active and emit bright red fluorescence in solid state. However, their absorbant spectra and emission indicates1,7-isomer is more conjugated. The fluorescence quantum efficiency of the aggregates of1,7-DCyDTPEPBI (ΦF.solid=29.7%, formed in hexane/dichloromethane mixture,fh=90%) is about424times higher than that in dichloromethane solution (ΦF.soiut=0.07%). Thirdly, we investigated the effects of linking mode on perylene core on the AIE performance. By attaching two tetraphenylethene (TPE) moieties to the1.7-positions by ether linkage, the ACQ-characteristic PBI-derivative was converted to an AIE-characteristic molecule. The of for1.7-DCyDTPEOPBI solid films is as high as13%, corresponding to an AIE amplified factor of433. Although TPE is a conjugated moiety. the optimized molecular geography indicates that the phenyl groups are perpendicular to the perylene core. However, the phenyl rings of the TPE moieties are in a propeller shape, which causes TPE-PBIs AIE active.In addition, morphological inspection demonstrated that TPE-PBIs molecules were easy to form well-organized microstructures despite the linkage of PBI core with bulky TPE moieties. These micro-structures emit bright red fluorescence and demonstrate waveguide activity. Take1.7-DCyDTPEPBI for example, electrochemical investigation results indicated that it sustained the intrinsic n-type semiconductivity of PBI moiety.1,7-DCyDTPEOPBI exhibits several advantages over classical PBI derivatives, including pronounced fluorescence enhancement in aggregate state, red to near infrared emission, and facile fabrication into uniform NPs. Studies on the staining of MCF-7breast cancer cells and in vivo imaging of a tumor-bearing mouse model with DTPEPBI-containing NPs reveal that they are effective fluorescent probes for cancer cell and in vivo tumor diagnosis with high specificity, high photostability and good fluorescence contrast.Finally, we prepared TPENI, TPEDNI and DTPENDI by attaching TPE moieties to the naphthaleneimde and naphthalenediimdes, which are similar with PBIs in properties with small planar structures. TPENI and TPEDNI are ICT and AEE active, with strong emission in solid state (ΦF.s=100%). DTPENDI is nonemissive in solutin, in hexane/DCM mixtures with high hexane fractions (fh≥90%). SEM images demonstrate that DTPENDI molecules are easy to form well-organized microstructures despite the linkage of PBI core with bulky TPE moieties.