Synthesis Of Asymmetric Perylene Bisimide For Self-assembly And Bio-applications

Perylene bisimide (PBI) derivatives display superior photochemical and photophysical stability, high fluorescence quantum yields and strong?-? stacking due to the rigid planar structure. PBIs have been widely studied in various fields, such as optoelectronic device, energy stories,and biological labeling. Asymmetric perylene bisimide is a class of perylene derivative modified with different substituent groups at the imide positions, which provides a new perspective for development of PBIs in various fields. Asymmetric perylene bisimides have two advantages: (1) Active groups can be introduced to the imide positions of PBIs without changing the optical properties of PBIs. The rational asymmetric PBIs can be used as biomaker via the interaction between active groups and biological substance. (2) Different substituent groups at each imide position of asymmetric perylene can provide multiple driven forces that affect the molecular arrangement in self-assembly progress.Therefore, the research of asymmetric perylene bisimide has importance significance for constructing fluorescence system and architectures. In this thesis, a series of asymmetric perylene bisimides have been designed,synthesized and studied in the fields of assembly and bio-applications.First, based on the stability of photochemical and photophysical property,an asymmetric zwitterionic perylene bisimide (AZP) have been synthesised and used as a new kind of long-term cell membrane label.Second, we further investigated the self-assembly behavior of asymmetric zwitterionic perylene in polar/apolar solvent. AZP can assemble into hydrophilic microtube in polar solvent and hydrophobic nanofiber in apolar solvent, which results from different molecular arrangement induced by the polarity of solvent. Third, the ACQ chromophore perylene and the AIE chromophore Tetraphenylethene (TPE) were covalent bonded through a spacer. The fluorescence of TPE was quenched because of intramolecular FRET. Asymmetric TPBI (TPE-PBI) can assemble into nanosheets with solid fluorescence and electrical conducitivity. The general idea and main results of this thesis are as follows:1. By mimicking of plasma membrane structure, an asymmetric zwitterionic perylene bisimide (AZP) has been designed and synthesized.The zwitterionic group endowed AZP with biocompatibility and resistance to non-specific protein adsorption. As shown by Uv-vis/FL spectrum, AZP aggregated in water. The TEM and DLS experiments further revealed that AZP self-assembled into nanovesicles with approximately an average diameter of 215 nm. The AZP nanovesicles dis-assembled into monomer when they were added into lipids or acid aqueous, where the fluorescence intensity of AZP is enhanced along with the dis-assembly. Base on fluorescence signal "off-on" induced by"assembly-disassembly" process, AZP has been used as a superior long-term cell membrane marker in vivo and in vitro.2. We have further studied the self-assembly behavior of three amphiphilic zwitterionic perylene bisimides (AZP, SAP, ATP) in polar/apolar solvent systems. ATP and AZP are asymmetric molecules,whereas SAP is symmetric perylene bisimide. Compared to the planar cores of AZP and SAP, twisted tetrachloroperylene core was introduced in ATP as the skeleton instead of planar perylene. The Uv-vis/FL spectra revealed AZP was a suitable building block for tunable self-assembling.We chose the mixture of chloroform/hexane (V/V, 1/9) as the apolar binary solvent and the mixture of chloroform/acetone (v/v, 1/9) as the polar binary solvent. AZP self-assembled into hydrophilic microtube in polar solvent and hydrophobic nanofiber in apolar solvent as confirmed by TEM and SEM. Unfortunately, ATP and SAP formed random aggregates under similar conditions due to structural defect. The planar perylene core of AZP has strong ?-? stacking, while rational amphiphilic balance of asymmetric AZP adjusts the self-assembly property. Tunable surface wettability of the nanostructures resulted from different intramolecular arrangements driven by ?-? stacking and solvent-solute interaction. This facile method provides a new way in controlling the surface properties based on asymmetric amphiphilic zwitterionic perylene bisimide.3. Asymmetric perylene bisimides TPBI was synthesized through bonding the TPE moietiy to the PBI core with a spacer. TPBI possesses a minimal steric hindrance tail (octyl chain) and bulky head (TPE group),which provides a good balance between the molecular stacking and the fluorescence quantum yield of the assembled nanostructure. As shown by Uv-vis/FL spetrum, TPE is faintly emissive because of the FRET between TPE and perylene. TPBI easily forms well-organized nanosheets that emit bright red fluorescence in the solid state with a high fluorescence quantum yield of 31.4%. XRD and Nano-IR further indicate the nanosheets formed via ?-? stacking and hydrogen bonds. Moreover, the electrical conductivity of the TPBI nanosheets are 0.023 S·cm-1 by current sensing atomic force microscopy. TPBI nanosheets possessing electrical conducitivity and solid fluorescence properties will be further invenstigated in the fields of fluorescence sensor and organic electronic devices.