Design, Synthesis And Properties In Heterogeneous Media Of Perylene Tetracarboxylic Diimide Derivatives

Perylenetetracarboxylic diimide (PDI) derivatives are important molecular building blocks that are currently being investigated for use in a variety of photoactive organic materials because of their low light and thermal fading rates, high luminescence efficiency, wide absorption and emission bands in visible region, and optoelectronic properties. They have been used in solar energy conversion, electroluminescence, liquid crystal materials and biological fluorescent probes and so on. In recent years, these dyes have generated more and more attention because of their outstanding luminescence and photophysical properties, and gradually become a research hotspot.Driven by the demands of diverse applications, the modification on molecular structure of PDI aimed at changing the photophysical properties has attracted a lot of research interest in the past decade. How to find a structure with novel properties has been a disturbing problem. In this paper, to find the relationship between structure and properties of PDIs, we designed and synthesis some PDI compounds, and studied their novel properties in depth. The main work of this thesis includes:In chapter 1, the research of synthesis, properties and applications of these perylene diimide derivatives have been reviewed. The topic of special photophysical properties of PDI compounds in special media is selected as the focus of this research.In chapter 2, electron donors were introduced to the imide nitrogen positions by the condensation of perylene dianhydride with amine, and thus compounds 1 and 2 were synthesized in which electron donors were linked by linkages of different length. For the purpose of comparison, compound 3 with electron donors connected at the bay positions was also prepared. Their photophysical properties in room temperature ionic liquid (RTILs) and organic solvents were studied by steady state absorption and emission spectra and fluorescence lifetime measurements. The intramolecular photoinduced electron transfer in 1 and 2 has been efficiently hindered because of the solvation of RTILs, both compound 1 and 2 were proposed to have two conformations (S and F) and the photoinduced electron transfer (PET) can only occurred in conformation F, the conformation change from S to F in RTILs has been blocked because of the large viscosity of the RTILs, therefore, the PET in RTILs was hindered. However, the solvation of RTILs to 3 resembled that of a normal polar organic solvent. Our results presented here revealed that the solvation behavior of RTIL is varied dramatically along with the structure and properties of the solute molecules, and revealed "non-polar" solvation behavior for RTILs for the first time.In chapter 3, a perylenetetracarboxylic diimide (PDI) compound with an attached hydrophilic polyoxyethylene group at the imide nitrogen position was designed and synthesized by the condensation of 1,6,7,12-tetra-substituted perylene dianhydride with amine, it can dissolve freely in a ternary IL microemulsion(bmimPF6/TX-100/H2O). Photoinduced electron and energy transfer between coumarin 153 (C-153) and PDI in non-polar toluene, polar THF and microemulsion were comparatively investigated by steady state electronic absorption and fluorescence spectroscopy. The results revealed that both PDI and C-153 resided at the interface between the surfactant TX-100 and the ionic liquid bmimPF6 in the ternary micoremulsions. The unique micro-environment of IL microemulsion promotes efficient fluorescence quenching of C-153 by accelerating the electron transfer. All these results suggest that it is possible to achieve a full control over the electron or energy transfer by putting the donor or acceptor molecules in different regions of microemulsions. This is meaningful for the design and fabrication of artificial light harvesting systems or photosynthesis reaction centers.In chapter 4, three amphiphilic PDI derivatives (compounds 1,2 and 3) connected with hydrophilic and/or hydrophobic side chains at imide nitrogen positions were synthesized. The gelating abilities of them in different solvents have been investigated, and the results indicated that compounds 1 and 3 can form fluorescent gels whereas compound 2 cannot. The properties of the gels of compounds 1 and 3 have been investigated by UV-vis absorption and emission spectra. The results indicate that the gel of compound 1 is composed of H-aggregates, whereas the gel of compound 3 is composed of J-aggregates. The reversible transformation between gel and solution states induced by temperature change is observed. The structure of dried gel has been investigated by X-ray diffraction (XRD) experiments, and the morphology has been measured by atomic force microscopy (AFM). The results indicate that the face-to-face packing of the PDI molecules driven dominating by the strongπ-πinteraction and formed nanoribbons or network in the gel. This research revealed successfully the crucial roles of molecular planarity, the side-chain conformations and amphiphilic properties in controlling the gelating properties of PDI molecules. This information may be useful for the design of novel organogels based on perylenetetracarboxylic diimides.