Porphyrin Dimer - Series Of Compounds Perylene Imide Light-induced Energy Transfer And Photoinduced Electron Transfer Research

The most important process in natural photosynthetic reaction center is the quick and efficient multiple-step electron and the energy transfer. This has attracted many researchers to look for ways to duplicate the reactions in simplified chemical systems. To mimic both the charge separate and light harvesting process in photosynthetic protein, the artificial photosynthetic system are normally comprised of electron donors and acceptors which linked by covalent bonds or supramolecular interactions.The versatile optical, redox, and photochemical properties of porphyrins makes them ideal substitute for chlorophylls in artificial photosynthetic systems. It is proved to be a good electron donor in the most of D-A arrays as revealed by numerous literature reports. The perylene tetracarboxylic diimide (PDI) has strong absorption between the porphyrin Soret (B) and Q bands, strong emission with high fluorescence quantum yield, and rational fluorescence lifetime. The particular important is its high stabilities toward heat and light. PDIs can be modified easily on the molecular structure, which not only change photophysical and redox properties, as well as improve the solubility of theses compounds in common organic solvents. Very recently, the D-A systems composed of both porphyrin and PDI became the focus of many research groups. However, the D-A systems. containing face-to-face arranged porphyrin dimer and PDI has never been reported so far. In this thesis, we have prepared several D-A systems composed of a porphyrin dimer and a PDI lined by different bridges. Some novel photophysical properties have been found for these compounds. To the best of our knowledge, this represents the first example of the artificial photosynthetic model, which contains porphyrin dimer and PDI at the same time.The photophysical properties of these two compounds were investigated by the steady state electronic absorption and fluorescecne spectra and the lifetime measurements. The ground state absorption spectra revealed intense interactions between the porphyrin units within the porphyrin dimer but no interactions between porphyirn dimer and PDL The fluorescence spectra suggested an efficient energy transfer from PDI to porphyrin accompanied with a less efficient electron transfer from porphyrin to PDI. The energy transfer is not affected by the dimeric structure of porphyrin as well as the linkage between the porphyrin dimer and PDI. But the electron transfer from porphyrin to PDI is significantly affected by either the linkage between the donor and the acceptor or the polarity of the solvents. The dimeric structure of porphyrin unites in these compounds have promoted the electron transfer in non-polar solvent significantly, but not in polar solvents.