Synthesis And Photophysical Properties Of Covalently Linked Perylene Imide Two Poly Body

Photosynthesis is arguably the most important biological process on earth. By liberating oxygen and consuming carbon dioxide, it has transformed the world into the hospitable environment we know today. Directly or indirectly, photosynthesis fills all of our food requirements and many of our needs for fiber and building materials. The energy stored in petroleum, natural gas and coal all came from the sun via photosynthesis. This being the case, scientific research into photosynthesis is vitally important.In this thesis, we have prepared a series of perylene tetarcarboxylic diimides (PDIs) derivatives which were covalently linked by different linkage in a head-to-tail way. The most significant feature of these compounds is that there is no interaction at ground state but with short center to center distance between PDI unites. This will hinder the photoinduced electron transfer and enhance the photoinduced energy transfer between PDI unites and provide us an ideal model to study the light harvesting properties in a PDI array. 1. Molecular design and synthesisWe introduced four p-t-butylphenoxyl groups into the bay positions of perylene ring in order to increasing the solubility of these compounds in organic solvents, this will benefit the purification and characterization of these compounds. The tetraphenoxyl groups substituted perylene dianhydride was prepared by nudeophilic substitution of halogens by phenol groups from tertachloro or tetrabromo perylene dianhydride. Our results suggested that the reaction of tetrachloroperylene dianhydride was quick with high yields, and the most important it is commercially available. Therefore we choose chloroperylene dianhydried as the starting material through out this work. The reactions following are the condensations of dianhydried with amino compounds. Our results indicate that alkyl amines are much more reactive than aromatic amines in this reaction. The reaction of perylene dianhydried with n-butyl amine or ethylenediamine can be carried out in chloroform at room temperature while the reaction with 1,4-diamonobenzene can only happen in reflexing toluene with imidazol as catalyst. Hydrazine showed the best reactivity, the reaction of it with dianhydried finished in several seconds at room temperature in chloroform.The reaction of perylene dianhydried with n-butylamine give two products, the monoimide and diimide. Because of the similar polarity of these two compounds, the separation of these two compounds by column chromatography is very difficult and always results in low product yield. To avoid this repeating and time consuming purification long purification procedures, we did not try to separate it from the reaction mixture and just make it further reacts with amino compounds (hydrazine, ethylenediamine, and or 1,4-diaminobenzene) to give the asymmetrically substituted diimide compounds, which can be separated by column chromatography more easily.Solvent is another aspect which influences the reactions effectively. Organic solvents, such as chloroform, pyridine, toluene, quinoline and DMF are the customarily used solvents for the condensation reactions between dianhydried and amino compounds. But from our experiments, we found that the reaction in reflexing pyridine always results in some side products which difficult to be separated from the product and leads to very low product yield. Toluene with imidazole is found to be the best solvents for this reaction with quit straight forward reaction rate and good product yield.In order to obtain dimer, we firstly prepared perylene monoimide andydried by controlling the mole ratio between perylene dianhydried and n-butylamine. The product was further reacted with hydrazine, diethyleneamine or 1,4-diaminobenzene to give the target dimers.The trimers were prepared in two steps. The first one is the reaction of perylene dianhydried with excess of diamino compounds (hydrazine, ethylenediamine, and or 1,4-diaminobenzene) which gives perylene diimide compounds with free amino groups. This compounds were further reacts with perylene monimide anhydride produce the target compound in reasonable yield.All the compounds give satisfied proton NMR spectra and MALDI-tof mass spectra. 2. Photophysical measurements. The photophyscial properties of these compound were investigated by the UV-vis and fluorescence spectra. The fluorescence quantum yields were calculated with corresponding monomer as standard. The fluorescence lifetime were measured by a phase modulation method. Following results were deduced from the results:1) There is no detectable interaction between perylene unites in dimer and trimer at ground states as revealed by the UV-vis absorption spectra.2) All the compounds give similar fluorescence spectra with same emission bands indicate that there is no interactions between the HOMO and LUMO orbitals of neighboring perylene unites.3) Lifetime measurements on tetrasubstituted perylene diimide give one fluorescence lifetime of 6.35 ns, which is longer than the disubstituted perylene diimide compounds, indicating the steric hindrance introduced by the four bulky groups have make the molecules more rigid and the excited states are stabilized.4) The dimers and trimers show two lifetimes with the longer one at about 6.35 ns corresponding to the emission of perylene diimide monomer and short one between 1.63-0.92ns which can be ascribed to the immigration of the excited state between neighboring perylene rings. This result indicates that these compound is indeed an ideal model for the light-harvesting system in photosynthesis.5) With phthalocyanine as an energy acceptor and perylene diimide as donor, we have also studied the photoinduced energy transfer between phthalocyanine and perylene diimide. The fluorescence spectra revealed the singlet-singlet energy transfer from perylene diimide to phthalocyanine. The straight Stern-Volmer fluorescence quenching curves indicate that the energy transfer is an intermolecular dynamic process with the diffusion process determines the energy transfer rate.3. A fluorescence sensor based on perylene diimdieA fluorescence sensor based on the perylene diimide and diethanol amine was designed and prepared. The perylene unit play as emitter while the diethanol amine play as quencher and detector. Without acid, the fluorescence of perylene diimide was quenched by the diethanol amine because of the photoinduced intramolecular electron transfer from diethanole amine to perylene diimide. But in the presence of acid, the diethanol amine was protonized and the photoinduced electron transfer was harnessed and then the fluorescence of perylene diimide were released. It is well known that diethanol amino groups are capable of coordinated with different metal ions, but in our compound, the diethanol amine did not reacts with Hg²⁺. Pb²⁺, Zn²⁺, and Na⁺ et al probably because the substitution by a phenol group at the nitrogen atom has reduced the coordination ability of diethanolamine with metal ions.