The Synthesis And Optical Study Of Imidazolporphyrin

As porphyrin has a relatively intense emission at the red-light region for its special and stable aromatic macrocyclic structure which is easy to be modified to regulate porperties, it has often been seen as an important alternative red luminescent material to be used in the field of electroluminescence, nonlinear optics, organic photoelectric conversion etc. However, the current practical application of porphyrin as a red-light material is still limited by its low fluorescence quantum yield. To overcome this difficulty, people continuously modify porphyrin structure to screen molecules which have excellent performance, coupling with the deduction of the structure-function of molecular structure and optical properties which is hoped helpful to guide the design practical porphyrin photovoltaic devices.Our research group has continuously been working on this subject for several years and keeping interested in the introduction of aza-aromatic substitute groups in porphyrin. We got some good molecules and accumulated amounts of data. This work continued previous research, it contains the design and synthesis of 23 multi-aryl imidazole derivatives and 11 aza--aromatic substitute porphyrins, the measurement of optical spectrum of these fluorescent compounds, and the calculation on the molecular structure and energy levels of the frontier orbitals to analysis the relationship between molecular structure and optical properties.The main contents of this thesis are as follows:1, A brief introduction represents the prospect of organic light-emitting device, aza-aromatic fluorescent molecules and the research progress of porphyrin chemistry, especially about the development of porphyrin in luminescence field and the design strategy of porphyrin structure.2,23 multi-aryl imidazoles were designed and synthesized. At the same time, their absorption and fluorescence spectrum were measured. The relationship between the imidazoles’ structure and their fluorescent properties was investigated with the help of Gaussian quantization calculation software. The effects of electronic properties of substituents, molecular planarity, and double-imidazole structure on the λmaxab,λmaxem, and the Φf were explored.3, Based on the work of 2, a series of aza-aromatic substituted porphyrins were designed whose structures were optimized by Gaussian quantization calculation software to predict their optical performance. The corresponding synthetic route was also designed:the asymmetric imidazole- porphyrin could be synthesized with mixed aldehyde; the C-N substituted aza-aromatic porphyrin could be synthesized via halogenated porphyrin intermediates and Ullmann coupling reaction; the C-C substituted aza-aromatic porphyrin could be synthesized via formylated porphyrin intermediates and Watt cyclization. Then 11 designed aza-aromatic substituted porphyrins were obtained. At the same time, their absorption and fluorescence spectrum were measured and compared with the quantized calculation results to analyze the relationship between porphyrins’ optic porperties and molecular structure such as the kind of substitute group, the kind of connection bonds, the position of substitute.The results show that the expansion of the aromatic ring increases the absorb region of porphyrin and improves the fluorescence quantum yield; the impact of connected method between imidazole and porphyrin ring is not obviously in the optical spectrum, but the planarity has slight difference. A strong intermolecular energy transfer has been observed which significantly improves the fluorescence quantum yield.4, A green and selective oxidative halogenation of C-H bonds on porphyrins by halides/H2O2 was achieved. Different activities were observed for the three types of aromatic C-H bonds (meso-,β-, and benzo-positions) on porphyrin ring. The oxidative halogenation can selectively substitute porphyrins’meso-H smoothly with Cl-/Br-/1-, but the more active I- could product β-iodide porphyrin at the same time, and the benzo- C-H bond is unreactive in any condition.23 halogenated porphyrins were synthesized in the later experiments, it was confirmed that the reaction can be carried out under various conditions and suitable for aryl-, alkyl- porphyrins or metalloporphyrins. This transformation is facile, efficient, atom-economically and environmentally friendly, could be used to produce β-iodide porphyrin, and is not limited by the poor solubility of porphyrin in organic solvent.