Background and overview[1][2]
Porphyrin is the general name for a class of compounds with different substituents on the porphine ring. It is widely present in organisms and plays an important role in physiological activities, such as heme (iron porphyrin) and chlorophyll (magnesium porphyrin). Porphyrin compounds have a rigid and flexible macrocyclic conjugated structure. They have certain aromaticity, good stability, wide spectral response, and strong metal ion complexing ability.
In recent years, porphyrin chemistry, a research field with great scientific significance and broad application prospects, has attracted more and more research interests from scientists in many fields, such as inorganic chemistry, organic chemistry, analytical chemistry, physical chemistry, materials chemistry, In medicine and biology, etc., interdisciplinary branches related to porphyrin compounds are being formed, and many excellent results have been achieved. In 1967, Alder~1 proposed a classic method to synthesize tetraphenylporphyrin using pyrrole and benzaldehyde.
This method has simple post-processing, washing with methanol and hot water, and has a high yield of the target product. So far, most porphyrin compounds still use this method. In 1991, the synthesis method was improved, using DMF as the solvent, A1CI3 as the catalyst, benzaldehyde, and pyrrole reaction. The yield was about 30%. The disadvantage was that product separation was difficult.
Structure
Apply[2-4]
Porphyrin compounds have a certain degree of aromaticity because their parent porphins have a macrocyclic conjugated structure that is mainly rigid and flexible. It has good stability, wide spectral response and strong metal ion complexing ability. They are generally dark crystals with high melting points. Due to the special structure and properties of porphyrin compounds, they have a wide range of uses.
For example, natural porphyrin compounds have special physiological activities, and many functions in life processes are related to metalloporphyrins. Therefore, it has become important to artificially synthesize porphyrins of various structures to simulate the various properties of natural porphyrin compounds. Research topic. In addition, it has very broad application prospects in many other fields, such as materials chemistry, medicinal chemistry, electrochemistry, photophysics and photochemistry, analytical chemistry, organic chemistry and other fields.
1. Application in medicine
Metalloporphyrin compounds have made breakthrough progress in medicine. Based on the excellent fluorescence properties of metalloporphyrin compounds and the special affinity of many porphyrin compounds to cancer cells, people can use them to identify diseased tissues. For example, the radiation sensitization effect of Cd-porphyrin compounds can be used to effectively diagnose cancer and other difficult diseases.
And this diagnosis is almost non-toxic. Porphyrin compounds such as hematoporphyrin have the ability to combine with cancer cells and be stimulated by light to release singlet oxygen, thereby killing cancer cells and opening up a new way for humans to conquer cancer – photochemotherapy. In addition, metallic calcium porphyrins are all diamagnetic compounds. It also has good stability and is a suitable substitute for iron porphyrin compounds. It can be used as a good model system for studying catalase and drug metabolism in liver cells.
2. Application in biology
Photosynthesis in nature is a highly efficient sensitized redox reaction, with chlorophyll as the electron donor and pheophytin and quinones as electron acceptors. At the same time, metalloporphyrin compounds have the characteristics of being sensitive to light, having a wide spectral response area, long excited state lifetime, and high redox potential. Therefore, people have paid great attention to them in the simulation research of photosynthesis. The concept of supramolecular compounds was proposed by French chemist J. M. Proposed by I ehn, this concept includes complexes formed by the complexation of carriers and small molecules.
Carriers have complexing and activating effects on small molecules. Many processes in organisms, such as hemoglobin carrying oxygen and chlorophyll fixing CO, have given people a lot of inspiration. They can imitate the binding form of living substances to small molecules and synthesize supramolecular compounds to achieve The immobilization and activation of small molecules has become an important development area of biomimetic organic chemistry, because many enzymes in organisms are metalloporphyrin compounds or their analogs. Therefore, porphyrin compounds have received great attention in biomimetic chemistry research.
3. Role in catalysis
A large number of research results show that metalloporphyrin compounds are effective in olefin epoxidation, alkane alcoholization, and aldehyde oxidation reactions.��Good catalytic effect. Recently, it was discovered that the tetraphenylporphyrin-iodophenylene system of chromium can activate C—H bonds under mild conditions. It is a good simulation system for studying cytochrome P-450. It can not only explain the simulation of cytochrome P-450 The system catalyzes the reaction mechanism of oxidation of hydrocarbons, and helps to gain an in-depth understanding of the reaction mechanism of cytochrome P-450 catalytic oxidation of hydrocarbons.
4. Application in materials
Porphyrin compounds have a molecular lattice and low intermolecular interaction energy. After absorbing light, the molecules are excited. The excited porphyrin compounds easily form charged porphyrin free radicals, thus showing the properties of semiconductors. It has a wide range of uses in optoelectronic materials. Porphyrins form disc-mounted metal-organic liquid crystals with many metals. Nowadays, it is found that metal porphyrins such as Cu, Cd, Zn, Co, and Pd all have liquid crystal properties.
If some research has prepared a zinc tetraphenylporphyrin/zinc oxide composite film nanomaterial, the steps are: 1) Synthesize a bird’s nest-shaped ZnO nanofilm material on ITO conductive glass; 2) Synthesize tetraphenylporphyrin phosphine (H2TPP); 3) Dissolve tetraphenylporphyrin in chloroform solvent; 4) Dip the ZnO nanofilm material attached to the ITO conductive glass into the H2TPP solution to immediately achieve uniform spin coating attachment; 5) Place it in a tube furnace and calcine in nitrogen.
During the preparation process, zinc tetraphenylporphyrin (ZnTPP) is self-assembled in situ on the surface of ZnO. The obtained organic and inorganic composite materials have clean interfaces, chemical bonding, and good stability, which not only broadens the scope of composite materials The visible light absorption spectrum can also improve the separation efficiency of photogenerated charges, greatly improve the photocatalytic degradation efficiency, and show hydrophobicity and obvious selectivity for organic dyes. There is also research on methods for preparing lithium iron phosphate/magnesium tetraphenylporphyrin composite cathode materials for lithium-ion batteries, which involves the technical field of lithium-ion batteries.
The method mainly includes the following steps: 1. Preparation of doping precursor: using tetraphenylporphyrin magnesium as the carbon source and magnesium source, using a solvothermal method to prepare lithium iron phosphate/tetraphenylporphyrin magnesium Precursor; 2. Calcination of lithium iron phosphate/magnesium tetraphenylporphyrin precursor: The synthesized precursor is calcined at high temperature to prepare the lithium ion battery cathode material—magnesium tetraphenylporphyrin modified iron phosphate Lithium; 3. Use the synthesized composite material as a cathode material for lithium-ion batteries. Batteries made by the above method have good electrochemical properties.
5. Application in analytical chemistry
Free porphyrin has strong absorption in the visible light region. It can form a 1:1 stable complex with most metal ions and is an excellent reagent for the determination of trace metal ions by spectrophotometry. As early as 1957, tetraphenylporphyrin was used to measure zinc. In recent years, many water-soluble porphyrins and non-water-soluble porphyrins have been prepared and have been used for trace amounts of copper, cadmium, iron, lead, zinc, manganese, and mercury. , magnesium, palladium, cobalt, iron, silver and other metal ions are determined.
Preparation [5]
Add 60mL propionic acid, 20mL nitrobenzene, and 3.85mL benzaldehyde into a three-necked flask equipped with a reflux device and a constant pressure dropping funnel. Stir and heat. When the solution begins to reflux, the temperature is about 140°C. Stir and pass through the constant pressure Add 2.1 mL of freshly steamed pyrrole and 15 mL of nitrobenzene mixture from the dropping funnel (complete the dripping within about 10 minutes). The solution gradually turns purple-black and continues to react under reflux for 4 hours.
After stopping the reaction and cooling to room temperature, add 120 mL of absolute ethanol and let it stand in the refrigerator overnight. Use a Buchner funnel to suction-filter the dark purple solid and wash it repeatedly with absolute ethanol and water until the filtrate is colorless. The product is Put it into a vacuum oven and dry it to get purple crystals. Dissolve the crude product in chloroform, use neutral alumina to wet-pass the column, use chloroform as the eluent, and collect the first purple band. The collected liquid was evaporated with a rotary evaporator to remove the solvent and then placed in a vacuum drying oven to dry for 8 hours to obtain purple crystals. The yield calculated by weighing was 38%.
Main reference materials
[1] Zhao Shengfang, Yang Shuibin, Zheng Yan. Synthesis methods and applications of substituted tetraphenylporphyrin compounds [J]. Journal of Huanggang Normal University, 2004, 24(3): 58-62.
[2] Liu Weiwei, Shao Mingran, Zhao Yueqiang, et al. Synthesis and structural characterization of tetraphenylporphyrin [J]. Journal of Huaihai Institute of Technology, 2004, 13(3): 43-45.
[3] CN201610030408, 2 Preparation method of zinc tetraphenylporphyrin nanomaterial with strong spectral absorption ability and high carrier mobility
[4] CN201610994174, In-situ self-assembly preparation method of zinc tetraphenylporphyrin/zinc oxide composite film nanomaterials
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