Porphine Dyes

Porphyrins are a class of macrocyclic heterocyclic compounds formed by the α-carbon atoms of four pyrrole-like subunits interconnected by a methine bridge (= CH-).

Porphine Dyes Figure 1. Structure of Porphyrins.

Introductions

Porphyrins are a class of macrocyclic heterocyclic compounds formed by the α-carbon atoms of four pyrrole-like subunits interconnected by a methine bridge (= CH-). The parent compound is porphin (C20H14N4), and the substituted porphin is called porphyrin. The porphyrin ring has 26 π electrons, is a highly conjugated system, and therefore appears dark. The term "porphyrin" is a transliteration of its English name porphyrin. Its English name is derived from the Greek word meaning purple. Therefore, porphyrin is also known as porphyrin. Many porphyrins exist in nature in the form of coordination with metal ions, such as chlorophyll containing chlorin coordinated with magnesium and heme coordinated with iron. Porphyrins or modified porphyrins can coordinate with metals such as iron, cobalt, and aluminum, and catalyze the copolymerization of carbon dioxide and epoxy compounds under the co-action of co-catalysts. Porphyrin accumulation in the human body can cause porphyria, also known as purpura.

Physical and chemical properties

Porphyrins are generally divided into two categories. The first category is fat-soluble porphyrin compounds, which are usually soluble in organic solvents such as chloroform, dichloromethane, ethyl acetate, and benzene. Small; the second category: water-soluble porphyrin compounds, usually soluble in water, methanol, ethanol, acetone, acetonitrile and other hydrophilic organic solvents. The melting point of porphyrin compounds is usually greater than 300 degrees. The purple-red solid powder or crystalline solid has certain photosensitive properties. It can effectively release singlet oxygen under the action of ultraviolet or visible light.

Applications

Due to the unique optoelectronic properties of porphyrin materials, the use of porphyrin-doped luminescent materials has become a new research hotspot for organic electroluminescent materials. Porphyrin compounds have strong fluorescence in solution, but due to the easy aggregation of porphyrin molecules to generate self-fluorescence quenching, the solid fluorescence is weak and the quantum efficiency is low. Therefore, it is difficult to use a single porphyrin material as a light emitting diode. Porphyrin doping or introduction of porphyrin into polymer chains has become a research hotspot of organic electroluminescent materials, and its main existence form is uncoordinated or metal-coordinated porphyrin.

Synthesis

Early porphyrins were obtained from natural products containing porphyrin compounds by extraction, separation, purification, and other methods, such as heme and chlorophyll. There are two ways to get the target porphyrin molecule: the structural modification of natural porphyrins and the total synthesis of porphyrin compounds. Although the structure modification of natural porphyrins can be easily modified, it is limited by the structure itself. At the same time, the choice of the outer ring functional groups is very limited. In addition, the physiological activities of porphyrin compounds are limited. Therefore, people generally need to obtain porphyrin molecules with specific physiological activities and functions through total synthesis. Through synthetic design, obtaining different types and functions of porphyrin compounds has promoted the development of porphyrin chemistry and broadened its application prospects.