Diketone Ligands

Diketone Ligands

The diketone ligand refers to a ketone ligand that has a β-diketone structure (1,3-diketone structure) in its structure. The diketone ligand has a plurality of strongly coordinated oxygen atoms and thus has a strong coordination ability. Diketone ligands can form a variety of coordination compounds. Different coordination compounds have different physicochemical properties, making them widely used in many fields.

Figure 1. β-diketone ligand

Applications

As an excellent chelating ligand, β-diketone has a wide range of applications in the field of heat stabilizers, luminescence, catalysis and extraction.

• Heat stabilizers: Compared with metal heat stabilizers, β-diketone heat stabilizers have excellent initial coloring ability and long-term stability. They are used as auxiliary stabilizers for metal soap stabilizers to solve the weather resistance of original metal soap stabilizers. The serious shortage has greatly expanded the application range of metal soap stabilizers. In recent years, the role of β-diketones has been recognized by more and more people. The β-diketone compound can be used as a heat stabilizer because the β-diketone compound can be complexed with various stabilizers. Through the synergy between the components, the transparency of the polyvinyl chloride product and the "precipitation" and "zinc burning" in the processing process are effectively improved.
• Luminescent material: The β-diketone ligand has the characteristics of large molar absorption coefficient, high fluorescence quantum yield, large Stokes shift, and strong electron transfer ability, and is a good metal chelating agent. Since the diketone ligand has a plurality of strongly coordinated oxygen atoms, it can form a stable complex with the rare earth ions. The complex formed by the rare earth ion and the β-diketone compound can absorb ultraviolet light, and can transfer the absorbed energy to the rare earth ion through the ligand, so that the rare earth ion emits characteristic fluorescence. Due to its stable chemical properties and excellent luminescence properties, it can be used in light energy conversion agricultural film, organic thin film electroluminescence, light-emitting diode, ultraviolet fluorescent material, optical fiber sensor, fluorescent anti-counterfeiting mark, immunofluorescence analysis, trace element analysis, etc.
• Catalyst: The complex of diketone ligand with rare earth ions has a very important application in the fields of polymer synthesis and organic synthesis. This type of catalyst can solve the problem of long chain branching in the synthesis of high molecular weight polyethylene by conventional Z-N catalysts. In particular, acetylacetone-based rare earth complex catalysts are more widely used in organic synthesis. Such catalysts not only have high stereoregularity, but also have a faster catalytic rate. It can also be used as a catalyst for the polymerization of epichlorohydrin, such as epichlorohydrin ring-opening polymerization and copolymerization. In addition, the rare earth β-diketone complex is also a common catalyst for oligomerization.
• Extracting agent: The diketone ligand-forming compound acts as a chelate-type extractant to efficiently extract a variety of common metal ions.
• Other applications: β-diketones have a very important role in other fields due to their special structure. For example, diketone ligands are also used in the preparation of new display devices for gas chromatography separation and displacement agents in nuclear magnetic resonance spectroscopy.

References

1. Gilberto F. (1998). “A novel fluorinated Eu(Ⅲ)β-diketone complex as thin film for optical de?vice applications.” Optical materials 1(1), 23-28.
2. Horrocks W D. (1984). “Lanthanide Ion Luminescence in Coordination Chemistry and Biochemistry.” John Wiley & Sons, Inc 31, 1-104
3. Whan R E. (1962), “Luminescence studies of rare earth complexes: Benzoylacetonate and dibenzoylmethide chelates.” Journal of Molecular Spectroscopy 8, 315-327.