Imine Ligands

Imine Ligands

An imine ligand refers to a ligand having a C=N structure in its structure. Many of the unique electronic properties of imine ligands have great research and application value in the fields of chemical bond formation, olefin polymerization catalysts and biological enzyme mechanism. In particular, the nitrogen atom in the imine ligand, in which the lone pair of electrons can coordinate with a variety of metals with empty orbitals, thereby forming a complex structure, opens up a new era in the field of olefin polymerization, and has been synthesized a lot. Imine ligands can be classified into monodentate imine ligands, bidentate imine ligands, and polydentate imine ligands.

Applications

Because of the unique electronic structure and steric hindrance effect of imine ligands, the complexes produced by them have better stability and have broad application prospects in the fields of life science, materials science and catalytic chemistry. .

• Fluorescent material: The structure of the organic ligand in the metal organic complex has a great influence on the luminous efficiency and the emission wavelength. Since the polydentate imine ligand contains a plurality of C=N structures in the structure, different configurations of isomers can be produced when the spatial arrangement order is different, and these imine ligands are superior in terms of photophysical and electrochemical properties. Complexes formed with heavy metals such as platinum, rhodium, etc. can be applied to the preparation of electrophosphorescent devices.
• Olefin polymerization catalyst: Olefin is a very important chemical raw material, which is a linear olefin with a double bond at one end of the molecule. It is widely used in the production of products such as chemicals, new polyolefin materials, advanced lubricating oils, surfactants, plasticizers, detergents, oil fields according to the chain length. The imine ligand and the transition metal such as homogeneous iron, cobalt, nickel and the like form a catalyst, which can catalyze the oligomerization of ethylene to obtain an ɑ-olefin. The dendritic metal amide catalyst can be used for olefin preparation by adjusting its structure, size, shape, functional group type and solubility to improve its catalytic activity, product selectivity and thermal stability.
• Organic synthesis: The imine metal complex formed by the combination of an imine ligand and a metal is a series of compounds having considerable stability and a certain catalytic effect. These imine metal complexes have good molecular tailoring properties, and can realize specific molecular structure design at the molecular level by adjusting the molecular structure of the imine and the electron and cubic environment of the coordination center, thereby obtaining a catalyst with better catalytic performance. These catalysts can be used to catalyze a variety of reactions in organic synthesis, such as asymmetric synthesis, coupling reactions, etc., and are widely used in the synthesis of natural products, pharmaceuticals, and functional polymer materials. The imine ligands in particular exhibit a good activity for promoting the Suzuki coupling reaction. The palladium complex prepared directly from the hydroxyimine ligand with palladium chloride is a good catalyst for the Suzuki coupling reaction.
• Other applications: The imine ligand can be combined with many transition metals to synthesize metal organic complexes with special thermal and magnetic functions and high selectivity and high activity. These organometallic complexes can be used in industrial material preparation.

Classification

The imine ligand can be classified into monodentate imine ligand, bidentate imine ligand, and polydentate imine ligand depending on the number of coordination atoms contained in the structure.

• Monodentate imine ligand: An imine ligand having only one coordinating atom in the structure is referred to as a monodentate imine ligand.

  Figure 1. Monodentate imine ligand

• Bidentate imine ligand: An imine ligand containing two coordinating atoms in the structure is referred to as a bidentate imine ligand.

  Figure 2. Bidentate imine ligand

• Polydentate imine ligand: An imine ligand having three or more coordinating atoms in the structure is referred to as a polydentate imine ligand.

  Figure 3. Polydentate imine ligand

References

1. Chen, Guan-Hao.(2018). “Synthesis, characterization and cancer cell growth inhibition activity of ruthenium(II) complexes bearing bidentate pyrrole-imine ligands.” Journal of Organometallic Chemistry 868, 122-130.
2. Li, Chen. (2018).“Syntheses, structures and catalytic activities of molybdenum carbonyl complexes based on pyridine-imine ligands.”Transition Metal Chemistry 43(62), 193-199.
3. Rosa, Vitor. (2018). ”Imine ligands based on ferrocene: synthesis, structural and Mossbauer characterization and evaluation as chromogenic and electrochemical sensors for Hg2+.” New Journal of Chemistry 42(5), 3334-3343.