Amine Ligands

An amine ligand refers to a ligand formed by substitution of one or more hydrogens in an ammonia molecule. Amine ligands are electrons provided by N in the structure and are also a class of nitrogen donor ligands. Amine ligands appeared later than other ligands, but they developed rapidly. Due to the wide variety of amine ligands and their strong coordination ability, they have a wide range of applications in organic synthesis, material chemistry and biomedicine.

Applications:

Amine ligands have broad applications in many fields (such as material chemistry, analytical chemistry, organic synthesis, biomedicine) due to their unique and excellent properties.

• Material chemistry: The complexes of amine ligands and rare earth elements possess unique luminescent properties, and they all have strong fluorescence. Such amine complexes can be used for model research of light-converting molecular devices, as well as for the printing of various anti-counterfeit trademarks and securities. In addition, such amine complexes can be made into luminescent coatings and then mixed with plastics to form various display materials. Such an amine complex can even be incorporated into polymers to further form photoluminescent agricultural films, which can significantly improve the quality of farmland.
• Analytical chemistry: Amine ligands can form coordination compounds with a variety of ions due to their good special selective coordination, thereby separating ions from the system. The extensive application of amine ligands in the extraction, enrichment and separation of heavy metal ions is an extremely important method for the treatment of heavy metal ion contamination.
• Organic chemistry: Amine ligands have a wide range of applications in the field of organic synthesis due to their good catalytic activity and high enantioselectivity. Amine ligands can be combined with metals or metalloids to form catalysts, which catalyze a series of reactions such as asymmetric hydrogenation, asymmetric addition, and asymmetric Diels-Alder reaction. In addition, certain amine ligands (e.g., chiral diamine ligands) can be combined with phosphine ligands and perform asymmetric catalysis by molecular self-assembly techniques to facilitate the enantioselectivity of the product.

Classification:

The amine ligands can be classified into monoamine ligands, diamine ligands, and polyamine ligands depending on the number of amino groups contained in the structure.

• Monoamine ligand: A monoamine ligand refers to a ligand that contains only one amine structure, such as NH₃.
• Diamine ligand: A diamine ligand refers to a ligand containing two amine structures, such as 1,2-diphenylethylenediamine.
• Polyamine ligand: A polyamine ligand refers to a ligand containing a plurality of amine structures, such as 1,4,7,10-tetraazacyclododecane (cyclen), 1,4,8,11-tetraazacyclotetradecane (cyliam).

Figure 1. Monoamine ligand

Figure 2. Diamine ligand

Figure 3. Polyamine ligand

References

1. Wu, Jingyun. (2018). "Synthesis, crystal structures, and dye removal properties of aseries of discrete and polymeric copper, zinc, cobalt, and cadmium complexes containing bis-pyridyl-bis-amineligands." Journal of Solid State Chemistry 265, 227-236.
2. Paquet. (2018). "The role of amine ligands in governing film morphology and electrical properties of copper films derived from copper formate-based molecular inks." Nanoscale 10(15), 6911-6921.
3. Hu, Minggang. (2017), "Preparation of zirconium and hafnium complexes containing chiral N atoms from asymmetric tertiary amine ligands, and their catalytic properties for polymerization of rac-lactide." Journal of Molecular Spectroscopy Catalysis Science & Technology 7(6), 1394-1403.
4. Tshabalala. (2015). "Palladium complexes of (benzoimidazol-2-ylmethyl)amine ligands as catalysts for methoxycarbonylation of olefins." Journal of Molecular Catalysis A: Chemical 406, 178-184.