A ligand is an atom that is capable of providing an electron pair when bonded to a central atom. And when this atom is chiral, such a ligand is referred to as a chiral ligand. Therefore, there are many kinds of chiral ligands. Especially in recent years, there are mainly P, N, carbene and other types of ligands, as well as the dominant C2 symmetry ligands. Due to the rich variety of chiral ligands, the properties of different chiral ligands are not identical, so their functions are not completely consistent, and their application fields are also different.
Due to their wide variety, good performance and many functions, chiral ligands have a wide range of applications in organic chemistry, materials chemistry, analytical chemistry, biomedicine, agriculture and the environment.
- Organic chemistry: Most chiral ligands have good compounding properties and can be combined with metals or metalloids (especially palladium, rhodium, ruthenium, copper, etc.) to form metal catalysts. Due to the specific catalytic performance and enantioselectivity exhibited by such catalysts, they can promote various types of reactions such as reduction reactions, addition reactions and coupling reactions, and can improve reaction yields. Therefore, chiral ligands are most widely used in asymmetric catalysis.
- Material chemistry: Some chiral ligands, such as chiral phosphorus ligands and rare earth elements, have unique luminescent properties. They can be made into luminescent paint, can be mixed with plastic to make various display materials, and can also be used to print various anti-counterfeit trademarks and securities. Some chiral carbon ligands have the characteristics of easy dissociation at low temperatures, and have a wide range of applications in the field of nanomaterials. For example, they can be used to prepare various nano materials such as iron, nickel, tungsten and cobalt.
- Analytical chemistry: Some chiral nitrogen ligands, such as chiral amine ligands, have good special choices of coordination, and can separate ions from the system by forming a coordination compound, which plays an important role in environmental protection.
- Biology and medicine: Metal complexes of macrocyclic polyamine ligands and their derivatives can be used as contrast agents and targeted therapeutic agents to enter human tissues and organs, thus playing an important role in CT, ultrasound imaging, and magnetic resonance imaging techniques. In addition, the amine ligand and the Group IV transition metal can form a complex with good cancer treatment effect, which can be used for the development of anti-cancer and anti-tumor drugs. Amine ligands have specific catalytic properties after binding to metal ions, so they can be used to simulate the catalytic performance of biological enzymes.
- Agriculture: Some chiral ligands can form complexes with central atoms, which can be used to neutralize the acidity and alkalinity in the soil, improve soil quality, thereby increasing crop yields and producing off-season vegetables.
The chiral ligands can be mainly classified into chiral carbon ligands, chiral nitrogen ligands, chiral phosphorus ligands, and the like, depending on the types of atoms that provide electron pairs in the ligand structure.
- Chiral Carbon Ligand: A chiral carbon ligand refers to a ligand whose electrons are provided by a C atom and it has chirality in the structure.
Figure 1. Chiral Carbon Ligand
- Chiral Nitrogen Ligand: A chiral nitrogen ligand refers to a ligand whose electrons are provided by an N atom in the structure and which has chirality.
Figure 2. Chiral nitrogen ligand
- Chiral Phosphorus Ligand: A chiral phosphorus ligand refers to a ligand whose electrons are provided by a P atom and has chirality in the structure.
Figure 3. Chiral Phosphorus Ligand
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