Britannica Sources used in this answer

How do enantiomers of coordination compounds affect plane-polarized light?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Structural diagram of the vitamin B12 coenzyme molecule, highlighting its organometallic core with five nitrogen-cobalt bonds and one cobalt-carbon bond at the center, surrounded by complex organic groups. — coordination compound Coordination compounds contain a central metal atom surrounded by nonmetal atoms or groups of atoms, called ligands. For example, vitamin B₁₂ is made up of a central metallic cobalt ion bound to multiple nitrogen-containing ligands.

Enantiomers of coordination compounds are optical isomers that possess the ability to rotate the plane of polarization of a beam of light passed through them.21

Because these molecules are non-superimposable mirror images of one another, they rotate plane-polarized light in opposite directions. This phenomenon is characterized by the following:2

Dextrorotatory (+): The substance rotates the plane of light clockwise, as viewed by an observer facing the light source.1
Levorotatory (-): The substance rotates the plane of light counterclockwise.1

This property, known as optical activity, arises from the dissymmetric arrangement of atoms within the coordination complex or the presence of an asymmetric ligand. Additionally, optically active media may exhibit circular dichroism, which is the unequal absorption of right and left circularly polarized light components.213