What is the name of the phenomenon that makes the stability of a complex increase when two or more donor atoms

Question

What is the name of the phenomenon that makes the stability of a complex increase when two or more donor atoms are connected by a backbone that allows them to coordinate simultaneously to a metal ion?

Metallic elements tend to act as Lewis acids and form complexes with a variety of Lewis bases. Since most elements are metals, and almost all metals form complexes, it is important to understand these complexes. Many biological molecules, such as the chlorophyll used by plants to harvest the energy of sunlight, are coordination compounds, or compounds containing one or more metal complexes.

Answer 1

Achnatherum hymenoides