Polymeric Amines as Ligands. Polyethyleneimines as Ligands in First and Second Coordination Sphere

Abstract

Polymeric amines, containing the monomeric unit –CH₂–CH₂–NH– (PEI or LPEI). are versatile ligands, forming complexes in aqueous solutions with many labile metal ions, even at relatively low pH, due to the strong chelate effect. The mean distances between the metal centers within a polymer chain is small in solutions with a low ratio N:M, even if the total metal concentration is low. This gives rise to metal–metal interactions, as, e.g., observed by ESR-spectroscopy. Non-labile metal ions, like Pt(II) or Ru(II), form complexes with these ligands too. It is also possible to bind both labile and non-labile metals in the same polymer chain. The polymeric ligand is, in its protonated form, a chelating hydrogen bridge donor, complexing anions as, e.g., cyano complexes strongly. The effects of first and second sphere complexation are discussed and some possible applications are mentioned.

Key Words:

• polymers as ligands
• second sphere complexes
• anion complexation
• magnetic interaction in polymers
• ESR of polymer complexes