Tripodal polyamines as anion receptors: Extraction and structural studies

Tripodal polyamines based on the tris(2-aminoethyl)amine (tren) platform are useful complexing agents for cations or anions depending on the pH of the solution.[1,2] The binding properties of such compounds can be tuned by the addition of aromatic binding groups to the molecule.
A series of different substituted tren (1-4) derivatives were synthesised and characterised.
Here we present some recent solvent extraction and liquid membrane transport results that show a gradation in anion binding behaviour along I-, Cl-, Br-, CrO4
2-, SO4
2- and PO4
3-.
Finally, structural aspects of the anion complexes formed will be discussed, with the X-ray structure of the bromide complex of ligand 3 being presented.
[1] A.G. Blackman, Polyhedron, 2005, 24, 1-39
[2] K. Wichmann, B. Antonioli, T. Söhnel, M. Wenzel, K. Gloe, K. Gloe, J.R. Price, L. F.
Lindoy, A.J. Blake, M. Schröder, Coord. Chem. Rev., 2006, 250, 2987-3003