Lanthanide induced linkage of bifunctional organic acids

Lanthanides have become a useful tool in NMR spectroscopy within the last 40 years. Due to their paramagnetic properties they can be utilized as probes to determine the binding sites of biologically or environmentally relevant organic molecules as they cause significant line broadenings and / or paramagnetic induced shifts.
In our former and actual research we investigate the interactions, thermodynamic and kinetic behaviour of actinides and biomolecules. Lanthanides can easily be used as inactive analogues for trivalent actinides in consequence of their similar chemistry.
As one major result, determined by solution and solid state NMR spectroscopy, we have found out that lanthanide ions are able to act as linkers to build up polymeric structures of bifunctional organic acids such as pyromellitic acid [1] or phosphorylated amino acids. For instance, in the case of O-phospho-L-serine the lanthanide ions can serve as a bridge between the carboxylate and the phosphate group of two amino acid molecules to form repetitive macromolecules. The influence of pH and temperature has also been studied.
The results were confirmed by dynamic light scattering and FT-IR spectroscopy as well as by isothermal titration calorimetry and laser-induced fluorescence spectroscopy.
Future investigations will focus on actinides, in particular the trivalent americium ion, possibly showing similar chemical reactions.

[1] A. Barkleit, S. Tsushima, O. Savchuk, J. Philipp, K. Heim, M. Acker, S. Taut, K. Fahmy, Inorg. Chem. 50 (2011), 5451-5459.