Chirality is important property of biomolecules, but its detection is often difficult. Therefore we investigated a series of lanthanide tris-(β-diketonates) that are very effective for chirality sensing and amplification in biomolecular substrates. They are electrically neutral and can associate with various small organic molecules, such as chiral alcohols, amino alcohols or amino acids. In organic solvents they often produce a strong chiral signal.
Interaction of the Eu(FOD) complex with (R)- and (S)- enantiomer of 1-phenylethanol in n-hexane was studied using IR spectroscopy, Raman scattering, Raman optical activity (ROA), UV-Vis spectroscopy and ultraviolet circular dichroism (UVCD). Only ROA and UVCD spectroscopies proved to be sensitive enough to the complexation of the studied chemical species.
The UVCD proved especially useful to determine the metal/ligand ratio in the complex. Although lanthanide tris-(β-diketonates) are silent in UVCD spectra, symmetric UVCD signals induced around 300 nm were observed for Eu(FOD) upon complexation with (R)- and (S)- 1-phenylethanol.
In the future, structural variations of lanthanide tris-(β-diketonate) complexes providing enhanced ROA signal are planned; also theoretical modeling may be useful to refine the chirality recognition in biological substrates.