Lanthanide Podands with a Short Tripodal Ligand: The Missing Piece of Puzzle

A new small tripodal ligand L2 has been synthetized and used for lanthanide complexation in acetonitrile. This podand has a short distance between the carbon anchor and the binding sites, but this structural motif still leads to the formation of stable tripodal mononuclear complexes. Indeed, the crystal structure of a C-3-symmetrical mononuclear complex with Eu-III shows a helical wrapping of binding strands around the cation. Similar tripodal complexes are formed with L2 along the Ln(III) series. The selected ones were characterized with different techniques including NMR, mass spectrometry and spectroscopy. As shown with spectrophotometric and NMR titrations, the LnL2 complexes are moderately stable (log beta similar to 7) but remain unchanged in large metal excess. In addition, luminescence lifetimes confirm the complexation of trivalent lanthanide in a single well-protected coordination environment.

Automated summary

A new small tripodal ligand L2 has been synthesized and used for lanthanide complexation, forming stable mononuclear complexes. The crystal structure of a C-3-symmetrical mononuclear complex with Eu-III exhibits a helical wrapping of binding strands around the cation, and similar complexes are formed along the Ln(III) series. Various techniques were used to characterize the complexes, indicating their moderate stability and ability to remain unchanged in large metal excess. Luminescence lifetimes confirm the complexation of trivalent lanthanide in a single well-protected coordination environment.