Complexation Behavior of Pinene-Bipyridine Ligands towards Lanthanides: The Influence of the Carboxylic Arm

The complexation behavior of two novel, chiral pinene-bipyridine-type ligands ((-)-HL1 and (-)-HL2) containing a carboxylic arm towards lanthanide Ln(III) (Ln = La, Eu, Lu) ions was investigated through spectroscopic methods. The association constants of the mononuclear complexes determined from the UV-Vis titrations indicated that the ligand (-)-HL1 possessing a shorter carboxylic arm formed more stable complexes compared with (-)-HL2, whose carboxylic arm had one more methylene unit. This is due to the formation of more stable seven-member metal chelate rings in the first case as compared with the eight-member metal chelate rings in the second. IR and fluorescence spectroscopy provided additional information about the structure of these complexes.

Automated summary

The complexation behavior of two novel, chiral pinene-bipyridine-type ligands towards lanthanide ions was investigated, and the ligand with a shorter carboxylic arm formed more stable complexes compared to the ligand with a longer carboxylic arm. IR and fluorescence spectroscopy provided additional information about the structure of these complexes.