SYNTHESIS AND CHARACTERIZATION OF CHIRAL 18-MEMBERED-MACROCYCLE LANTHANIDE COMPLEXES - CIRCULAR-DICHROISM AND CIRCULARLY POLARIZED LUMINESCENCE

New chiral 18-membered lanthanide-macrocycle complexes were prepared from lanthanide nitrates, 2,6-pyridinedicarboxaldehyde, and chiral 1,2-diaminocyclohexane by template reaction, where the lanthanides are lanthanum(III), europium(III), and terbium(III) ions. The structures of these complexes were characterized by NMR and luminescence spectroscopy to have D2 molecular symmetry. Strong circularly polarized luminescence was also detected for the Eu(III) and Tb(III) complexes due to the twisted conformation. The absolute chiral structures were determined from CD data. The intramolecular energy-transfer processes were found to occur between pi* electronic states of the ligand and 4f levels of the central lanthanide ions in the Eu(III) and Tb(III) complexes. In addition, a photodecomposition reaction was studied under strong UV laser radiation.