Photophysical and Chiroptical Properties of the Enantiomers of ,'-Bis(1-phenylpropyl)-2,6-pyridinecarboxamide and their Chiral 9-Coordinate Ln Complexes.

The , and , enantiomers of ,'-bis(1-phenylpropyl)-2,6-pyridinedicarboxamide, , react with Ln ions (Ln = La, Eu, Gd, and Tb) to give stable [Ln((,)- and (,)-))] in anhydrous acetonitrile solution, as evidenced by various spectroscopic measurements, including NMR and luminescence titrations. In addition to the characteristic Eu and Tb luminescence bands, the steady-state and time-resolved luminescence spectra of the aforementioned complexes show the residual ligand-centered emission of the ππ* to ππ* states, indicating an incomplete intersystem crossing (ISC) transfer from the ππ* to ππ* and ligand-to-Ln energy transfer, respectively. The high circularly polarized luminescence (CPL) activity of [Eu()] confirms that using a single enantiomer of induces the preferential formation of one chiral [Eu()] complex, consistent with the [Eu ] complexes formed with other ligands derived from a 2,6-pyridine dicarboxamide moiety. Furthermore, the CPL sign patterns of complexes with (,) or (,) enantiomer of are consistent with the CPL sign pattern of related [Ln ] complexes with the (,) or (,) enantiomer of the respective ligands in this family.