Stereochemistry and solid-state circular dichroism spectroscopy of eight-coordinate chiral lanthanide complexes

Eight-coordinate chiral lanthanide complexes [Eu(dbm)3L RR ] (1), [Eu(dbm)3L SS ] (2) and [Tb(dbm)3L RR ] (3) (L RR /L SS = (-)-/(+)-4,5-pineno-2,2′-bipyridine, Hdbm = dibenzoylmethane) were synthesized stereoselectively, which were characterized by UV-vis, CD spectra and X-ray single-crystal diffraction. The mirror-image structure features of complexes 1 and 2 were obtained by combination of the solid-state CD spectra and the crystal structure analysis. After further comparison with the solid-state CD spectra of six-coordinate and seven-coordinate metal complexes containing β-diketone ligands, the CD spectra-absolute configuration correlation rule for the eight-coordinate β-diketonate lanthanide complexes was proposed through the exciton chirality method for the first time. The Δ or Λ absolute configurations of complexes 1–3 with the distorted square antiprism geometry were confirmed by the X-ray single-crystal analysis.