Homochiral luminescent lanthanide dinuclear complexes derived from a chiral carboxylate

Abstract

A new family of homochiral lanthanide dinuclear complexes based on a chiral carboxylate, namely [Ln(R-pba)₃(phen)]₂ (Ln = La (1), Ce (2), Pr (3), Nd (4), Sm (5), Eu (6), Gd (7), Tb (8), Dy (9) and Ho (10), R-pba = (R)-2-phenylbutyric acid, phen = 1,10-phenanthroline), have been synthesized and structurally characterized by single-crystal X-ray diffraction, elemental analyses and IR spectra. Complexes 1–10 are isostructural and crystallize in the chiral space group P2₁. Their optical activity and enantiomeric nature were confirmed by the circular dichroism spectra. Complexes 6, 8 and 9 exhibit strong fluorescent emissions with typical narrow emission bands of lanthanide ions and 6 and 8 display relatively high quantum yields. Magnetic investigations revealed that the weak antiferromagnetic exchange and/or the depopulation of the Ln(III) excited Stark sub-levels which exist in 7–10.