Luminescence, CPL and magnetic properties of 1D enantiopure Ln3+ complexes with (S-) and (R-) α-methoxyphenylacetate ligand

Abstract

The reaction of Ln(NO₃)₂·6H₂O (Ln = Eu, Tb, Dy and Sm) with (R)-(−)-α-methoxyphenylacetic acid (R-HMPA) and 1,10-phenanthroline (phen) in EtOH/H₂O allows the isolation of 1D chiral compounds of formula [Ln(μ-R-MPA)(R-MPA)₂(phen)]_n in which Ln = Eu (R-Eu), Tb (R-Tb), Dy (R-Dy) and Sm (R-Sm). The same synthesis by using (S)-(+)-α-methoxyphenylacetic acid (S-HMPA) instead of (R)-(−)-α-methoxyphenylacetic acid allows the isolation of the enantiomeric compounds with formula [Ln(μ-S-MPA)(S-MPA)₂(phen)]_n where Ln = Eu (S-Eu), Tb (S-Tb), Dy (S-Dy) and Sm (S-Sm). Single crystal X-Ray diffraction measurements were performed for compounds R/S-Eu, R/S-Tb, S-Dy and S-Sm. The luminescence and the circular dichroism measured in the solid state are reported. All compounds show sensitized luminescence, notably the Eu³⁺ and Tb³⁺ ones, whose emission color can be perceived by the naked eye. For the Eu³⁺ and Tb³⁺ derivatives the quantum yield and the circular polarized luminescence have been measured. For the magnetic allowed transition ⁵D₀ → ⁷F₁ of the Eu³⁺ compound, the anisotropy factor g_lum is ±0.013 (+for S-Eu). Also, magnetic properties of all compounds were studied with the Dy³⁺ analogue showing slow relaxation of the magnetization under a direct current magnetic field of 1000 Oe.