Circularly Polarized Luminescence from an Eu(III) Complex Based on 2‑Thenoyltrifluoroacetyl-acetonate and a Tetradentate Chiral Ligand

A new chiral complex {[Eu<b>L</b>(tta)₂(H₂O)]­CF₃SO₃; <b>L</b> = <i>N</i>,<i>N</i>′-bis­(2-pyridylmethylidene)-1,2-(<i>R</i>,<i>R</i> + <i>S</i>,<i>S</i>)-cyclohexanediamine; tta = 2-thenoyltrifluoroacetyl-acetonate} has been synthesized and characterized from a structural and spectroscopic point of view. The molecular structure in the solid state shows the presence of one chiral <b>L</b>, two tta, and one water molecules bound to the metal center. <b>L</b> and tta molecules can efficiently harvest and transfer to Eu­(III) the UV light absorbed in the 250–400 nm range. The forced electric-dipole ⁵D₀ → ⁷F₂ emission band dominates the Eu­(III) emission spectra recorded in the solid state and in solution of acetonitrile or methanol and the calculated intrinsic quantum yield of the metal ion is around 40–50%. The light emitted by the enantiopure complex shows a sizable degree of polarization with a maximum value of the emission dissymmetry factor (<i>g</i>_lum) equal to 0.2 in methanol solution. If compared with the complex in the solid state or in acetonitrile solution, then the first coordination sphere of Eu­(III) when the complex is dissolved in methanol is characterized by the presence of one CH₃OH molecule instead of water. This fact is related to different Eu­(III) CPL signatures in the two solvents